JPH083374A - Rubber composition and transmission belt using the same - Google Patents

Abstract

PURPOSE:To obtain the subject composition having dense entanglement of a fluororesin containing a polyfunctional co-crosslinking agent and capable of forming into a fiber with a rubber matrix, remarkably improved in flexural fatigue characteristic and tear strength by adding the resin to a solid rubber. CONSTITUTION:This composition is obtained by adding preferably 1-8 pts.wt. of a fluororesin containing a polyfunetional co-crosslinking agent (e.g. trimethylolpropane triacrylate or divinylbenzene) and capable of forming into a fiber to a solid rubber (e.g. butadien rubber or isoprene rubber). Furthermore, the polyfunctional co-crosslinking agent is preferably used in an amount of 0.2-1 pts.wt. based on 1 pts.wt. of the fluororesin. When the polyfunctional co-crosslinking agent is solid, preferably, the crosslinking agent is ground into powder having <=100mum size and then mixed with the fluororesin using a dispersing agent such as molybdenum disulfide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a rubber composition and a transmission belt using the same, and more particularly to measures for improving bending fatigue characteristics and tear strength.

[0002]

2. Description of the Related Art Naturally, rubber products that are highly mechanically stimulated are required to have improved mechanical fatigue resistance.
For example, transmission belts for automobiles are required to be narrower, quieter and have a longer life with higher output of the engine. In order to realize these, high performance and long life of the belt material are indispensable. .

Conventionally, as a rubber composition for improving the performance of a belt material, a hydrogenated rubber composed of an ethylenically unsaturated nitrile-conjugated diene copolymer is mixed with zinc methacrylate and an organic peroxide. It is known that the tensile strength is improved by this (Japanese Patent Laid-Open No.
31158). It is also known that a rubber composition is constituted by a solid rubber and an esterification product of a liquid diene polymer having a hydroxyl group at the terminal and an alkenyl succinic anhydride so that excellent tensile strength can be expressed (special characteristics (See Japanese Patent Publication No. 4-55453).

Further, as a rubber composition for extending the life of a belt material, when a general solid rubber is crosslinked with an organic peroxide, a sulfur component acts on the solid rubber as a co-crosslinking agent. However, it has been proposed that the bending fatigue resistance and the tear strength are improved to some extent (Japanese Patent Laid-Open No. Hei 5)
(See Japanese Patent Publication No. 339426). Further, a rubber composition has also been proposed in which polyfluorocarbon short fibers having a low coefficient of friction are added to solid rubber to reduce slip noise and vibration noise during belt running (JP-A-3-2).
65740).

[0005]

However, although the above-mentioned conventional rubber compositions are all excellent in tensile strength, they are not always satisfactory in physical properties such as bending fatigue characteristics and tear strength. Therefore, there is a problem that it is difficult to use it for a rubber product that is highly mechanically stimulated, for example, a power transmission belt for an automobile that requires high engine output.

The present invention has been made in view of the above points, and an object of the present invention is to add a resin which has been subjected to a special treatment to a solid rubber so that the entanglement between the resin and the rubber matrix is closely packed. Another object of the present invention is to provide a rubber composition having excellent bending fatigue characteristics and tear strength, and a transmission belt using the rubber composition.

[0007]

In order to achieve the above object, a first solution of the present invention is to add a fiber-forming fluororesin containing a polyfunctional co-crosslinking agent to a solid rubber to form a rubber. It is characterized in that it comprises a composition.

A second solution of the present invention is characterized in that, in the first solution, 0.05 to 2 parts by weight of a polyfunctional co-crosslinking agent is added to 1 part by weight of a fibrous fluororesin. And

A third solving means of the present invention is the first or second means.
At least a part of the belt-constituting rubber portion is constituted by the rubber composition according to the above-mentioned means.

The solid rubber used in the present invention is not particularly limited, and a commonly used synthetic rubber (S
R) and natural rubber (NR). Specific examples of such solid rubber include, for example, butadiene rubber (BR), isoprene rubber (IR), chloroprene rubber (CR), styrene-butadiene rubber (SBR), acrylonitrile-
Examples thereof include butadiene rubber (NBR) and hydrogenated products thereof, isobutylene-isoprene rubber (IIR), chlorosulfonated polyethylene rubber (CSM), etc. These may be used alone or in combination of two or more.

The fluororesin which can be used in the present invention is a fibrous fluororesin which is fibrous in the rubber due to the compressive force and the shearing force applied when it is kneaded with the above-mentioned solid rubber, and further entangled with each other and spread like a cobweb. A fluororesin that forms a network structure.

