JP2002115746A - Toothed belt - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve an adhesion between a core wire and an adhesive rubber by a toothed belt using a hydrogenated nitrile rubber and to enhance a durability and a heat resistant property of the belt. SOLUTION: In the belt 1 with tooth using a hydrogenated nitrile rubber, a sulfur vulcanization type hydrogenated nitrile rubber is used as an adhesive rubber layer 3 in which a core wire 4 of the belt 1 is buried and an organic peroxide vulcanization type hydrogenated nitrile rubber is used as a back rubber layer 2. Any sulfur vulcanization and organic peroxide type hydrogenated nitrile rubber may be used as a tooth rubber layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toothed belt (timing belt), and more particularly to a toothed belt having excellent durability using hydrogenated nitrile rubber as a raw material rubber.

[0002]

2. Description of the Related Art A conventional toothed belt is composed of a rubber compound using chloroprene as a raw rubber, a tooth rubber and a backing rubber, and a glass fiber cord bonded with a resorcinol-formalin latex (RFL) solution to a core wire. It is composed of a tooth cloth (teeth cloth) in which the belt is used in the longitudinal direction of the belt with a crimped nylon or the like as a weft. In recent years, due to social demands for energy saving and compactness, the atmosphere around the engine room of an automobile has been increased. The temperature is rising compared to the past.

That is, the OHC-driven (overhead cam-driven) toothed belt for automobiles is used at a high ambient temperature due to the downsizing of the engine room and the like. The belt was easily cut due to a phenomenon from cracks at the base to chipping, or deterioration of the glass core wire due to bending at a high temperature.

[0004] In recent years, in particular, in response to the demand for longer life of automobile toothed belts, hydrogenated nitrile rubber (HNBR) obtained by hydrogenating chloroprene, chlorosulfonated polyethylene (CSM) or acrylonitrile-butadiene copolymer has been developed. ) Has been used as a raw rubber for rubber compounds. (Refer to Japanese Patent Application Laid-Open No. 62-159827)

[0005] However, since rubber is required to have dynamic resistance to fatigue in addition to oil resistance and heat resistance, rubber compositions mostly sulfur-vulcanized are used. In the case of sulfur vulcanization, it is common to use a thiuram-based, thiazole-based, sulfenamide-based vulcanization accelerator alone or in combination with sulfur.

[0006]

However, in this vulcanization system, it is known that the amount of sulfur greatly affects the heat resistance and also greatly affects the dynamic properties. That is, although the heat resistance is improved by reducing the amount of sulfur, dynamic strain,
Dynamic characteristics such as heat generation are deteriorated. Conversely, when the amount of sulfur is increased, the dynamic characteristics are improved, but the heat resistance is extremely deteriorated. Therefore, in consideration of the dynamic performance of the belt, a sulfur supplier containing at least 0.2 parts by weight of sulfur is required, and preferably 0.5 parts by weight or more, based on 100 parts by weight of the hydrogenated nitrile rubber. It was necessary. Therefore, in this sulfur-vulcanized rubber composition of the hydrogenated nitrile rubber, although there is a slight difference depending on the combination with the antioxidant, depending on the iodine value of the hydrogenated nitrile rubber and the amount of the sulfur donor added. Naturally, there was a limit to improving heat resistance.

Therefore, recently, belts using an organic peroxide vulcanization system have been developed in order to adapt to even higher loads. However, organic peroxide vulcanization does not
There is a problem of curing L. On the other hand, those using the sulfur vulcanization system as described above have a problem that the belt performance, especially the heat resistance, is inferior to the organic peroxide vulcanization, and the running life is remarkably reduced.

The present invention has been made in view of the above situation, and in order to cope with the situation, in the case of a toothed belt using a hydrogenated nitrile rubber, in particular, by examining the length of the double vulcanizing system on the belt performance, It is an object of the present invention to provide a toothed belt having a long running life by improving the adhesive force between a core wire and an adhesive rubber and improving the durability and heat resistance of the belt.

[0009]

That is, according to the present invention, which meets the above object, a tooth rubber layer having a tooth cloth laminated on an outer surface thereof is provided below an adhesive rubber layer in which a cord is embedded along the longitudinal direction of the belt. In a toothed belt using hydrogenated nitrile rubber for each rubber layer where a back rubber layer is provided on the adhesive rubber layer,
It is characterized in that sulfur-vulcanized hydrogenated nitrile rubber is used as the adhesive rubber layer and organic peroxide-cured hydrogenated nitrile is used as the backing rubber layer. It is to be noted that either a sulfur vulcanization type or an organic peroxide vulcanization type hydrogenated nitrile rubber can be used for the tooth rubber layer.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows an example of a toothed belt according to the present invention. The toothed belt 1 of the present invention is made of a low-stretch, high-strength rope such as a glass fiber cord or an aramid cord along the longitudinal direction of the belt. A tooth rubber layer 6 in which a tooth cloth 5 is laminated on the outer surface is disposed below the adhesive rubber layer 3 in which the core wire 4 is embedded, and a back rubber layer 2 is disposed above the adhesive rubber layer 3. Have been.

