JPH02286939A - Catapillar belt - Google Patents

Abstract

PURPOSE:To make a tensile strength core body excellent in durability and to lessen the growth due to travel motion by using polyester polymer as its core ingredient and by arranging a cord consisting of core sheath shape complex fiber with polyamide polymer as its sheath compound in the lengthy direction. CONSTITUTION:A tensile strength core body 1 of a non-edge track belt covered with upper and lower part reinforcing cloths 2, 3 and additionally covered with a cover rubber 4 is constituted by arranging a cord made of core sheath shape complex fiber with polyester polymer as its core compound C and polyamide polymer as its sheath compound S in the lengthy direction. Consequently, it is possible to largely improve adhesive property of fiber, prevent adhesive deterioration of polyester polymer and improve chemical resistance stability by separating polyester polymer of low adhesive property from a rubber layer so that polyamide polymer of good adhesive property always contacts the rubber layer by way of covering polyester polymer with the core compound C with polyamide polymer as the sheath compound S.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to endless track belts such as track belts attached to snowmobiles, etc. The present invention relates to a track belt with excellent performance.

[Conventional technology]

Conventionally, track belts are attached to snowmobiles, etc.
That is, as shown in FIG. 2, the structure of the endless track belt is, for example, as shown in FIG.
are arranged in the longitudinal direction of the belt as blind fabrics, upper and lower reinforcing fabrics are laminated on the upper and lower parts of this tensile strength core 1 so as to sandwich 2.3, and are further covered with cover rubber 4. A lug rubber 5 is provided on one side of the cover rubber 4 to assist in driving the sprocket.

Polyester fibers and aramid fibers are preferably used as the tensile strength core of this synthetic fiber multifilament cord.

The reason for this is that the core of a track belt needs to have little growth due to running and high strength, and for this reason, the above-mentioned fibers are preferably used.

[Problem that the invention seeks to solve]

However, polyester fibers have the disadvantage that they have low adhesion to rubber and are easily hydrolyzed by moisture and amines in the rubber. There is a problem in that not only a complicated processing process of applying an adhesive treatment is required, but also significant restrictions are required on the amine generating source (vulcanization accelerator, etc.) in the rubber composition.

Even if such improvements are attempted, the hydrolyzability of polyester is essentially due to its chemical structure, so it has not been possible to significantly improve the durability of track bands using polyester fibers as the core. I can't do that.

On the other hand, aramid fiber, which has superior strength and modulus compared to polyester fiber, has significantly inferior bending fatigue resistance due to the rigidity of its molecules, and also has poor adhesion to rubber, which significantly reduces the durability of the track belt. There's a problem. Moreover, it is much more expensive than other synthetic fibers, and there is a problem in that the product price increases significantly.

For this reason, when using aramid fibers, attempts have been made to significantly increase the number of twists in the cord to improve durability, apply adhesive treatment twice when adhering to rubber, or add adhesive to the rubber. However, these attempts not only reduce strength and modulus but also increase product cost.

On the other hand, from the viewpoint of adhesion with rubber and bending fatigue resistance, polyamide fibers typified by 6-nylon and 66-nylon are the above-mentioned polyesters.

It has clearly superior properties compared to aramid fibers, and its strength is equal to or higher than that of polyester, making it a preferred material.

However, polyamide fibers have a small initial modulus, and when used in the core of a track belt, they grow significantly during running, resulting in large walnuts in the track belt, which not only reduces traction performance but also causes problems during high-speed running. A standing wave phenomenon occurs, resulting in insufficient durability.

In order to solve this problem, attempts have been made to perform heat treatment under a high tensile run during the heat treatment performed when applying adhesive to rubber, but even this does not result in a significant improvement in modulus. In addition, the thermal shrinkage rate increases significantly, which significantly affects product dimensions.

[Purpose of the invention]

The present invention was devised in view of the above-mentioned conventional problems, and an object of the present invention is to provide an endless track belt which is excellent in durability and exhibits little growth due to running.

Growth due to running here means that the endless track belt attached to a snowmobile or the like stretches due to running, and as a result, traction performance deteriorates.

[Means to solve the problem]

In order to achieve the above object, the present invention uses a polyester polymer as the core component C in the endless track belt of an endless track band in which the upper and lower parts of the tensile core are covered with reinforcing cloth and further covered with cover rubber. It is characterized by being constructed by arranging cords made of core-sheath type conjugate fibers in the longitudinal direction with polyamide polymer as the sheath component S.