The fiber-forming fluororesin contains a polyfunctional co-crosslinking agent in advance. This polyfunctional co-crosslinking agent is a crosslinking agent for rubber, is usually used in combination with a peroxide crosslinking agent, and has two or more reactive functional groups in the molecular chain. For example, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, divinylbenzene, 2, bis (4-acryloxypolyethoxyphenyl) propane, tetraethylene glycol diacrylate, ethylene glycol dimethacrylate, magnesium methacrylate, zinc methacrylate, Examples thereof include triallyl trimellitate, calcium acrylate, triallyl isocyanurate, and the like, but are not limited to these as long as they are polyfunctional co-crosslinking agents that form a crosslinked structure in the vulcanization process. The form of this polyfunctional co-crosslinking agent is not limited to solid and liquid, and both can be used. However, the liquid polyfunctional co-crosslinking agent is easily dispersed by the fibrous fluororesin, and In addition, when kneading the fluororesin and the rubber, it also plays the role of a dispersion aid, which has an advantage that a more remarkable effect can be obtained.

The addition ratio of the fibrous fluororesin containing the polyfunctional co-crosslinking agent to the solid rubber is 100% by weight of the solid rubber, and the fibrogenic fluororesin containing the polyfunctional co-crosslinking agent. Is preferably set to 0.5 to 27 parts by weight, especially 1.0 to 8.0 parts by weight.
By using such an addition ratio, the fluororesin that has become fibrous due to the strong compressive force and shearing force during kneading of the rubber composition should be present in the rubber in a state of being spread like a cobweb. You can In addition, since the polyfunctional co-crosslinking agent can be present around each of the fibrous fluororesins and in the gaps, a crosslinked structure having a high crosslink density can be formed around the fluororesin. it can.
Thereby, the entanglement between the fibrous fluororesin and the rubber matrix and the mechanical binding force can be strengthened, and the separation of the fibrous fluororesin from the rubber due to mechanical stimulation can be reduced, and the obtained rubber Flexural fatigue characteristics and tear strength can be greatly improved.

The addition ratio of the above-mentioned polyfunctional co-crosslinking agent to the fibrous fluorocarbon resin cannot be unconditionally determined because it depends on the type of the polyfunctional co-crosslinking agent used and the like, but it can be made into fiber. 0.05 to 2 parts by weight of a polyfunctional co-crosslinking agent, based on 1 part by weight of the fluororesin.
It is desirable to set it to 2 to 1 part by weight. The range is set in such a range that when the amount of the polyfunctional co-crosslinking agent added is less than 0.05 parts by weight with respect to 1 part by weight of the fluororesin, the addition amount is too small and the above effects are sufficiently exerted. On the other hand, when the addition amount of the polyfunctional co-crosslinking agent exceeds 2 parts by weight with respect to 1 part by weight of the fluororesin, the polyfunctional co-crosslinking agent can be entirely absorbed in the fluororesin. However, when kneading with rubber, it produces the same effect as a co-crosslinking agent that is directly added to the rubber by mixing it with the rubber matrix. Therefore, the elastic modulus of the rubber becomes too high and the bending fatigue property tends to deteriorate. Because.

To add the polyfunctional co-crosslinking agent to the above-mentioned fibrous fluororesin, when the polyfunctional co-crosslinking agent is a liquid, the polyfunctional co-crosslinking agent is directly added to the fluororesin. , And mix evenly by stirring so that the polyfunctional co-crosslinking agent is absorbed by the fluororesin. On the other hand, when the polyfunctional co-crosslinking agent is solid, the polyfunctional co-crosslinking agent is 100 μm.
Grind into powder of m or less and mix with fluororesin. When using a liquid polyfunctional co-crosslinking agent,
Although not a necessary condition, it is desirable to add a dispersant such as molybdenum disulfide to the fluororesin, and by using the dispersant in this way, the fluororesin can be easily made into fibers. The amount of the dispersant added is not particularly limited, but 10 to 40 parts by weight is considered appropriate with respect to 100 parts by weight of the fluororesin.