Here, the toothed belt 1 uses hydrogenated nitrile rubber (H-NBR) as a raw material rubber for the adhesive rubber layer 3, the tooth rubber layer 6, and the back rubber layer 2;
A knitted and woven fabric is used in which a known fiber such as nylon or aramid fiber is used as a filament or spun yarn and knitted appropriately. In particular, the use of hydrogenated nitrile rubber for the back rubber 2, the adhesive rubber layer 3, and the tooth rubber layer 6 is a basic configuration of the present invention. The hydrogenated nitrile rubber used for this raw rubber has a hydrogenation ratio of 80% or more, and particularly has heat resistance,
In order to exhibit the ozone resistance, 90% or more is preferable. Hydrogenated nitrile rubber having a hydrogenation rate of less than 80% is not preferred because heat resistance and ozone resistance are extremely reduced.
In consideration of heat resistance, the iodine value is preferably from 5 to 35, and from the viewpoint of oil resistance and cold resistance, the amount of bound acrylonitrile is preferably in the range of 20 to 40%.

Thus, in the present invention, the use of a hydrogenated nitrile rubber as described above is the basic structure.
In particular, as the hydrogenated nitrile rubber in each layer, a sulfur vulcanized hydrogenated nitrile rubber is used for the rubber of the adhesive rubber layer 3,
It is an important feature that an organic peroxide vulcanized hydrogenated nitrile rubber is used for the rubber of the back rubber layer 2.

The adhesive rubber layer 3 is a sulfur-vulcanized hydrogenated nitrile rubber, which is obtained by blending sulfur, a sulfur-containing sulfur donor and a vulcanization accelerator with the hydrogenated nitrile rubber. Examples of the sulfur donor include tetramethylthiuram monosulfide (TMTM), tetramethylthiuram disulfide (TMTD), tetrakis (2-ethylhexyl) thiuram sulfide (TOT-N), and a vulcanization accelerator. Are benzothiazoles such as dithiocarbamate vulcanization accelerators such as zinc benzyldithiocarbamate, 2-mercaptobenzothiazole, dibenzothiazyl sulfide, zinc salt of 2-mercaptobenzothiazole and cyclohexylamine salt of 2-mercaptobenzothiazole Vulcanization accelerator, N
Sulfenamide-based vulcanization accelerators such as -cyclohexyl-2-benzothiazylsulfenamide, N-tert-butyl-2benzothiazylphenamide and N, N-dicyclohexyl-2-benzothiazylsulfenamide. Can be mentioned.

Among the above, the combination of tetrakis (2-ethylhexyl) thiuram sulfide with a dithiocarbamate-based vulcanization accelerator can suppress the generation of nitrosamine during vulcanization of rubber, so that belt production can be suppressed. In such a work environment, there is an advantage that harm to the worker can be reduced. Specifically, 0.1 to 10 parts by weight of tetrakis (2-ethylhexyl) thiuram sulfide and 0.1 to 10 parts by weight of a dithiocarbamate-based vulcanization accelerator are added to 100 parts by weight of the hydrogenated nitrile rubber. Mix. Further, if necessary, various agents such as reinforcing agents such as carbon black and silica, fillers such as clay and calcium carbonate, softeners, processing aids, and antioxidants may be added.

On the other hand, the organic peroxide vulcanized rubber of the back rubber 2 contains peroxide as a vulcanizing agent. Also, TAIC, TAC, 1,2 polybutadiene as a co-crosslinking agent,
Metal salts of unsaturated carboxylic acids, oximes, guanidine,
Those usually used for peroxide crosslinking, such as trimethylolpropane trimethacrylate, ethylene glycol dimethacrylate, NN'-m-phenylenebismaleimide, and sulfur, can also be used.

Of these, TAIC or TAC is preferable, and the addition thereof increases the degree of cross-linking and can prevent adhesive wear and the like. The addition amount of TAIC or TAC is 0.2 to 10 parts by weight based on 100 parts by weight of the above-mentioned hydrogenated nitrile rubber. The effect of improving the abrasion is small. On the other hand, if it exceeds 10 parts by weight, the elongation of the vulcanized rubber is remarkably reduced, which causes a problem in bending resistance.

Further, by adding 0.01 to 1 part by weight of sulfur to 100 parts by weight of the hydrogenated nitrile rubber to the back rubber layer 2, it is possible to suppress a decrease in the elongation of the vulcanized rubber. . If the amount exceeds 1 part by weight, the degree of crosslinking is not improved as expected, so that the non-wear resistance and adhesive wear resistance of the vulcanized rubber are not improved.

