JPH05271472A - Rubber composition and driving belt made from the same - Google Patents

Abstract

PURPOSE:To obtain a rubber compsn. sufficiently improved in tensile strength, flexural fatigue resistance, tear strength, permanent compression set, abrasion resistance and heat resistance, and a driving belt made using the rubber compsn. which belt is satisfactory in respect of edgewise pressure resistance and reduction in obnoxious noise. CONSTITUTION:A rubber compsn. comprises 100 pts.wt. hydrogenated rubber of an ethylenically unsatd. nitrile-conjugated diene copolymer, 10-100 pts.wt. metal salt of an unsatd. carboxylic acid, 0.2-10 pts.wt. org. peroxide, 0.4-1.0 pts.wt. sulfur component, and 0-15 pts.wt. staple fiber, provided that the molar amt. of the sulfur component is larger than that of the org. peroxide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition capable of imparting excellent strength characteristics and fatigue characteristics, and a power transmission belt using the rubber composition.

[0002]

2. Description of the Related Art Recently, transmission belts such as toothed belts and V-ribbed belts have been required to withstand use under high load conditions. Then, as a rubber composition whose physical properties are modified to meet such requirements, it is composed of an ethylenically unsaturated nitrile-conjugated diene-based copolymer as disclosed in, for example, Japanese Patent Application Laid-Open No. 1-311158. It has been proposed to improve the tensile strength by mixing hydrogenated rubber with zinc methacrylate and an organic peroxide. It should be noted that this rubber composition contains no sulfur component.

On the other hand, as a general rubber composition, an existing rubber such as EPR (ethylene propylene rubber) mixed with an organic peroxide is prepared by adding a sulfur component having an equimolar atom to the organic peroxide. It has been conventionally known that a sulfur component acts as a co-crosslinking agent when it is crosslinked with an organic peroxide so as to improve bending fatigue resistance and tear strength.

[0004]

However, although the former rubber composition is excellent in tensile strength, it is not always satisfactory in flex fatigue resistance and tear strength.

On the other hand, in the latter general rubber composition, although the flex fatigue resistance and the tear strength are excellent, the compression set and the heat resistance decrease when the amount of the sulfur component added increases,
In addition, since the tensile strength tends to deteriorate, there is a limit to the amount of sulfur component added, and it is necessary to further improve bending fatigue resistance and tear strength so that it can withstand use under high load conditions. However, it is the current situation that I do not trust it.

The present invention has been made in view of the above points, and an object of the present invention is to increase tensile strength and flex resistance by adding an appropriate amount of a sulfur component or short fibers to the former rubber composition. Another object of the present invention is to provide a rubber composition capable of sufficiently improving fatigue resistance, tear strength, compression set, heat resistance and the like, and a transmission belt using the same.

[0007]

In order to achieve the above object, the first solution of the present invention is a hydrogenated rubber comprising an ethylenically unsaturated nitrile-conjugated diene copolymer; 10
0 parts by weight, unsaturated carboxylic acid metal salt; 10 to 100 parts by weight, organic peroxide; 0.2 to 10 parts by weight and sulfur component;
That is, the rubber composition is constituted by containing 0.4 to 1.0 part by weight and converting the sulfur component into the number of moles to be more than the organic peroxide.

A second solving means of the present invention is that the rubber composition in the first solving means is used for at least a part of a belt-constituting rubber portion of a transmission belt.

The third means of solving the present invention is to provide a hydrogenated rubber comprising an ethylenically unsaturated nitrile-conjugated diene copolymer; 100 parts by weight; unsaturated carboxylic acid metal salt;
This is because the rubber composition was constituted by including 100 parts by weight, 0.2 to 10 parts by weight of organic peroxide and 0 to 15 parts by weight of short fibers.

A fourth solution means of the present invention is that the rubber composition according to the third solution means is used for at least a part of a belt-constituting rubber portion of a transmission belt.

The fifth means for solving the present invention is to provide a hydrogenated rubber comprising an ethylenically unsaturated nitrile-conjugated diene copolymer; 100 parts by weight; unsaturated carboxylic acid metal salt;
00 parts by weight, organic peroxide; 0.2 to 10 parts by weight, sulfur component; 0.4 to 1.0 part by weight and short fiber; 0 to 15 parts by weight, and the sulfur component is converted to the number of moles. That is, the rubber composition was constituted by containing more than the organic peroxide.