In addition to the above components, various additives can be optionally added as required. Examples of such additives include crosslinking agents such as organic peroxides and zinc oxides, amines, amine-aldehyde reactants, amine-ketone reactants, antioxidants such as phenols; carbon black, white carbon, etc. Agents, fillers such as calcium carbonate, basic magnesium carbonate, diatomaceous earth, clay; tackifiers such as hydrogenated rosin, chroman-indene resin, polybutene; dioctyl adipate (DO
A), plasticizers such as dioctyl separate (DOS), dioctyl phthalate (DOP); process oils such as paraffin-based, naphthene-based, aromatic-based; kneading-type adhesion enhancers and the like used in ordinary rubber compositions Etc., etc., and conventionally used mechanical property improving agents such as unsaturated carboxylic acid metal salts can also be used in combination. Although ordinary staple fibers can be added to the rubber composition of the present invention, the rubber composition also has excellent bending fatigue characteristics in this case. Further, the amount of the above-mentioned additive added is not particularly limited, and it is desirable to appropriately adjust it according to the kind of additive used and the like.

The rubber composition of the present invention thus obtained exhibits excellent mechanical properties, in particular, excellent bending fatigue properties and tear strength, so that this rubber composition constitutes at least a part of the rubber portion constituting the belt. As a result, it is possible to obtain a transmission belt having characteristics such as high performance, long life, and high quietness. The rubber portion constituting the belt formed of this rubber composition varies depending on the type of the target transmission belt, but since the rubber composition of the present invention exhibits particularly excellent bending fatigue characteristics and tear strength, for example, a V-ribbed belt is used. Is preferably applied to the rib rubber layer, the tooth rubber layer of the toothed belt, the tooth cloth coating rubber, the lower rubber layer of the low edge belt, and the like.

An example of its application is shown in FIGS. FIG. 1 shows a toothed belt A. The toothed belt A comprises a back rubber layer 2 in which a plurality of core wires 1, 1, ... Made of glass fiber, aramid fiber, etc. are embedded, and the back rubber layer 2 has a plurality of teeth on its lower surface. The rubber layers 3, 3, ... Are arranged in a row in the longitudinal direction of the belt at a constant pitch.
A tooth cloth 4 made of nylon canvas is integrally attached to 3, .... The surface of the tooth cloth 4 is covered with coating rubber.

Each of the tooth rubber layers 3 is formed by using the rubber composition of the present invention as a rubber component. In each of the tooth rubber layers 3, the fluororesin capable of being formed into a fiber is in a cobweb shape. A network structure is formed, rubber is retained in such a network, and a highly cross-linked structure with a polyfunctional co-crosslinking agent is formed around the surface of the fibrous fluororesin and in the gaps. Since the interfacial destruction between the fluorinated resin and the rubber is less likely to occur, the mechanical properties of each tooth rubber layer 3 are improved, cracks are less likely to occur at the tooth root, and the life of each tooth rubber layer 3 is extended. There is.

In addition, the above-mentioned tooth rubber layers 3 and back rubber layers 2 usually use the same rubber component in many cases. Therefore, the rubber composition of the present invention is used not only for each tooth rubber layer 3 but also for the back rubber layers. It can also be used for layer 2.

FIG. 2 shows a V-ribbed belt B. The V-ribbed belt B includes an adhesive rubber layer 6 in which a plurality of core wires 5, 5, ... Made of polyester fiber, aramid fiber or the like are embedded, and the lower surface of the adhesive rubber layer 6 extends in the belt longitudinal direction. Three extending rib rubber layers 7, 7, 7 are formed, and an upper cloth 8 made of rubberized canvas is integrally attached to the upper surface of the adhesive rubber layer 7.

Each rib rubber layer 7 is formed by using the rubber composition of the present invention as a rubber component, and each rib rubber layer 7 has the same fiber as each tooth rubber layer 3 of the toothed belt A. The fluorocarbon resin forms a cobweb-like network structure, and the polyfunctional co-crosslinking agent provides a highly cross-linked structure around the fibrous fluorocarbon resin to strengthen the bond between the fluorocarbon resin and the rubber. Therefore, the mechanical properties of each rib rubber layer 7 are improved, cracks are less likely to occur, and the life of each rib rubber layer 7 is extended.

As described above, the transmission belt (toothed belt A, V-ribbed belt B) in which at least a part of the belt-constituting rubber portion (the tooth rubber layer 3 and the rib rubber layer 7) is formed by the rubber composition of the present invention, In particular, mechanical properties such as flexural fatigue resistance, friction coefficient, and tear strength are improved, high performance and long life are realized, and quietness is also excellent.

The transmission belt of the present invention has been described above with reference to FIGS. 1 and 2, but the present invention is not limited to the embodiment shown in the drawings.

