JPS6146697B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a power transmission belt, and more particularly to a power transmission belt that has excellent durability at high temperatures. Transmission belts are widely used industrially, but
In recent years, there have been an increasing number of applications that require durability at high temperatures. For example, belts used in close proximity to automobile engines are required to have sufficient durability even at temperatures of around 120°C, but conventional belts quickly deteriorate and break when used at such high temperatures. There's a problem. The present invention was made in order to provide a power transmission belt that has sufficient durability even under such high temperatures. Generally, power transmission belts consist of a fiber layer to provide strength and an elastic layer to hold this, but in order for the belt to have durability at high temperatures,
It is required that the elastic layer has excellent heat resistance. Non-sulfur-modified chloroprene rubber does not contain sulfur in its polymer main chain and has excellent heat resistance and compressive strength, so it has traditionally been used favorably in rubber products that are used at high temperatures. It has the disadvantage of poor adhesion. In order to improve these drawbacks of chloroprene rubber, it has been proposed to incorporate various additives, but the addition of additives not only impairs the storage stability of unvulcanized rubber, but also causes problems when vulcanized. On the contrary, it often impairs the heat resistance and compressive strength, which were the advantages of non-sulfur modified types. For example, it is generally known that sulfur or hydrated silica is added to improve the adhesion of rubber, but when this method is applied to chloroprene rubber, the heat resistance and compression fatigue resistance of vulcanized rubber are significantly deteriorated. Furthermore, according to the method of adding melamines and resorcinol, the storage stability of unvulcanized rubber is significantly impaired. For this reason, in power transmission belts, methods such as providing an adhesive rubber layer between the fiber layer and the elastic layer to improve adhesion are generally adopted. If the heat resistance of the holding rubber layer is poor, in the case of power transmission belts used under high temperature conditions, the adhesive rubber layer may deteriorate, accelerating fatigue of the fiber layer, or cracking may occur in the holding rubber layer. , does not have durability at high temperatures. The present invention was made to solve the various problems described above, and an object of the present invention is to provide a power transmission belt with excellent durability at high temperatures. The power transmission belt according to the present invention is a power transmission belt consisting of a fiber layer and an elastic layer, in which the elastic layer contains (a) 100 parts by weight of rubber containing 50% by weight or more of non-sulfur-modified chloroprene rubber, and (b) general rubber. formula (However, R ¹ is each independently an alkyl group,
It represents a nitrogen-containing carbon ring formed by an aryl group or two R ¹ together with nitrogen, and x represents an integer of 1 to 6. ) 2 to 15 parts by weight of a thiuram compound represented by (c) general formula (However, R ² is each independently an alkyl group,
Aryl group, cycloalkyl group or two ^R2
indicates a nitrogen-containing carbon ring formed with nitrogen. ) and the general formula (However, R ³ represents an alkyl group.) It is characterized by being made of a vulcanized rubber of a rubber composition containing 0.3 to 5 parts by weight of at least one nickel salt selected from nickel xanthate represented by . The thiuram compound used in the present invention is represented by the above general formula, where R ¹ is preferably an alkyl group having 5 or less carbon atoms, an aryl group having 8 or less carbon atoms, or two R ^1s formed together with nitrogen. represents a nitrogen-containing carbon ring having 10 or less carbon atoms, and x represents an integer of 1 to 4. Therefore, preferred specific examples include tetramethylthiuram monosulfide, tetramethylthiuram disulfide, tetraethylthiuram disulfide, dipentamethylenethiuram tetrasulfide, and the like. Such thiuram compounds are rubber containing 50% by weight or more of non-sulfur modified chloroprene rubber.