A sixth solving means of the present invention is that the rubber composition according to the fifth solving means is used for at least a part of a belt-constituting rubber portion of a transmission belt.

A seventh solution means of the present invention is that the short fiber content is set to 2 to 7.5 parts by weight in the third and fifth solution means.

An eighth solving means of the present invention is that, in the fourth and sixth solving means, the content of the short fibers is set to 2 to 7.5 parts by weight.

The ninth means of solving the problems of the present invention is to solve
And 7 the rubber hardness after vulcanization (JIS
K type 6301 for spring type hardness test)
That is to say ~ 75 °.

The tenth means for solving the problems of the present invention is the second, fourth,
In the solution means of 6 and 8, at least a part of the rubber component of the belt has a rubber hardness (A type in the JIS K 6301 spring hardness test) of 65 to 75 °.

[0017]

With the above-mentioned structure, in the first to tenth means of the present invention, hydrogenated rubber, unsaturated carboxylic acid metal salt and organic peroxide are further added, and the sulfur component is converted into the number of moles of the organic peroxide. Since it is added in an amount larger than that of the product or short fibers are added, the bending fatigue resistance is improved, and particularly the tear strength is further improved as compared with the case of co-crosslinking a general rubber such as EPR. Further, in general rubber, the addition of the sulfur component lowers the compression set, heat resistance and tensile strength, but the present invention does not.

Particularly, in the seventh and eighth means for solving the problem that the short fiber content is specified to be 2 to 7.5 parts by weight, the balance between the wear resistance and the bending fatigue resistance is further excellent and the abnormal noise is generated. It is suitable for a V-ribbed belt because it has a small amount and a reduced friction coefficient.

Further, in the ninth and tenth means for solving the problems, the rubber hardness (A type of JIS K 6301 spring type hardness test) is specified to be 65 to 75 °, whereby bending fatigue resistance and wear resistance are improved. Both were very satisfied with the results.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a V-ribbed belt A as a transmission belt. The V-ribbed belt A includes a plurality of core wires 1, 1,
Is provided with an adhesive rubber layer 2 embedded therein, a back rubber layer 3 is provided on the upper surface of the adhesive rubber layer 2, and four ribs 4 are provided on the lower surface.
A rib rubber layer 5 having 4, ... Is integrally formed, and a rib cloth 6 is integrally adhered to the rib surface of the rib rubber layer 5 with an adhesive (not shown).

The back rubber layer 3 and the rib rubber layer 5 are hydrogenated rubber composed of an ethylenically unsaturated nitrile-conjugated diene copolymer; 100 parts by weight, unsaturated carboxylic acid metal salt;
10 to 100 parts by weight and organic peroxide; based on 0.2 to 10 parts by weight, and optionally sulfur component;
4 to 1.0 parts by weight and / or short fibers; 0 to 15 parts by weight of a rubber composition. When the sulfur component is contained, its content is converted to the number of moles so that it is larger than that of the organic peroxide. The back rubber layer 3 and the rib rubber layer 5 have a rubber hardness (JIS K
6301 spring type hardness test A type) is 65-75
It is set to °.

The hydrogenated rubber comprising an ethylenically unsaturated nitrile-conjugated diene copolymer is an ethylenically unsaturated nitrile such as acrylonitrile or methacrylonitrile,
A rubber obtained by adding hydrogen to a copolymer of a conjugated diene such as 1,3-butadiene, isoprene, and 1,3-pentadiene to saturate the double bond present in the conjugated diene monomer unit. That is. For example, hydrogenated acrylonitrile butadiene rubber (hereinafter abbreviated as H-NBR) obtained by hydrogenating a copolymer of acrylonitrile and 1,3-butadiene can be mentioned. Taking this as an example, H-NB
The ratio of acrylonitrile rubber monomer unit in R is 1
0 to 60% by weight, and the ratio of conjugated diene monomer units is set to 30% by weight or less by means of partial hydrogenation or the like. Also, H-
The molecular weight, glass transition temperature, hydrogenation rate and the like of NBR are not particularly limited, but usually, the hydrogenation rate of the double bond of the conjugated diene monomer unit is 10 to 99%, preferably 80.
~ 95% is good.