The organic peroxide is usually
Rubber, diacyl peroxide, paoxy ester, diallyl peroxide, di-t-butyl peroxide, t-butyl cumyl peroxide, dicumyl peroxide, 2.5-dimethyl-2. 5-di (t-butylperoxy) -hexane-
3,1,3-bis (t-butylperoxy-isopropyl) benzene, 1.1-di-butylperoxy-3,
There are 3,5-trimethylcyclohexane and the like, and those having a one-minute half-life of 150 to 250 ° C by thermal decomposition are preferable. The addition amount is about 1 to 8 parts by weight, preferably 2.0 parts by weight, based on 100 parts by weight of the hydrogenated nitrile rubber.

The present invention relates to a sulfur-vulcanized system of the above hydrogenated hydrogenated nitrile rubber, that is, a sulfur-vulcanized vulcanizate is used as an adhesive rubber layer 3, and an organic peroxide of the hydrogenated nitrile rubber is also used. An oxide vulcanization system, that is, a crosslinked product obtained by organic peroxide vulcanization is used as the back rubber layer 2, and the above-mentioned sulfur vulcanization system or organic peroxide vulcanization system is used for the tooth rubber layer 6. Any of the above is used. It should be noted that short fibers made of nylon, polyester, cotton, aramid, or the like can be appropriately mixed into the tooth rubber layer 6. Usually, the addition amount is 1 to 30 parts by weight based on 100 parts by weight of the hydrogenated nitrile rubber.
Parts by weight. Further, the tooth rubber layer 6 is composed of 1 to 50 parts by weight, preferably 1 to 50 parts by weight of fine short fiber rubber in which fine short fibers having a fiber diameter of 1.0 μm or less are combined with 100 parts by weight of hydrogenated nitrile rubber as a matrix rubber. May be contained in an amount of 5 to 25 parts by weight.

[0021] The short microfiber-reinforced rubber has a rubber component as a continuous phase in which the short microfibers are dispersed in a fine form, and the short microfibers form a strong chemical bond or interaction with the rubber component at the interface. ing. For this reason, the rubber layer containing this hardly cracks, and even if the cracks do not easily propagate. In addition, the belt using this also has excellent heat resistance, cold resistance, bending resistance, and abrasion resistance. Further, the tooth rubber layer 6 may include a reinforcing agent such as carbon black and silica, a filler such as clay and calcium carbonate, a softener, a processing aid, an antioxidant, and a co-crosslinking agent such as TAIC, if necessary. Various drugs may be added.

On the other hand, the core wire 4 of the belt embedded in the adhesive rubber layer 3 is, as described above, a polyethylene terephthalate fiber and a polyester fiber mainly composed of ethylene-2,6-naphthalate. A rope made of an aliphatic or aromatic polyamide fiber is used, and is subjected to an adhesive treatment for the purpose of improving adhesiveness to rubber. As such an adhesive treatment, the fiber is resorcinol-formalin-
Generally, after immersion in latex (RFL solution), the adhesive layer is uniformly formed on the surface by heating and drying. However, without being limited to this, there is a method of performing a pretreatment with an epoxy or isocyanate compound and then treating with an RFL solution.

The RFL solution is obtained by mixing a latex with an initial condensate of resorcinol and formalin. The latex used here is a polymer such as chloroprene, styrene / butadiene / vinylpyridine, and a polymer, hydrogenated nitrile, NBR, etc. However, hydrogenated nitrile rubber is preferred from the constituent materials of the adhesive rubber layer and the back rubber layer.

Next, the tooth cloth 5 laminated on the surface of the tooth rubber layer 6
Is a cloth woven or knitted in a plain weave, a twill weave, a satin weave, or the like using a yarn made of cotton, polyamide, polyethylene terephthalate, or aramid fiber. These are then
Adhesion treatment is performed by FL treatment to increase the thickness, and wrinkling of the tubular belt canvas is prevented from occurring in the spinning process. RFL treatment is performed by immersing in RFL solution for 0.1 to 20 seconds,
Dry at 200 ° C. for 30-600 seconds.

The RFL solution used in the RFL treatment is a mixture of a resorcinol and formalin initial condensate and a rubber latex, as in the case of the above-mentioned core wire. In this case, the molar ratio of resorcinol to formalin is 1: 0. 0.5-3
Is preferable for increasing the adhesive strength. In addition, the initial condensate of resorcinol and formalin has a resin content of 10 to 1 based on 100 parts by weight of the rubber content of the latex.
After mixing with latex so as to be 00 parts by weight, the total solid concentration is adjusted to be 5 to 40%. In addition,
In some cases, a carbon black liquid is appropriately mixed with the RFL liquid to blacken the treated material. In the case of a cotton fabric, a known surfactant may be added to the RFL solution in an amount of 0.1 to 13.0% by weight.

