JPH06346946A - Vulcanizable rubber composition and transmission belt using it - Google Patents

Abstract

PURPOSE:To simultaneously improve not only a heat resisting curved travelling life span of a toothed belt but also a freezing resisting curved travelling life span and to stably use it under a high load condition, a small pulley condition and under a condition of violent rise and fall of environmental temperature and others. CONSTITUTION:At least either one of a back rubber part 1 and a tooth rubber part 2 constituting a toothed belt A is formed of a vulcanizable rubber component constituted by respectively mixing a liquid NBR 2-10 weight part and a plasticizer 0-8 weight part against an ethylene unsaturated nitryl conjugate dienehighly saturated rubber 100 weight part in which the content of a conjugate diene unit in an aggregate chain is 30 weight % or less and excellent in curve resisting fatigue and freezing resisting properties.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vulcanizable rubber composition having excellent bending fatigue resistance and cold resistance, and a power transmission belt formed using the same.

[0002]

2. Description of the Related Art Recent transmission belts such as toothed belts and V-ribbed belts are required to withstand use under severe conditions such as high load conditions, small pulley conditions, and rising or falling atmospheric temperature.

As a toothed belt which meets such a demand, a toothed belt having a back rubber portion and a tooth rubber portion formed of, for example, a sulfur-containing cross-linked rubber composition of hydrogenated nitrile rubber has hitherto been proposed. Even if it does not exhibit sufficiently satisfactory characteristics, it has been considerably improved in heat resistance as compared with the previous toothed belt (see, for example, JP-A-60-172749).

[0004]

However, it is difficult to say that the above-mentioned toothed belt has sufficient flexural fatigue resistance and cold resistance apart from heat resistance, and it is difficult to say that this is, for example, for use in cold regions. When used as a timing belt for automobiles, satisfactory results cannot be obtained in terms of cold flex running life, and with transmission belts such as this kind of toothed belt, not only heat flex running life but also cold flex running It was desired to develop a transmission belt that is well-balanced and has a long service life.

The present invention has been made in view of the above points, and an object thereof is to provide a rubber composition excellent not only in heat resistance but also in flex fatigue resistance and cold resistance. In addition to heat-resistant flexing running life, cold flexing running life can be satisfied at the same time with a well-balanced transmission belt, which can be stably used even under severe conditions such as high load conditions, small pulley conditions, and rising or falling atmospheric temperature. To do so.

[0006]

In order to achieve this object, the vulcanizable rubber composition according to the invention of claim 1 has ethylene having a conjugated diene unit content in the polymer chain of 30% by weight or less. Unsaturated nitrile-conjugated diene-based highly saturated rubber 1
It is characterized by mixing 2 to 10 parts by weight of liquid NBR and 0 to 8 parts by weight of a plasticizer with respect to 00 parts by weight.

Further, the transmission belt according to the invention of claim 2 is characterized in that at least a part thereof is constituted by the vulcanizable rubber composition according to the invention of claim 1.

[0008]

According to the invention of claim 1, the vulcanizable rubber composition has a content of conjugated diene units in the polymer chain of 30% by weight or less, and is an ethylenically unsaturated nitrile-conjugated diene-based highly saturated rubber 100. Since 2 to 10 parts by weight of liquid NBR and 0 to 8 parts by weight of a plasticizer are blended with respect to 1 part by weight, not only the heat-resistant flex life of this vulcanizable rubber composition but also the cold flex life. Also improves. In addition, in the blending of the vulcanizable rubber composition, the reason why the liquid NBR is 2 to 10 parts by weight and the plasticizer is 0 to 8 parts by weight is that the liquid NBR is less than 2 parts by weight or more than 10 parts by weight. If the amount of the plasticizer exceeds 8 parts by weight, the bending fatigue resistance and cold resistance tend to be poor, which is not desirable.

Further, in the invention of claim 2, since at least a part of the transmission belt is made of the vulcanizable rubber composition, the heat resistance bending running life as well as the cold bending resistance life is simultaneously satisfied with good balance. It can be used as a transmission belt that can be stably used even under severe conditions such as a high load condition, a small pulley condition, and an increase / decrease in ambient temperature.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a toothed belt A according to an embodiment of the present invention. The toothed belt A includes a back rubber portion 1 and a plurality of tooth rubber portions 2 integrally provided on the back rubber portion 1. A core body 3 embedded between the back rubber portion 1 and the tooth rubber portion 2, and a reinforcing canvas 4 arranged on the tooth rubber portion 2 side. At least one of the rubber portions 2 is formed by using a rubber composition as a shape-retaining elastomer. In the actual manufacturing of the power transmission belt, the back rubber part 1 and the tooth rubber part 2 are integrally formed of the same material, and therefore, normally, all the parts are integrally formed of the rubber composition. Will be done.

In the above rubber composition, 100 parts by weight of the ethylenically unsaturated nitrile-conjugated diene-based highly saturated rubber having a content of conjugated diene units in the polymer chain of 30% by weight or less is used as a liquid NBR. 2 to 10 parts by weight and a plasticizer to 0 to 8 parts by weight, respectively. 2 to 10 parts by weight of liquid NBR is added to 100 parts by weight of an ethylenically unsaturated nitrile-conjugated diene-based highly saturated rubber having a content of conjugated diene units in the polymer chain of 30% by weight or less, and plasticization is performed. The reason why the agent is blended in an amount of 0 to 8 parts by weight is that the liquid NBR is less than 2 parts by weight or more than 10 parts by weight, or the plasticizer is more than 8 parts by weight, the flex fatigue resistance and This is because the cold resistance tends to decrease, which is not preferable.