The unsaturated carboxylic acid metal salt is an ionic bond between an unsaturated carboxylic acid having a carboxyl group and a metal, and is preferably zinc acrylate or zinc methacrylate. The content of this unsaturated carboxylic acid metal salt is set to 10 to 100 parts by weight with respect to 100 parts by weight of hydrogenated rubber, and the effects as expected below 10 parts by weight and above 100 parts by weight are obtained. Because you cannot do it. Further, the ratio of the hydrogenated rubber to the unsaturated carboxylic acid metal salt is preferably set to 100/100 ≧ hydrogenated rubber / unsaturated carboxylic acid metal salt ≧ 100/15. The reason for setting such a range is that if it is less than 100/15, the strength properties are poor, whereas if it exceeds 100/100, the bending fatigue resistance and impact resilience are poor, and the hardness increase is large.

The organic peroxide is used as a cross-linking agent for hydrogenated rubber, for example, benzoyl peroxide, lauroyl peroxide, ditertiary butyl peroxide, acetyl peroxide, tert-butyl peroxybenzoic acid, dicumyl peroxide. , Diazo compounds such as peroxybenzoic acid, tertiary butyl peroxypivalate and azobisisobutyronitrile are preferred. These organic peroxides may be used alone or in combination. The content of this organic peroxide is set to 0.2 to 10 parts by weight with respect to 100 parts by weight of hydrogenated rubber. This is because sufficient rubber elasticity cannot be obtained if it exceeds the area.

The sulfur component is a so-called co-crosslinking agent, which is a vulcanizing agent used in combination with organic peroxide vulcanization, and is used in the form of sulfur, a sulfur compound and a mixture of sulfur and a sulfur compound. The content of this sulfur component is set to 0.4 to 1.0 parts by weight with respect to 100 parts by weight of hydrogenated rubber in order to improve the bending fatigue resistance, and 0.4 parts by weight is also used. If it is less than 1.0 part by weight or more than 1.0 part by weight, the tear strength is lowered. Further, in general, the addition of a sulfur component is accompanied by an increase in compression set, or the addition of a large amount decreases the crosslinking efficiency and promotes a large increase in hardness during heat aging. Although the number of moles is controlled to be equimolar to that of the oxide, in the present invention, the sulfur component is contained in a larger amount than the organic peroxide in terms of moles. In particular, it is preferable to add about 2.5 to 5 times the molar atom of the organic peroxide because the crosslinking effect can be sufficiently exhibited.

The short fibers include, for example, polyester short fibers, nylon short fibers, and aramid short fibers, and are added especially for improving lateral pressure resistance and reducing the friction coefficient. In addition, its content is short fiber;
The reason why it is set to 0 to 15 parts by weight is that workability such as kneading is taken into consideration, and if it exceeds 15 parts by weight, bending fatigue resistance and heat resistant running life are reduced. Particularly, when the content of the short fibers is 2 to 7.5 parts by weight, the remarkable effect is exhibited.

As the adhesive agent for adhering the rib cloth 6 and the rib rubber layer 5 to the rib rubber layer 5, a material containing a composition of the same type as the rubber composition of the back rubber layer 3 and the rib rubber layer 5 is used. Ethylenically unsaturated nitrile such as NBR-
Although it is a hydrogenated rubber composed of a conjugated diene-based copolymer, the same rubber composition as the rib rubber layer 4 and the like may be used.

The rubber hardness of the back rubber layer 3 and the rib rubber layer 5 (A in the spring type hardness test of JIS K 6301)
The shape is set to 65 to 75 ° because the bending fatigue resistance and wear resistance are excellent in this range.

In the rubber composition of the present invention, a reinforcing agent such as carbon black or silica, together with the above components,
Various agents commonly used in the rubber industry such as fillers such as calcium carbonate and talc, crosslinking aids, vulcanization accelerators, plasticizers, stabilizers, processing aids, antioxidants, colorants, etc. It is appropriately blended according to.