[Action of the invention]

This invention is constructed as described above, and by covering the core component polyester polymer with a polyamide polymer as a sheath component, the polyester polymer with low adhesiveness is isolated from the rubber layer, and the adhesive property is improved. This allows the polyamide polymer, which has good properties, to be in constant contact with the rubber layer, which greatly improves the adhesion of the fibers, prevents the adhesive deterioration of the polyester polymer, and provides chemical resistance. This eliminates the drawback of low stability.

The core-sheath type composite fiber used in the present invention is, for example, the first
As shown in the figure, it has a core component C at the center of the single fiber cross section,
It has a form in which the sheath component S surrounds it, and this has a similar form in the longitudinal direction of the fiber.

The number of core components C present in the sheath component S may be one as shown in FIG. 1, or may be two or more.

In this core-sheath type composite fiber, the core component C needs to be made of a polyester polymer, and the sheath component S needs to be made of a polyamide polymer. That is, by covering the polyester polymer of the core component C with a polyamide polymer as the sheath component S, the polyester polymer with low adhesiveness is isolated from the rubber layer, and the polyamide polymer with good adhesiveness is formed. can be kept in constant contact with the rubber layer, which greatly improves the adhesion of the fibers, prevents the adhesion of polyester polymers from deteriorating, and overcomes the disadvantage of low chemical stability. It can be resolved.

As the polyester polymer constituting the core component C of the core-sheath composite fiber, it is preferable to use polyethylene terephthalate, which is a typical polymer of ethylene terephthalate, as a repeating structural unit of the polymer chain. A polymer with a high degree of polymerization Preferred is polyethylene terephthalate, which has an intrinsic viscosity of at least 0.80 as measured at 25°C using orthochlorophenol as a solvent. This polyethylene terephthalate may be copolymerized with a small amount of a copolymerizable third component such as a carboxylic acid such as isophthalic acid or P-oxybenzoic acid or a derivative thereof.

In addition, as the polyamide-based polymer of the sheath component S, 66 nylon (polyhexamethylene adipamide), 6 nylon (polycaprolactam), 46 nylon (polytetramethylene adipamide), and their co-products are used as the sheath component S. Examples include polymers. Among these,
Particularly preferred is 66 nylon, which has a high melting point close to that of polyester polymers and a relative viscosity of at least 2.8 in sulfuric acid at 25°C. The composite ratio of the core-sheath type composite fiber (the cross-sectional area ratio of the core component C and the sheath component S) is set so that the effect of improving the adhesion and chemical stability of the polyester polymer of the core component C to rubber is as large as possible, Moreover, it may be selected within a range that minimizes the decrease in modulus as much as possible.

This composite ratio is not particularly limited, but the core:
The sheath cross-sectional area ratio is 90:10 to lO:90, preferably 8
0:20-20:80, more preferably 70:3
It is appropriately selected within the range of 0 to 30 near 0. If the ratio of the sheath component S is too small and the core component C is too large, the polyester polymer of the core component C will be exposed, and the adhesiveness to rubber and chemical deterioration resistance will decrease. Undesirable. On the other hand, if the sheath component S becomes too large, the proportion of the polyamide polymer becomes excessive, the modulus of the fiber cord becomes low, and growth due to running increases.

The core-sheath composite fiber used in the present invention is preferably obtained by a high-speed spinning method in which the spinning speed is at least 2000 m/min, preferably 3000 m/min or more. This is because by applying this high-speed spinning method, the bonding (adhesion) force between the core component C made of a polyester polymer and the sheath component S made of a polyamide polymer is improved. Although the reason for this is not clear, the crystallization of the two polymers,
The crystallization of the polyamide polymer, which is particularly prone to crystallization, is suppressed due to high-speed spinning, and its polymer chains are oriented in the fiber axis direction, and at the same time, the polyester polymer of the core component C is oriented in the fiber axis direction. This is presumed to be due to the fact that stress concentration at the bonding interface between the two components during spinning and drawing processes is significantly suppressed.

A plurality of filaments made of the core-sheath composite fibers are converged and twisted to form a fiber cord. The twist given to this fiber cord is K=74D (in the above formula, K is the twist coefficient, T is the number of twists (twice/10 cd),
D indicates the total denier of the cord), and the twist coefficient is in the range of 1000 to 2500, preferably 1500 to 2.
It is preferable that it be in the range of 000. If the twist coefficient is less than 1000, not only the bending fatigue resistance will be reduced, but also the convergence of the cord will be reduced, resulting in poor adhesion to rubber. On the other hand, when the twist coefficient exceeds 2,500, the modulus and strength decrease significantly, and the running growth of the endless track belt increases.

This twisted fiber cord is made into a blind-like fabric and then treated with an adhesive.