The toothed belt obtained by the above embodiment is
Since a part or all of the rubber material constituting portion is composed of the above rubber composition, the belt itself is provided with excellent properties such as a heat-resistant flex life and a cold flex life. Therefore, in actual use, it shows excellent heat and cold flexing life,
It can be used stably even under severe conditions such as small pulley conditions and rising or falling of ambient temperature.

Needless to say, the present invention can be applied to other transmission belts such as V-ribbed belts.

Next, a specific example of the present invention will be described. The upper part of Table 1 shows the component compositions of the rubber compositions used in Examples 1 to 5 of the present invention and Comparative Examples 1 to 4 based on the above examples. An unvulcanized sheet having a predetermined thickness is prepared and prepared in advance from each of these rubber compositions. Then, an endless polyamide canvas cloth is put on the peripheral surface of a cylindrical mold having tooth-forming cavities formed at predetermined intervals in the circumferential direction and extending in the longitudinal direction. After spirally winding a glass cord as a core body in the circumferential direction, and then winding the above-mentioned unvulcanized sheet on it, press-molding and vulcanizing it in a pressure cooker, and then cutting it into a predetermined width To obtain a toothed belt.

Other various characteristic values such as hardness, tensile strength and elongation of each toothed belt are shown in the lower part of Table 1.

Then, a running test was carried out on these toothed belts on a belt stand, and the heat-resistant flexing running life and cold-flexing running life were examined for each. The results are shown in Table 2.
Shown in.

Of these, regarding the heat-resistant bending running life,
An idler pulley is interposed between the driving pulley and the driven pulley to wind a toothed belt having a width of 19 mm, the rotation speed of the driving pulley is 3000 rpm, and the belt initial tension is 15 kgf.
The toothed belt was run under an unloaded condition at an ambient temperature of 140 ° C., and the time from the start of running until the occurrence of cracks in the toothed belt was evaluated. On the other hand, the cold bending running life was the same as in the heat resistant bending running life test, except that the belt was run at an ambient temperature of -35 ° C. The heat-resistant flexing running life and the cold flexing running life in Table 2 are both defined by the time (H) until crack initiation.
It was obtained by converting the value of Comparative Example 1 to 100 and converting it into an index.

Comparative Example 1 (when neither the plasticizer nor the liquid NBR was mixed with the hydrogenated nitrile rubber composition) was the worst in both the heat-resistant flexing running life and the cold flexing running life. In addition, Comparative Example 2 (when a plasticizer is added to the hydrogenated nitrile rubber composition and no liquid NBR is added) and Comparative Example 3 (when a liquid NBR is added to the hydrogenated nitrile rubber composition and no plasticizer is added) Although the heat-resistant flexing running life and the cold flexing running life are both longer than those in Comparative Example 1 in (), it cannot be said that they are well balanced.

Further, Comparative Example 4 (when both the plasticizer and the liquid NBR were blended with the hydrogenated nitrile rubber composition)
In comparison with Comparative Example 1, a remarkable improvement in cold-bending running life was observed, but no significant improvement in heat-resistant bending running life was observed as compared with the example of the present invention. The reason for this is that the rubber composition of Comparative Example 4 is the closest to the rubber composition of the present invention, and the liquid NBR is 5
By weight (2 to 10 parts by weight in the case of the example of the present invention), but especially 10 parts by weight of the plasticizer (in the case of the example of the present invention
It is considered that the amount of the plasticizer is excessive.

On the other hand, the toothed belts according to Examples 1 to 5 of the present invention (when the hydrogenated nitrile rubber composition was blended with 0 to 8 parts by weight of the plasticizer and 2 to 10 parts by weight of liquid NBR) were comparative examples. It is clear that both the heat resistant bending running life and the cold bending running life are well-balanced and superior to the toothed belts according to 1 to 4. Therefore, the toothed belts according to Examples 1 to 5 of the present invention can be stably used even under severe conditions such as high load conditions, small pulley conditions, and rising or falling of ambient temperature.

[0021]

[Table 1]

[0022]

[Table 2]

[0023]

As described above, according to the vulcanizable rubber composition of the invention of claim 1, the content of the conjugated diene unit in the polymer chain is 30% by weight or less, the ethylenically unsaturated nitrile. -Because 2 to 10 parts by weight of liquid NBR and 0 to 8 parts by weight of a plasticizer are mixed with 100 parts by weight of a conjugated diene-based highly saturated rubber, not only heat resistance but also bending fatigue resistance and A vulcanizable rubber composition having excellent cold resistance can be obtained.

According to the transmission belt of the invention of claim 2, since at least a part of the transmission belt is composed of the vulcanizable rubber composition, the belt itself has not only heat resistance but also bending fatigue resistance and cold resistance. Therefore, there is an effect that not only the heat resistant bending running life but also the cold bending running life can be significantly improved.

[Brief description of drawings]

FIG. 1 is a perspective view of a toothed belt according to an embodiment of the present invention.

[Explanation of symbols]

 A Toothed belt 1 Back rubber part 2 Tooth rubber part 3 Core body 4 Reinforced canvas

Claims (2)

[Claims] 1. A liquid NBR based on 100 parts by weight of an ethylenically unsaturated nitrile-conjugated diene-based highly saturated rubber having a content of conjugated diene units in a polymer chain of 30% by weight or less.
A vulcanizable rubber composition comprising 2 to 10 parts by weight and a plasticizer of 0 to 8 parts by weight, respectively. 2. A transmission belt comprising at least part of the vulcanizable rubber composition according to claim 1.