For every 100 parts by weight, 2 to 15 parts by weight, preferably 4 to 10 parts by weight are used. Generally, in the case of sulfur-modified chloroprene rubber, a small amount of thiuram compounds may be added as a stabilizer during the production of the raw material polymer, but blending a large amount of thiuram compounds as described above
This is limited to sulfur-free vulcanization of natural rubber, styrene-butadiene, etc., and has not been applied to chloroprene rubber. The reason for this is that thiuram compounds act as vulcanization retardants for chloroprene rubber, so their use is limited to the sole purpose of preventing scorch. This is because the hardness and modulus of the vulcanized rubber decrease, which not only deteriorates the compression properties but also causes severe blooming. However, in the present invention, a large amount of the thiuram compound is 0.3 to 5 parts by weight, preferably 0.5 to 2 parts by weight of nickel dithiocarbamate represented by the general formula () per 100 parts by weight of rubber mainly composed of chloroprene rubber. And/or by using nickel xanthate represented by the general formula (), it was possible to improve the adhesiveness of chloroprene rubber while effectively preventing blooming of chloroprene rubber caused by the addition of a large amount of a thiuram compound. In the nickel dithiocarbamate represented by the general formula (), R ² preferably represents an aryl group or arylalkyl group having 8 or less carbon atoms, or a nitrogen-containing carbon ring formed by bonding two R ² together with nitrogen, Preferred specific examples include nickel dimethyldithiocarbamate, nickel diethyldithiocarbamate, nickel di-n-butyldithiocarbamate, nickel pentamethylenedithiocarbamate, nickel cyclohexylethyldithiocarbamate, nickel dipendyldithiocarbamate, nickel lupetidine dithiocarbamate, and nickel dithiocarbamate. Examples include nickel pethidine dithiocarbamate and nickel ethyl phenyl dithiocarbamate. Further, in the nickel xanthate represented by the general formula (), R ³ is preferably an alkyl group having 2 to 5 carbon atoms, and specific examples include isopropyl nickel xanthate, butyl nickel xanthate, and ethyl nickel xanthate. etc. can be mentioned. Furthermore, in the present invention, in order to improve the compression properties of the vulcanized chloroprene rubber, thiourea-based vulcanization accelerators such as thiocarboanilide, diorthotolylthiourea, ethylenethiourea, and diethylthiourea, diphenylguanidine, and diorthotolylthiourea are used as vulcanization accelerators. It is desirable to use at least one guanidine type such as tolylguanidine and diphenylguanidine phthalate in combination, and in this case, the appropriate amount is 1 to 5 parts by weight per 100 parts by weight of rubber mainly composed of chloroprene rubber. The rubber composition used in the present invention may contain 50% by weight or more of non-sulfur-modified chloroprene rubber, and the remainder may be, for example, sulfur-modified chloroprene rubber, polybutadiene, styrene-butadiene rubber, epichlorohydrin rubber, or the like.
It goes without saying that it may also contain other compounding agents such as reinforcing agents, fillers, plasticizers, anti-aging agents, vulcanization aids, activators, etc. for ordinary chloroprene rubber. The fiber layer used in the belt of the present invention is, for example, organic fiber such as polyamide fiber, polyaramid fiber, polyester fiber, vinylon fiber, rayon, or cotton, or inorganic fiber such as carbon fiber, glass fiber, steel fiber, or ceramic fiber. However, it is not limited to these. It is desirable that such fibers be subjected to a commonly used treatment for the purpose of improving adhesion to rubber. A common method for such fiber treatment is to immerse the fibers in resorcinol-formalin latex (RFL liquid) and heat and dry it to form an adhesive layer uniformly on the surface. Stabilized isocyanate compounds or epoxy compounds may be incorporated, or RFL treatment and treatment with such active compounds may be used in combination. A belt using the chloroprene rubber composition as described above can be manufactured by a conventionally known method. As described above, in the present invention, by using a large amount of thiuram compound exceeding the usual range for non-sulfur modified chloroprene rubber in combination with nickel dithiocarbamate and/or nickel xanthate, the excellent advantages of chloroprene rubber are achieved. It is possible to obtain an adhesive chloroprene rubber composition that suppresses blooming and has excellent storage stability while maintaining heat resistance and compression fatigue resistance,
Therefore, a power transmission belt using the vulcanized rubber of this rubber composition for at least one of the holding rubber layer and the adhesive rubber layer has not only excellent adhesion to fibers but also excellent heat resistance. It has outstanding durability at high temperatures. Reference examples and examples of the present invention are listed below,
The present invention is not limited in any way by these Examples. Reference example (fiber treatment) An aqueous solution consisting of 400 g of water, 19.7 g of resorcinol, and 29.3 g of 37% formalin was mixed with caustic soda to pH 10.
and aged at 25°C for 6 hours. Next, this liquid
400g, 240g of vinylpyridine-SBR latex (JSR 0650 manufactured by Japan Synthetic Rubber Co., Ltd.), 120g of SBR latex (JSR 0691 manufactured by Japan Synthetic Rubber Co., Ltd.) and 90g of water.
were mixed and aged at 25°C for 6 hours to prepare an RFL solution. Add this RFL liquid to nylon 6 cord (210/3
x9 configuration) was immersed, and then heat-treated at 210°C for 2 minutes. Polyester cord (1100D/3x3 configuration)
was immersed in a trichlene solution of diphenylmethane diisocyanate, heated at 220°C for 1 minute, and then subjected to RFL treatment in the same manner as above. Polyaramid cord (1500D/1×5 configuration)
is a mixture consisting of 2.22 g of glycerin diglycidyl ether (Denacol EX313 manufactured by Nagase Chemical Industries, Ltd.), 0.28 g of 10% caustic soda, 0.56 g of a surfactant (Perex OTP manufactured by Kao Soap Co., Ltd.), and 96.9 g of water. After being immersed in the liquid and heat-treated at 240°C for 1 minute, it was treated with the RFL liquid in the same manner as above. Glass fiber (ECG 150 1/3 composition) is γ-
It was immersed in a 5% aqueous dispersion of aminopropyltriethoxysilane, heated at 200°C for 3 minutes, and then subjected to RFL treatment in the same manner as above.
