Transmission belt

Abstract

To provide a transmission belt that is high in water resistance and crack growth resistance while maintaining handleability, and is excellent even in slip prevention performance.SOLUTION: A power transmission belt according to one embodiment of the present invention is a power transmission belt comprising a belt body made of an elastomer, where a main component of the elastomer is thermoplastic polyurethane, and has a 6% modulus of 2.5 MPa or more and less than 3 MPa.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a power transmission belt. [Background technology]

[0002] Various types of power transmission belts, such as round belts and V-belts, are widely used for power transmission purposes. These power transmission belts are endless and are used by being stretched between a pair of pulleys.

[0003] A power transmission belt is required to have high strength because accurate power transmission becomes difficult if a crack occurs in the belt, and high-strength transmission belts have been proposed (see, for example, Japanese Patent Application Laid-Open No. 7-77628). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 7-77628 Summary of the Invention [Problem to be solved by the invention]

[0005] The power transmission belt described in the above publication has fibrous reinforcing materials dispersed in a belt body made of an elastomer, thereby realizing high strength and high elasticity.

[0006] However, it is known that in conventional power transmission belts, once a crack occurs in the belt body, the crack tends to grow and eventually break in a relatively short period of time.

[0007] Furthermore, power transmission belts used in fields such as home appliances, logistics, semiconductor manufacturing, and printing equipment may be immersed in water, for example. In such an environment, cracks tend to grow particularly quickly, and power transmission belts with high water resistance and crack growth resistance are therefore required.

[0008] In response to this, for example, increasing the hardness of the power transmission belt can prevent the progression of this crack; however, a belt with high hardness has little elongation even when tension is applied, making it difficult to stretch the belt between a pair of pulleys and making it difficult to handle.

[0009] Furthermore, when used immersed in water, the transmission belt may be prone to slippage. Here, "slip" refers to the phenomenon in which the rotation speed of the driven pulley is insufficient relative to the rotation speed of the driving pulley. When slippage occurs, the transmission capacity of the equipment becomes insufficient, and the equipment will no longer be able to fulfill its original required functions.

[0010] The present invention has been made in view of the above-mentioned inconveniences, and has an object to provide a power transmission belt which has high water resistance and crack propagation resistance, and also has excellent anti-slip performance, while maintaining ease of handling. [Means for solving the problem]

[0011] A power transmission belt according to one embodiment of the present invention is a power transmission belt including a belt body made of an elastomer, the main component of the elastomer being thermoplastic polyurethane, and having a 6% modulus of 2.5 MPa or more and less than 3 MPa. Effect of the Invention

[0012] The power transmission belt of the present invention has high water resistance and crack growth resistance while maintaining ease of handling, and also has excellent anti-slip performance. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram showing a state in which a transmission belt according to one embodiment of the present invention is used. [Diagram 2] FIG. 2 is a graph for explaining the melt viscosity of an elastomer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] [Description of the embodiment of the present invention] First, the embodiments of the present invention will be listed and described.

[0015] (1) A power transmission belt according to one embodiment of the present invention is a power transmission belt including a belt body made of an elastomer, the main component of the elastomer being thermoplastic polyurethane and having a 6% modulus of 2.5 MPa or more and less than 3 MPa.

[0016] The main component of the elastomer constituting the belt body of the power transmission belt is thermoplastic polyurethane, which enhances water resistance and crack growth resistance. In addition, by using thermoplastic polyurethane as the main component, the hardness of the belt body is unlikely to increase, and the power transmission belt is easy to handle. On the other hand, when the main component of the elastomer of the belt body is thermoplastic polyurethane, the slip prevention performance is likely to decrease. However, the present inventors have found that by setting the 6% modulus within the above range, water resistance, crack growth resistance, and slip prevention performance can be achieved at the same time. In other words, the belt is also excellent in slip prevention performance.

[0017] (2) In the power transmission belt of (1) above, the JIS-A hardness of the belt body is preferably equal to or greater than 80 and equal to or less than 99. By setting the JIS-A hardness of the belt body within the above range, it is possible to prevent deterioration in handling ease while maintaining the transmission force.