Here, the adhesive used for adhesive treatment is resorcinol, which is usually used for bonding polyamide fibers and rubber.
A so-called RFL (mixture of a resorcinol/formaldehyde initial condensate and rubber latex), which is a mixture of a formaldehyde initial condensate and rubber latex, is used.

Also, after applying the adhesive, 1-3 times at 100-160°C.
After drying for minutes, a heat treatment is applied at 200''C to 250C for 30 seconds to 3 minutes under a tension of 0.1-1.0 g/d.

2゜25 g of the cord subjected to adhesive heat treatment in this way
The elongation at /d must be 8% or less, and the dry heat shrinkage rate at 150°C must be 5% or less.

Here, if the elongation at 2.25 g/d is more than 8%, the initial modulus will be too low and the growth due to running will be large.

Further, if the dry heat shrinkage rate exceeds 5%, dimensional changes during production of the endless track belt become large, and at the same time, the initial modulus of the core decreases.

Further, there are no particular restrictions on the type and amount of the cord rubber in which the tensile core is embedded, the amine vulcanization accelerator used to vulcanize it, and the anti-aging agent.

Examples are shown below.

〔Example〕

The composite ratio of polyethylene terephthalate as the core component C and 66 nylon as the sheath component S is 50150 in terms of cross-sectional area ratio.
1500d core-sheath composite fiber filament and 70/
30 1500 d core-sheath type composite fiber filaments were each twisted to a predetermined value to form a two-stranded cord.

For comparison, 1500d polyester fiber and 1
The 260d 66 nylon fibers were also twisted to form a two-strand cord.

Using these cords, blind fabrics were made with a number of 55 cords/5 C1 and subjected to adhesive heat treatment.

Core-sheath composite fiber cords and 66 nylon cords were treated with RFL (a mixture of resorcinol formaldehyde initial condensate and rubber latex), while polyester cords were treated with Vulnax's polyester adhesive “Vulkabond”. A two-bath treatment was performed in which the sample was pretreated with E'' and then treated with RF.

After drying the adhesive at a heat treatment temperature of 130''C, baking was performed at a predetermined temperature shown in Attached Table 1.

The tension during heat treatment is shown in Attached Table 1, and the tension conditions were varied for the core-sheath type composite fiber.

After coating the thus obtained bonded and heat-treated bamboo blind fabric with a natural rubber-based rubber composition, a track belt having the cross-sectional shape shown in Figure 2 was made, and an actual vehicle durability test was conducted. I did.

The evaluation is based on the tensile strength of the adhesive-treated blind fabric cord and 2
．． The dry heat shrinkage rate at an intermediate elongation of 150°C at 25 g/d, the strong retention rate of the cord taken from the core after the actual vehicle durability test, the peel adhesion test between the core and the cover rubber, and the results before and after running. The dimensional changes of the track belt were measured.

The above results are shown in Table 1.

(Leaving space below) As shown in Examples 1.2 and 3 of Table 1, the product of the present invention has the same growth performance and clear durability as compared to the track belt with a polyester core of Conventional Example 1. Excellent,
Furthermore, compared to the nylon core product of Conventional Example 2, it can be seen that although the durability is almost the same, the growth property is clearly superior.

On the other hand, even if a core-sheath type composite fiber cord is used as shown in Comparative Example 1, when the intermediate elongation is more than 8%, the growth performance is significantly inferior.

Further, in Comparative Example 2, since the dry heat shrinkage rate was more than 5%, the product after vulcanization was significantly smaller than the designed dimensions, and could not be used for testing.

〔Effect of the invention〕

This invention provides the tensile strength core of the endless track belt as described above.
It is composed of a core-sheath composite fiber with a polyester polymer as a core component and a polyamide polymer as a sheath component, and the fibers are arranged in the longitudinal direction, resulting in the following excellent effects. It is something.

(a) An endless track belt with excellent durability can be obtained.

(b) It is possible to form an endless track belt with low growth potential.

(C) The degree of freedom in rubber compounding is large (Dip processing can be simplified, so a track belt with excellent productivity can be obtained.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a core-sheath type composite fiber according to the present invention, and FIG. 2 is a sectional view of a track belt. 1... Synthetic fiber multifilament cord tensile strength core, 2, 3... Upper and lower reinforcing cloth, 4... Cover rubber, 5...
...Lag rubber, C...core component, S...sheath component. Diagram

Claims (1)

[Claims] In an endless track belt in which the upper and lower parts of a tensile core are covered with reinforcing cloth and further covered with cover rubber, the tensile core has a polyester polymer as a core component and a polyamide polymer as a sheath component. Consisting of core-sheath composite fibers,
An endless track belt characterized by being constructed by arranging these fibers in the longitudinal direction.