150 3/13 configuration). In addition, below, the testing method for the rubber composition and belt is as follows. A given chloroprene rubber composition was prepared using a 12-inch roll, left for 24 hours, and then subjected to the following tests. (1) Mooney scorch test According to JIS K 6300, a Mooney scorch test was conducted at 120°C using an S-type rotor. (2) Adhesive strength A prescribed rubber composition was molded into a sheet with a thickness of 6.5 mm, and for each of the fiber cords obtained in the reference example, 7 cords were arranged on the sheet in contact with each other and heated at 150℃ for 30 minutes. After vulcanizing under pressure for 24 hours, remove the cords located at both ends, and remove the remaining 5 cords at a peeling speed of 50 mm/min and a peeling angle of 180 mm.
It peeled off at °. With this method, the adhesive strength is 5Kg/5
If the adhesiveness is more than 100%, it is judged that the adhesiveness is good. (3) Heat resistance Using a mold specified in ASTM D 3182-74,
After obtaining a vulcanized sheet by pressure vulcanization at 150°C for 30 minutes, the sheet was aged at 120°C for 168 hours in a gear heat aging tester according to JIS K 6301. Change rate of elongation at break E _B was measured. (4) Compression fatigue resistance and heat generation Rubber pressure-cured at 150°C for 30 minutes was ASTM D
According to 6321, 24 lb load, 4.4 mm stroke, 100°C temperature using Gutudoritsu flexometer.
A compression fatigue test was conducted at , and the permanent set and heat generation after 25 minutes were measured. (5) Blooming property The sample rubber used in the adhesion test was left at 25°C for one month and then visually observed. (6) Belt adhesive strength As an example of a toothed belt is shown in FIG. An outer covering layer 4 is provided on the surface of. Therefore, in measuring the adhesive strength, two cords near the center of the belt were separated from the other cords by 3 pitches, pulled out at a pulling speed of 50 mm/min, and the strength was measured. An example of the V-belt is shown in Figure 2.
It is composed of an adhesive rubber layer 5 and a holding rubber layer 2 from the front surface to the bottom surface, and a cord is embedded in the adhesive rubber layer, and an outer covering 4 is provided on the front surface and the bottom surface. In measuring the adhesive strength of such a V-belt, after removing the layer above the adhesive rubber layer, select three cords near the center of the belt,
Pull out two of them at both ends, peeling speed 50mm/min,
It was peeled off at a peeling angle of 180° and its strength was measured. (7) Belt high temperature durability In the case of a toothed belt, a driving pulley with 16 teeth and a driven pulley with 32 teeth are used, and the driven side load is 3 horsepower, the set weight is 50 kg, and the driving side rotation speed.
The belt was driven at 6000 rpm and an ambient temperature of 120°C, and the time until cracks appeared on the back of the belt was measured. In the case of a V-belt, an idler pulley with a diameter of 70 mm is arranged in addition to a drive pulley with a diameter of 100 mm and a driven pulley. The load on the driven side is 10 horsepower, the set weight is 40 kg, and the rotation speed on the driving side is 4800 rpm. The belt was driven and the time until cracks appeared on the bottom of the belt was measured. Examples of chloroprene rubber compositions and belts that can be used in the present invention are listed below, where parts mean parts by weight. Example 1 Neoprene TRT (non-sulfur modified) 100 parts Stearic acid 0.5 Magnesium oxide 4 Zinc oxide 5 Anti-aging agent 2 FEF carbon 50 Plasticizer 5 Non-sulfur modified chloroprene rubber composition further containing the components shown in Table 1. The test results for the products are shown in Table 1. Experiment numbers 1, 2, and 3, which are non-sulfur-modified chloroprene rubber compositions containing a thiuram compound and nickel salt, were combined with non-sulfur-modified chloroprene rubber compositions of comparative experiment numbers 4, 5, and 7, which do not contain nickel salt. In comparison, the vulcanized product of the rubber composition used in the present invention clearly has excellent adhesion to various fibers and provides a power transmission belt with excellent high-temperature durability. On the other hand, Comparative Example Experiment No. 6 contains sulfur and has good adhesion to fibers, but has poor heat resistance, so it is not suitable for manufacturing power transmission belts used at high temperatures. Example 2 Neoprene W (non-sulfur modified) 100 parts Stearic acid 0.5 Magnesium oxide 4 Zinc oxide 5 Anti-aging agent 2 FEF carbon 50 Plasticizer 5 Non-sulfur modified chloroprene rubber composition further containing the components shown in Table 2. The test results for the products are shown in Table 2. Comparative examples show that when a thiuram compound is not used in combination with nickel