[0025]

With the above-mentioned structure, in the first to third means of the present invention, when the rubber composition is kneaded, the fiberizable fluororesin containing the polyfunctional co-crosslinking agent is treated by a strong shearing force. The fibrous fluororesin is entangled with each other to form a cobweb-like network structure, and the solid rubber is held in the cobweb-like net of the fibrous fluororesin.

When the rubber is crosslinked by vulcanization,
The fluororesin spreads like a cobweb in the rubber, and crosslinking is also performed by the polyfunctional co-crosslinking agent existing around and in the gaps between the individual fibrous fluororesins. For this reason,
A crosslinked structure having a high crosslink density is formed around the fluororesin in the form of a cobweb, the entanglement between the fibrous fluororesin and the rubber matrix and the mechanical binding force are strengthened, and the fibrous fluororesin is mechanically stimulated. The situation that the rubber is separated from the rubber is reduced. Therefore, the bending fatigue property and tear strength of the obtained rubber are significantly improved.

[0027]

EXAMPLES Next, the present invention will be described in more detail based on examples, but the present invention is not limited to such examples.

(Examples 1 to 7 and Comparative Examples 1 to 3) Hydrogenated NBR was used as the solid rubber, and the polyfunctional copolymer was used in Examples 1 to 7 in proportion to the co-crosslinking agent / PTFE shown in Table 1. A fibrinizable fluororesin mixture containing a crosslinking agent was prepared (however, Comparative Examples 1 to 3 do not use this fluororesin mixture), and the amount of the fluororesin added was 5/100 parts by weight based on the hydrogenated NBR. Add it in proportion, and also
2 parts by weight of an antioxidant, 1 part by weight of stearic acid, 10 parts by weight of zinc oxide, 20 parts by weight of carbon black and 2 parts by weight of peroxide were added to 100 parts by weight of solid rubber, and Example 7 and Comparative Example 3 were further added. For, the nylon fibers were added in the amounts shown in Table 1 and kneaded with a Banbury mixer for about 5 minutes to obtain a rubber composition.

Here, the hydrogenated NBR is hydrogenated acrylonitrile-butadiene rubber (manufactured by Nippon Zeon Co., Ltd.).
2-Mercaptubenzimidazole manufactured by Ouchi Shinko Chemical Co., Ltd. as an anti-aging agent, FEF (N550) as carbon black, and trimethylol manufactured by Sanshin Chemical Co., Ltd. as a co-crosslinking agent. Propane trimethacrylate is used for the fibrous fluororesin, Teflon K manufactured by Mitsui DuPont Fluorochemical Co., Ltd., and nylon fiber is nylon short fiber with a fiber length of 0.6 mm and a fineness of 2 denier. I was there.

Next, the obtained rubber composition was rolled with an open roll to give an unvulcanized rubber sheet, and this unvulcanized rubber sheet was press-vulcanized at 160 ° C. for 30 minutes to obtain a vulcanized rubber sheet. The physical properties of the obtained vulcanized rubber sheet were examined for tear strength and flexural fatigue properties according to the following methods. Table 1 shows the results.

<Tear strength> B of JIS K 6301
According to the method, the test was conducted at 25 ° C. to measure the tear strength (kN / m).

<Bending Fatigue Properties> In accordance with JIS K 6301, a crack growth test was conducted at a stroke of 19 to 75 mm and 120 ° C. using a DeMatcher bending fatigue tester, and the number of bendings when the crack length became 20 mm was determined. The fatigue characteristics are shown.

<Life of Tooth Rubber Layer> The rubber compositions obtained in Examples 1 to 6 and the rubber compositions obtained in Comparative Examples 1 and 2 were used in the tooth rubber layer 3 and the back rubber layer 2, respectively. Toothed belt A (number of teeth is 92, tooth profile is ZB (JASO E105-81 (automotive belt) and E106-81 (pulley) standard), width 19 m
m) was produced.

The toothed belt A thus obtained was subjected to a triaxial running test using a triaxial running test apparatus shown in FIG.
In FIG. 3, the drive pulley 9 is a toothed pulley 20ZB (JASO
E105-81, E106-81), the load driven pulley 10 is a toothed pulley 40ZB, and the drive pulley 9 is at an arrow C at 6000 rpm.
The toothed belt A was rotated in the direction of 1, and the initial tension of the toothed belt A was set to 15 kgf by the idler pulley 11, and the belt was run in the direction of arrow D1 with 10 horsepower. In this case, the environmental temperature is 130 ° C. Then, the time until the tooth rubber layer 3 of the toothed belt A was damaged was measured, and the average value of each of the nine toothed belts A was calculated. The results are also shown in Table 1.