[0018] (3) In the power transmission belt of (1) or (2) above, the cross-sectional area of ​​the belt body is 3 mm 2 More than 140mm 2 The following is preferable. By setting the cross-sectional area of ​​the belt body within the above range, water resistance and crack propagation resistance can be improved.

[0019] (4) In the power transmission belt according to any one of (1) to (3), the thermoplastic polyurethane may be a caprolactone-based polyurethane, which can further improve water resistance and crack propagation resistance without increasing the hardness of the belt body.

[0020] (5) In the power transmission belt according to any one of (1) to (3), the elastomer contains two or more types of thermoplastic polyurethanes, and at least one of the two or more types of thermoplastic polyurethanes is a caprolactone-based one. By using two or more types of thermoplastic polyurethanes as the elastomer and at least one of the two or more types of thermoplastic polyurethanes is a caprolactone-based one, the 6% modulus value can be easily controlled to a desired range.

[0021] Here, the term "main component" refers to the component that is contained in the largest amount, preferably a component that is contained in an amount of 50% by mass or more, and more preferably a component that is contained in an amount of 90% by mass or more.

[0022] The "6% modulus" of a power transmission belt is measured by the following procedure. First, the power transmission belt is melt-joined to form an endless (annular) shape. Next, this power transmission belt is stretched between a pair of pulleys and then stretched using a tensile tester. The axial load [N] when the power transmission belt is stretched by 6% is measured, and the axial load is divided by 2 and then multiplied by the cross-sectional area [mm 2 ] to obtain the 6% modulus [MPa].

[0023] "JIS-A hardness" refers to the hardness measured by applying the indenter of an A-type hardness tester to the surface of a fixed belt in accordance with JIS-K-7312:1996 (Method A).

[0024] [Details of the embodiment of the present invention] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A power transmission belt according to an embodiment of the present invention will be described with reference to the drawings.

[0025] The power transmission belt 1 shown in FIG. 1 is configured to be endless, and is used by being stretched between a driving pulley X1 and a driven pulley X2. When the driving pulley X1 is driven to rotate by a driving device (not shown), the rotation sends the power transmission belt 1, causing the driven pulley X2 to rotate. This allows the rotation of the driving pulley X1 to be transmitted as the rotation of the driven pulley X2. Note that, although the driving pulley X1 and the driven pulley X2 have approximately the same diameter in FIG. 1, they can also be made to have different diameters to change the number of rotations.

[0026] The power transmission belt 1 includes a belt body 10 made of an elastomer. The power transmission belt 1 is configured of a single layer of the belt body 10. The total length (circumferential length) of the power transmission belt 1 is appropriately set according to the application, and can be, for example, 300 mm or more and 1000 mm or less.

[0027] <Belt body> The cross section of the belt body 10 can be circular (round belt), trapezoidal (V belt), rectangular (flat belt), or the like, but it is preferable that the cross section of the belt body 10 is circular. In the power transmission belt 1, the water resistance and crack propagation resistance can be particularly improved in the belt body 10 having the circular cross section.

[0028] The lower limit of the cross-sectional area of ​​the belt body 10 is 3 mm 2 is preferred, 7mm 2 On the other hand, the upper limit of the cross-sectional area of ​​the belt body 10 is 140 mm 2 is preferred, 130 mm 2 is more preferable, and 100 mm 2 In the power transmission belt 1, the water resistance and crack propagation resistance can be particularly improved in the belt body 10 having the cross-sectional area within the above range.

[0029] A tension is applied to the belt body 10. The tension can be set to, for example, a value that results in an elongation rate of 3% to 10% of the natural length of the belt body 10. In particular, the elongation rate is often in the range of 3% to 7%. If the tension is below the lower limit, the power transmission belt 1 may not be able to sufficiently transmit the power of the driving pulley X1 to the driven pulley X2. Conversely, if the tension exceeds the upper limit, it may become difficult to stretch the power transmission belt 1 between the driving pulley X1 and the driven pulley X2, which may reduce the ease of handling.

[0030] (Elastomer) Thermoplastic polyurethane is the main component of the elastomer constituting the belt body 10. As the thermoplastic polyurethane, for example, caprolactone-based polyurethane, polycarbonate-based polyurethane, ether-based polyurethane, etc. can be used.