Next, examples of the present invention will be specifically described.

Example 1 The H-NBR compositions shown in Table 1 were kneaded in a Banbury mixer and then rolled by a calender roll to give an unvulcanized rubber sheet. It was vulcanized for 30 minutes to obtain a vulcanized rubber sheet. Properties of this vulcanized rubber sheet are shown in Table 1 and FIG. Further, by using the unvulcanized rubber sheet for the back rubber layer 3 and the rib rubber layer 5, a plurality of core wires 1, 1, ... Are embedded in the adhesive rubber layer 2 and the rib cloth 6 is provided as shown in FIG. To produce a V-ribbed belt A in which the rib surface of the rib rubber layer 5 is adhered by an adhesive,
The time until the occurrence of cracks was investigated. The results are shown in Table 1.

[0033]

[Table 1]

As a result, when EPR was co-crosslinked (see FIG. 3).
Flexural fatigue resistance and tear strength were improved compared to the data of 1.), and the tear strength was further improved. Further, in EPR, compression set, heat resistance and tensile strength were lowered by the addition of the sulfur component, but they were not lowered in the examples of the present invention. From the above data, it can be seen that the characteristics are excellent when the sulfur component is 0.4 to 1.0 part by weight, particularly 0.4 to 0.7 part by weight. This range corresponds to about 2.5 to 5 times the number of moles of the organic peroxide in terms of number of moles. The high temperature load endurance life (time until cracks in the rib rubber layer 5) of the V-ribbed belt A was several times superior to that of the comparative example.

(Example 2) Using the H-NBR compositions shown in Table 2, a V-ribbed belt A was produced in the same manner as in Example 1, and the abrasion resistance test, flex fatigue running life and elongation after heat aging were performed. The retention rate was investigated. The results are shown in Table 2.

[0036]

[Table 2]

As a result, the wear resistance test, the bending fatigue running life, and the elongation retention rate after heat aging were all better in the inventive examples than in the comparative examples. This means that the sulfur content is 0.4
It is shown that the characteristics are excellent when the amount is up to 1.0 part by weight.

(Example 3) Using the H-NBR compositions shown in Table 3, a V-ribbed belt A was prepared in the same manner as in Example 1, and the abrasion resistance test, bending fatigue running life, heat resistant running life and abnormal The degree of sound generation was examined. The results are shown in Table 3.

[0039]

[Table 3]

As a result, the wear resistance test, the bending fatigue test, the heat resistant running life and the degree of abnormal noise were all excellent in the present invention example as compared with the comparative example. Especially, the short fiber content is 2
A remarkable effect was exhibited when the amount was up to 7.5 parts by weight.

Example 4 A V-ribbed belt A was produced using the H-NBR compositions shown in Table 4 in the same manner as in Example 1, and the abrasion resistance test and the bending fatigue running life were examined. The results are shown in Table 4.

[0042]

[Table 4]

As a result, in the comparative examples, unfavorable results were obtained in one or both of the wear resistance test and the bending fatigue running life, but in the examples of the present invention, both were excellent. And
In the examples of the present invention in which excellent results were obtained, the rubber hardness (JIS
K 6301 spring type hardness test A type) is 65-
It was 75 °. That is, in the example of the present invention, the wear resistance and the bending fatigue resistance can be improved with a low rubber hardness as compared with the comparative example.

In each of the above embodiments, the transmission belt is V
Although the ribbed belt A is shown, the invention is not limited to this.
It may be a toothed belt or a V-belt.

[0045]

As described above, according to the present invention according to claims 1 to 10, hydrogenated rubber comprising an ethylenically unsaturated nitrile-conjugated diene copolymer; 100 parts by weight,
Unsaturated carboxylic acid metal salt; 10 to 100 parts by weight and organic peroxide; 0.2 to 10 parts by weight, and further sulfur component;
Since 0.4 to 1.0 part by weight (more than organic peroxide in terms of number of moles) is added, or short fiber; 0 to 15 parts by weight is added, the tensile strength is , Flexural fatigue resistance, tear strength, wear resistance, compression set and heat resistance can be sufficiently improved.