Further, the V-ribbed belt B shown in FIG. 2 was manufactured using the rubber compositions obtained in Example 7 and Comparative Example 3, and the life of the rib rubber layer 7 was examined according to the following method.

<Life of Rib Rubber Layer> The rubber compositions obtained in Example 7 and Comparative Example 3 were used in the rib rubber layer 7, and the V-ribbed belt B (number of ribs 3, length 975 cm) shown in FIG. 2 was used.
Was manufactured.

The obtained V-ribbed belt B is shown in FIG.
A three-axis running test was performed using the three-axis running test device shown in FIG. In FIG. 4, the drive pulley 12 has a diameter of 120 mm,
The driven pulley 13 has a diameter of 120 mm and a diameter of 45 mm.
The tension of the V-ribbed belt B is adjusted by the idler pulley 14 of mm. Load 12 horsepower of driven pulley 13, set weight (tension) on idler pulley 14
Under the conditions of 85 kgf and the rotation speed of the drive pulley 12 of 4900 rpm, the drive pulley 12 was rotated in the direction of arrow C2 and the V-ribbed belt B was run in the direction of arrow D2 in an atmosphere of 85 ° C. At this time, the time taken for a crack generated at the tip of the rib rubber layer 7 to reach the core wire 5 was measured.

[0038]

[Table 1]

From the results shown in Table 1, each of the rubbers made of the rubber compositions obtained in Examples 1 to 6 has a tear strength higher than that of the rubber made of the rubber composition obtained in Comparative Example 1. It can be seen that they are equal to or more than that, have extremely excellent bending fatigue characteristics, and have a long life when used as the tooth rubber layer 3 of the toothed belt A. Further, when the amount of the crosslinking agent added exceeds 2/1 with respect to PTFE, an excessive amount of the co-crosslinking agent is directly dispersed in the rubber, the elastic modulus becomes too high, and the bending fatigue characteristic and the tearing characteristic deteriorate. As compared with Example 7 and Comparative Example 3, it is found that the addition of the co-crosslinking agent in the short fiber addition system is effective in improving the bending fatigue property and the tear property, and the life of the rib rubber layer 7 is extended.

Further, comparing Example 3 with Comparative Example 2, when the co-crosslinking agent was directly added to the rubber, no improvement in mechanical properties was observed, while in Example 3, the co-crosslinking agent was made into fiber. When it is added to a possible fluororesin to prepare a mixture and the mixture is further dispersed in rubber, the tear strength and bending fatigue properties are significantly improved, and when it is used as the tooth rubber layer 3 of the toothed belt A, it has a long life. It has reached the end of its life.

[0041]

As described above, according to the present invention according to claims 1 to 3, a fibrizable fluororesin containing a polyfunctional co-crosslinking agent is added to a solid rubber to form a rubber composition. Since it is composed, it exhibits very excellent flexural fatigue properties and tear strength due to the fibrous fluororesin that spread like a cobweb in the rubber and the polyfunctional co-crosslinking agent that exists around and in the gaps between the fibrous fluororesins. A rubber composition that can be obtained can be obtained. Further, by forming at least a part of the belt-constituting rubber portion with this rubber composition, it is possible to obtain a transmission belt having further excellent high performance and long life.

[Brief description of drawings]

FIG. 1 is a perspective view partially showing a toothed belt.

FIG. 2 is a perspective view partially showing a V-ribbed belt.

FIG. 3 is a schematic configuration diagram of a test device used for a triaxial running test of a toothed belt.

FIG. 4 is a schematic configuration diagram of a test device used for a triaxial running test of a V-ribbed belt.

[Explanation of symbols]

 3 Tooth rubber layer (at least a part of the rubber portion of the belt) 7 Rib rubber layer (at least a part of the rubber portion of the belt) A Toothed belt (transmission belt) B V Ribbed belt (transmission belt)

Claims (3)

[Claims] 1. A rubber composition comprising a solid rubber to which a fibrinizable fluororesin containing a polyfunctional co-crosslinking agent is added. 2. The rubber composition according to claim 1, wherein 0.05 to 2 parts by weight of a polyfunctional co-crosslinking agent is added to 1 part by weight of the fibrous fluororesin. 3. A transmission belt comprising the rubber composition according to claim 1 or 2, wherein at least a part of a rubber portion constituting the belt is formed.