[0031] The thermoplastic polyurethane is preferably a caprolactone-based one. By using a caprolactone-based thermoplastic polyurethane in this way, the water resistance and crack growth resistance can be further improved without increasing the hardness of the belt body 10. As the thermoplastic caprolactone-based polyurethane, for example, one using caprolactone ester as a polyol type, diphenylmethane diisocyanate (MDI) as an isocyanate type, and 1,4-butanediol (1,4BD) as a crosslinking agent type can be used.

[0032] The elastomer may contain two or more types of thermoplastic polyurethane. At least one of the two or more types of thermoplastic polyurethane is preferably caprolactone-based, and more preferably all of them are caprolactone-based. By using two or more types of thermoplastic polyurethane as the elastomer and at least one of the two or more types of thermoplastic polyurethane is caprolactone-based, the value of 6% modulus described later can be easily controlled to a desired range.

[0033] Although the elastomer may contain other types of elastomers as sub-components, it is preferred that the elastomer is composed solely of thermoplastic polyurethane.

[0034] When the melt viscosity of the above elastomer is measured by the temperature rise method, a temperature-melt viscosity curve such as that shown in Figure 2 can be obtained. Figure 2 shows examples of temperature-melt viscosity curves for three types of elastomers. The melt viscosity of an elastomer is measured by the temperature rise method using a commercially available high-low flow tester (for example, Shimadzu's CFT-500D), preheating to a specified temperature (for example, 120°C) for 180 seconds, and then extruding the elastomer from a die (diameter 1 mm, depth 1 mm) with a load of 10 kg while increasing the temperature at a rate of 5°C / min. The viscosity at that temperature is calculated from the amount extruded per unit time. The viscosity η [Pa·s] is calculated by the shear stress τ [Pa] and shear rate γ (s -1 ) can be converted into η=τ / γ.

[0035] As shown in FIG. 2, the viscosity decreases with increasing temperature. The lower limit of the first melting temperature at which the elastomer has a viscosity of 100,000 Pa·S in the melt viscosity measurement by the temperature rise method is preferably 150°C, more preferably 170°C, even more preferably 180°C, and particularly preferably 190°C. The upper limit of the second melting temperature at which the elastomer has a viscosity of 1,000 Pa·S in the melt viscosity measurement by the temperature rise method is preferably 240°C, more preferably 230°C, and even more preferably 220°C. If the first melting temperature is below the lower limit, the heat resistance of the belt body 10 may decrease. Conversely, if the second melting temperature exceeds the upper limit, it becomes necessary to join the belt body 10 to make it endless at a high temperature, which may decrease workability.

[0036] The upper limit of the temperature difference between the first melting temperature and the second melting temperature is preferably 30° C., more preferably 25° C., and even more preferably 20° C. By setting the temperature difference between the first melting temperature and the second melting temperature to the upper limit or less in this manner, the variation in the molecular weight distribution of the polyurethane is suppressed, and the water resistance and crack propagation resistance are further improved. On the other hand, the lower limit of the temperature difference is not particularly limited, but the temperature difference is usually 10° C. or more.

[0037] The lower limit of the number average molecular weight of the main component of the elastomer is preferably 30,000, more preferably 50,000, further preferably 60,000, and particularly preferably 65,000. On the other hand, the upper limit of the number average molecular weight is preferably 80,000, more preferably 75,000, and further preferably 70,000. If the number average molecular weight is less than the lower limit, the first melting temperature is likely to decrease. In this case, the strength of the belt body 10 is likely to decrease, and there is a risk of early breakage. Conversely, if the number average molecular weight exceeds the upper limit, the second melting temperature is likely to increase. In this case, it becomes difficult to stretch the transmission belt 1 between the driving pulley X1 and the driven pulley X2, and there is a risk of deterioration in handleability.

[0038] The lower limit of the weight average molecular weight of the main component of the elastomer is preferably 70,000, more preferably 160,000, and even more preferably 170,000. On the other hand, the upper limit of the weight average molecular weight is preferably 240,000, more preferably 200,000, and even more preferably 190,000. If the weight average molecular weight is less than the lower limit, the temperature difference between the first melting temperature and the second melting temperature is likely to be large, and the strength of the belt body 10 is likely to be reduced, which may lead to early breakage. Conversely, if the weight average molecular weight exceeds the upper limit, the hardness of the transmission belt 1 may be too high, which may lead to reduced handleability.