The latex is styrene-butadiene-
Hynylbiridine ternary polymer, latex of chlorosulfonated polyethylene, hydrogenated nitrile rubber, shrimp chlorohydrin, natural rubber, SBR, chloroprene rubber, olefin-vinyl ester copolymer, etc. Hydrogenated nitrile rubber is preferred in relation to the constituent materials of the backing rubber layer.

[0027]

Embodiments of the present invention will be described below. First, according to the following Table 1, respective formulations of a sulfur vulcanization system (S vulcanization) and an organic peroxide vulcanization system (PO vulcanization) of hydrogenated nitrile rubber were prepared. In the table, DCP (40%) is a vulcanizing agent (peroxide) containing 40% of dicumyl peroxide, and 60% of calcium carbonate etc.
Included.

[0028]

[Table 1]

After winding the canvas around the mold,
The tooth rubber layer, the lower adhesive rubber layer, the core wire, the upper adhesive rubber layer and the back rubber layer are sequentially wound, heated and pressed to obtain a vulcanized belt sleeve, and the back rubber layer side is polished to a predetermined thickness. The hydrogenated nitrile rubber is obtained by burying a cord made of a glass fiber rope as shown in FIG. 1 in an adhesive rubber layer made of a hydrogenated nitrile rubber composition, and laminating a rubberized canvas underneath. A tooth rubber layer composed of the composition,
On the other hand, a belt having a back rubber layer made of the same composition on the upper side of the adhesive rubber layer was produced.

Using the vulcanization systems shown in Table 1 above, various vulcanization systems for the adhesive rubber, the back rubber and the tooth rubber were obtained at 23.degree. C. and 140.degree. The belts of the example and the comparative example were produced, respectively.
Stripping was performed at a speed of mm / min, and a core wire pull-out test was performed to compare the adhesive force per two cores. The results were as shown in Table 2 below.

[0031]

[Table 2]

From Table 2 above, it can be seen that high adhesion was obtained in both Examples and Comparative Examples 3 and 4 in which a sulfur vulcanization system was used for the adhesive rubber layer. Those who use are clearly in decline.

Next, the belts of the above Examples and Comparative Examples were subjected to a 120 ° C. heat resistant running test in the layout shown in FIG. Pulley: Dr 21 teeth, Dn 42 teeth, Tenφ52 (flat pulley) Drive pulley rotation speed: 7200 rpm. Load: 3.67 KW Initial tension: 147 N The obtained results were as shown in Table 3 below.

[0034]

[Table 3]

From Table 3 above, in Comparative Examples 1 and 2, the peroxide life was used for the adhesive rubber, so that the belt life was significantly shortened due to the hardening of the core wire. On the other hand, Comparative Examples 3 and 4
Because the sulfur vulcanization system is used for the back rubber, the rubber is thermally aged and has a long life. On the other hand, in Examples 1 and 2 according to the present invention, the core wire was not deteriorated by the peroxide, and it was found that the back rubber portion had good heat resistance due to peroxide vulcanization.

[0036]

As described above, the toothed belt of the present invention uses a sulfur vulcanizing system as a vulcanizing system for the adhesive rubber layer in which the core of the belt is embedded, and an organic peroxide vulcanizing system for the backing rubber layer. Since the adhesive rubber layer in which the core wire is buried uses the sulfur vulcanization system, the RFL of the core wire is not cured, so that the adhesive strength between the core wire and the adhesive rubber is reduced. , While not shortening the belt life due to hardening of the core wire,
On the other hand, since the back rubber layer is an organic peroxide vulcanized effective for heat resistance, it has an effect of securing good heat resistance and adapting to recent high loads, and is used as a toothed belt. Practicality can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of a toothed belt according to the present invention, a part of which is shown in cross section.

FIG. 2 is a diagram showing a layout of a heat resistant running test of a belt.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 toothed belt 2 back rubber layer 3 adhesive rubber layer 4 core wire 5 tooth cloth 6 tooth rubber layer

Claims (2)

[Claims] 1. A tooth rubber layer in which a tooth cloth is laminated on an outer surface is disposed below an adhesive rubber layer in which a cord is embedded along a longitudinal direction of the belt, and a back rubber layer is disposed above the adhesive rubber layer. In a toothed belt using hydrogenated nitrile rubber for each rubber layer,
A toothed belt, wherein a sulfur vulcanized hydrogenated nitrile rubber is used as the adhesive rubber layer, and an organic peroxide vulcanized hydrogenated nitrile is used as the back rubber layer. 2. The toothed belt according to claim 1, wherein a sulfur vulcanized or organic peroxide vulcanized hydrogenated nitrile rubber is used as the tooth rubber layer.