carbamate, bloom occurs when 1.5 parts of the thiuram compound is contained per 100 parts of rubber, and becomes noticeable when it is 3 parts or more. However, according to the present invention, it has been shown that by using both in combination, bloom is completely inhibited. Also, when nickel xanthate is used, bloom is suppressed and adhesion is improved. Therefore, the chloroprene rubber composition according to this example also provides a power transmission belt with excellent high-temperature durability. Example 3 Table 3 shows the test results for the chloroprene rubber compositions shown in Table 3. A rubber mixture containing 50% by weight or more of non-sulfur-modified chloroprene rubber can also be produced by using a thiuram compound and a nickel salt in combination, while maintaining the advantages of chloroprene rubber such as heat resistance and compression fatigue resistance. This provides a power transmission belt with significantly improved adhesion and excellent high-temperature durability. Example 4 The non-sulfur modified chloroprene rubber composition of Experiment No. 1 in Table 3 was used for the holding rubber layer, and as a comparative example,
Table 3 Experiment No. 5 and the following composition (A) Neoprene GN (sulfur modified) 100 parts Stearic acid 0.5 Magnesium oxide 4 Zinc oxide 5 Anti-aging agent 2 FEF carbon 50 Plasticizer 5 Sulfur-modified chloroprene rubber compositions, respectively. Using the conventional method, heat and pressurize in a mold,
I made the following toothed belt. Belt shape: AL type Belt circumference: 1056.6mm Belt width: 19mm Cord layer: Glass cord according to the reference example Outer layer: Twill weave with a total denier of 13500 denier/cm ² treated the same as the nylon cord according to the reference example Nylon woven fabric Table 4 shows the adhesive strength and high temperature durability of this belt. It is clear that the belt of the present invention has significantly superior adhesive strength and high temperature durability. Example 5 The rubber composition of Example 1 Experiment No. 1 was used as the adhesive rubber, and the following composition (B) was used as the holding rubber layer: Neoprene TRT (non-sulfur modified) 100 parts Stearic acid 0.5 Magnesium oxide 4 Zinc oxide 5 FEF carbon 35 Nylon A non-sulfur-modified chloroprene rubber composition consisting of short fibers, 5 plasticizers, 5 nickel dibutyl dithiocarbamates, 2 tetramethylthiuram disulfide, 5 ethylene thiourea, 1.2 anti-aging agent, and 2 anti-aging agents was heated and pressurized in a mold in a conventional manner. I made the following V-belt. Belt shape: FM type low edge type Belt circumference: 914.4mm Cord layer: Polyaramid cord according to reference example Outer layer: 0.6mm thick plain woven cotton fabric coated with the same rubber as the adhesive rubber layer As a comparative example, The adhesive rubber layer contains the chloroprene rubber composition shown in the first test number 6, and the holding rubber layer contains the following composition (C): Neoprene GN (sulfur modified) 100 parts Stearic acid 0.5

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[Table] V-belts having the same shape as above were manufactured using non-sulfur-modified chloroprene rubber compositions consisting of 4 magnesium oxide, 5 zinc oxide, 35 FEF carbon, 20 short nylon fibers, 5 plasticizers, and 2 anti-aging agents. Table 4 shows the adhesive strength and high temperature durability of the cords for these belts. It is clear that the belt of the present invention has significantly excellent adhesive strength and high-temperature durability, whereas the belt of the comparative example has poor high-temperature durability.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view showing an example of a toothed belt, and FIG. 2 is a cross-sectional view showing an example of a V-belt. DESCRIPTION OF SYMBOLS 1... Teeth, 2... Holding rubber layer, 3... Cord, 4... Outer covering layer, 5... Adhesive rubber layer.

Claims (1)

[Scope of Claims] 1. A power transmission belt consisting of a fiber layer and an elastic layer, wherein the elastic layer comprises (a) 100 parts by weight of rubber containing 50% by weight or more of non-sulfur-modified chloroprene rubber; (b) general rubber; formula (However, R ¹ is each independently an alkyl group,
It represents a nitrogen-containing carbon ring formed by an aryl group or two R ¹ together with nitrogen, and x represents an integer of 1 to 6. ) 2 to 15 parts by weight of a thiuram compound represented by (c) general formula (However, R ² is each independently an alkyl group,
Aryl group, cycloalkyl group or two ^R2
indicates a nitrogen-containing carbon ring formed with nitrogen. ) and the general formula (However, R ³ represents an alkyl group.) It is characterized by being made of a vulcanized rubber of a rubber composition containing 0.3 to 5 parts by weight of at least one nickel salt selected from nickel xanthate represented by transmission belt.