[0039] By setting the number average molecular weight and weight average molecular weight of the main component of the elastomer within the above ranges, it is easy to set the temperature difference between the first melting temperature and the second melting temperature to less than 30°C within a range in which the first melting temperature is 150°C or higher and the second melting temperature is 240°C or lower.

[0040] The lower limit of the JIS-A hardness of the belt body 10 is preferably 80, and more preferably 85. On the other hand, the upper limit of the JIS-A hardness is preferably 99, and more preferably 96. If the JIS-A hardness is less than the lower limit, it becomes difficult to apply sufficient tension to the belt body 10, and the transmission power of the power transmission belt 1 may decrease. On the other hand, if the JIS-A hardness exceeds the upper limit, elongation is small even when tension is applied, and therefore it becomes difficult to wrap the power transmission belt 1 between the driving pulley X1 and the driven pulley X2, and handleability may decrease.

[0041] The JIS-A hardness of the belt body 10 can be controlled, for example, by selecting the main component of the elastomer. When two or more types of elastomers are used, the JIS-A hardness may be controlled by using elastomers each having a desired range of JIS-A hardness.

[0042] The belt body 10 may contain a lubricant or the like that is usually added to a transmission belt whose main component is urethane, within a range that does not impair the effect of the transmission belt 1. An example of the lubricant is fatty acid amide. By adding the lubricant, when a sudden load is applied to the transmission belt 1, the transmission belt 1 slips, and the transmission belt 1 can be prevented from being cut.

[0043] The 6% modulus of the power transmission belt 1 is 2.5 MPa or more, and more preferably 2.6 MPa or more. On the other hand, the 6% modulus of the power transmission belt 1 is less than 3 MPa, and more preferably less than 2.9 MPa. If the 6% modulus is less than the lower limit, it may be difficult to ensure water resistance and crack growth resistance. Conversely, if the 6% modulus exceeds the upper limit, slip prevention performance may be insufficient. Note that the modulus can be measured and determined at, for example, 10%, but as described above, since power transmission belts are often used in an elongation range of 3% to 7%, 6%, which is near the upper limit of this range, is used. By using the 6% modulus as an index in this way, it is easy to precisely control slip prevention performance.

[0044] The upper limit of the slip ratio of the power transmission belt 1 at a load torque of 0.6 N m is preferably 7%, and more preferably 6.5%. If the slip ratio exceeds the upper limit, excessive slip occurs during the running of the power transmission belt 1, which may result in insufficient rotation speed and other problems that may not fully satisfy the functionality of the equipment. On the other hand, the lower limit of the slip ratio is not particularly limited, and the lower the better.

[0045] The upper limit of the slip ratio of the power transmission belt 1 at a load torque of 1.0 N m is preferably 12.5%, and more preferably 11%. If the slip ratio exceeds the upper limit, excessive slip occurs during the running of the power transmission belt 1, which may result in insufficient rotation speed and other problems that may not fully satisfy the functionality of the equipment. On the other hand, the lower limit of the slip ratio is not particularly limited, and the lower the better.

[0046] The above-mentioned "slip ratio" is measured using the following procedure. First, both ends of the belt are fused together to create an endless power transmission belt. Next, this power transmission belt is stretched so that its elongation ratio is 6%, and then stretched between a pair of pulleys. The rotation speed of the driving pulley is fixed at 1600 rpm, and the load torque of the driven pulley is set to 0.6 N·m or 1.0 N·m, and the rotation speed [rpm] of the driven pulley is measured. The slip ratio at each load torque is calculated using the following formula 1, where the rotation speed of the driven pulley is a [rpm]. Slip ratio = (1600-a) / 1600×100[%] 1

[0047] <Manufacturing method> The belt body 10 of the power transmission belt 1 can be produced, for example, by feeding urethane pellets, which are the raw material, into an extruder and extruding the pellets using a screw.