Particularly, according to the present invention according to claims 7 and 8, since the content of the short fibers is specified to be 2 to 7.5 parts by weight, the abrasion resistance and the lateral pressure resistance can be further improved. ,
Moreover, it is suitable for the V-ribbed belt because it can reduce the generation of abnormal noise and the friction coefficient.

Further, according to the present invention according to claims 9 and 10, since the rubber hardness (A type of JIS K 6301 spring type hardness test) is specified to be 65 to 75 °, flex fatigue resistance and resistance It is possible to obtain a sufficiently satisfactory result in terms of both wear resistance.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a V-ribbed belt.

FIG. 2 is a data diagram showing the influence of a sulfur component on the organic peroxide of H-NBR mixed with zinc methacrylate.

FIG. 3 is a data diagram showing the effect of a sulfur component on the organic peroxide of EPR.

[Explanation of symbols]

 None

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Claims (10)

[Claims] 1. A hydrogenated rubber comprising an ethylenically unsaturated nitrile-conjugated diene copolymer; 100 parts by weight; unsaturated carboxylic acid metal salt; 10 to 100 parts by weight; organic peroxide; 0.2 to 10 Parts by weight and sulfur component; 0.4 to 1.0
A rubber composition comprising a part by weight and containing a sulfur component in an amount larger than that of the organic peroxide in terms of number of moles. 2. A hydrogenated rubber comprising an ethylenically unsaturated nitrile-conjugated diene copolymer; 100 parts by weight, unsaturated carboxylic acid metal salt; 10 to 100 parts by weight, organic peroxide; 0.2 to 10 Parts by weight and sulfur component; 0.4 to 1.0
At least a part of the belt-constituting rubber part is constituted by a rubber composition containing a part by weight and containing a sulfur component in terms of number of moles more than the organic peroxide. Transmission belt. 3. A hydrogenated rubber comprising an ethylenically unsaturated nitrile-conjugated diene copolymer; 100 parts by weight, unsaturated carboxylic acid metal salt; 10 to 100 parts by weight, organic peroxide; 0.2 to 10 Parts by weight and short fibers; 0 to 15 parts by weight. 4. A hydrogenated rubber comprising an ethylenically unsaturated nitrile-conjugated diene copolymer; 100 parts by weight, unsaturated carboxylic acid metal salt; 10 to 100 parts by weight, organic peroxide; 0.2 to 10 A power transmission belt, characterized in that at least a part of the rubber portion constituting the belt is constituted by a rubber composition containing 0 to 15 parts by weight of a short fiber and 0 to 15 parts by weight. 5. A hydrogenated rubber comprising an ethylenically unsaturated nitrile-conjugated diene copolymer; 100 parts by weight, unsaturated carboxylic acid metal salt; 10 to 100 parts by weight, organic peroxide; 0.2 to 10 Parts by weight, sulfur component; 0.4 to 1.0 part by weight and short fiber; 0 to 15 parts by weight, and the sulfur component is contained in a larger amount than the organic peroxide in terms of mole number. A rubber composition characterized by the above. 6. A hydrogenated rubber comprising an ethylenically unsaturated nitrile-conjugated diene copolymer; 100 parts by weight; unsaturated carboxylic acid metal salt; 10 to 100 parts by weight; organic peroxide; 0.2 to 10 Rubber containing 0.4 parts by weight to 0.4 to 1.0 parts by weight of sulfur component and 0 to 15 parts by weight of short fiber, and containing more sulfur component in terms of moles than organic peroxide. A transmission belt, wherein at least a part of a rubber part constituting the belt is composed of the composition. 7. The rubber composition according to claim 3, wherein the content of the short fibers is 2 to 7.5 parts by weight. 8. The power transmission belt according to claim 4, wherein the content of the short fibers is 2 to 7.5 parts by weight. 9. The rubber hardness after vulcanization (JIS K 630
The rubber composition according to claim 1, 3, 5 and 7, characterized in that the A type in the spring type hardness test of 1) is 65 to 75 °. 10. The rubber hardness (A type of JIS K 6301 spring hardness test) of at least a part of the belt-constituting rubber part is 65 to 75 °. The described transmission belt.