[0048] Specifically, first, urethane pellets are prepared as raw materials. When the elastomer contains two or more types of thermoplastic polyurethane, the pellets of the two or more types of urethane are weighed out in predetermined amounts using a weighing machine, mixed, and stirred using a stirrer to obtain raw materials. The raw materials are fed into an extruder set at a predetermined temperature, melted and kneaded using a screw, extruded from a die (die) according to the desired cross-sectional shape, and then cooled and solidified to obtain a molded belt body 10.

[0049] <Advantages> In the power transmission belt 1, the main component of the elastomer constituting the belt body 10 is thermoplastic polyurethane, which enhances water resistance and crack growth resistance. In addition, by using thermoplastic polyurethane as the main component, the hardness of the belt body 10 is unlikely to increase, and the power transmission belt 1 is therefore easy to handle. On the other hand, if the main component of the elastomer of the belt body 10 is thermoplastic polyurethane, the slip prevention performance is likely to decrease, but by setting the 6% modulus within the above range, water resistance, crack growth resistance, and slip prevention performance can be achieved at the same time. In other words, the belt 1 is also excellent in slip prevention performance.

[0050] [Other embodiments] The present invention is not limited to the above-described embodiment, and can be embodied in various other forms in addition to the above-described forms with various modifications and improvements.

[0051] In the above embodiment, the power transmission belt is configured as a single belt body layer, but the belt body may have a multi-layer structure. In this case, at least the belt body layer constituting the main layer is made of the elastomer described in the above embodiment. Here, the "main layer" means the layer having the largest cross-sectional area, preferably the layer occupying 50% or more of the cross-sectional area, and in the case of a round belt having a circular cross section, it is usually the inner layer.

[0052] The belt body may have a cavity inside. By providing a cavity inside the belt body, it is possible to reduce the weight while maintaining the strength.

[0053] The power transmission belt of the present invention may have a configuration other than the belt body. For example, the power transmission belt may have one or more core bodies inside the belt body. Examples of the core body include a steel cord, a glass fiber cord, a polyester fiber cord, and an aromatic polyamide fiber cord.

[0054] Alternatively, the power transmission belt may include a cover layer that covers the outer surface of the belt body. As the cover layer, for example, a polyester resin layer can be mentioned. EXAMPLES

[0055] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0056] [No.1] Pellets of two types of thermoplastic caprolactone-based polyurethane resins shown in Table 1 were weighed out using a weighing machine to have a mass ratio of 10:3, and stirred using a stirrer to prepare raw materials. These raw materials were fed into an extrusion molding machine equipped with a screw, melted and kneaded, and extruded to prepare an elastomer belt body (circular cross section: diameter 5 mm) mainly composed of thermoplastic polyurethane. The inlet temperature of the extrusion molding machine was set to 180°C, and the outlet temperature was set to 220°C. The number average molecular weight and weight average molecular weight of the prepared belt body are as shown in Table 1. In addition, this belt body was cut to a predetermined length, and both ends were melt-joined in a conventional manner to form an endless shape, and a transmission belt (round belt) No. 1 consisting of only the belt body was prepared.

[0057] The JIS-A hardness of each of the two types of polyurethane used in manufacturing the No. 1 belt body and the JIS-A hardness of the No. 1 power transmission belt were measured by applying the indenter of an A-type hardness tester to the belt surface in accordance with JIS-K-7312:1996 (Method A). The results are shown in Table 1. The JIS-A hardness of the polyurethanes was measured on belt bodies molded in the same manner as the No. 1 power transmission belt body, except that each polyurethane was used alone as a raw material.

[0058] The 6% modulus of the polyurethane and the No. 1 power transmission belt was measured by the following procedure. The power transmission belt, which had been prepared so as to have an endless circumference of approximately 880 mm, was stretched using a tensile tester ("Autograph (product name)" manufactured by Shimadzu Corporation). Specifically, a pair of pulleys was fixed to the crosshead of the tensile tester via a jig, and the power transmission belt was stretched between the pair of pulleys. One of the pulley shafts was then moved to stretch the power transmission belt, thereby measuring the elongation rate and axial load. The axial load [N] when the power transmission belt was stretched by 6% was divided by 2, and the value was then multiplied by the cross-sectional area [mm 2 The results are shown in Table 1.

[0059] The above-mentioned "elongation rate" refers to a value calculated from the natural length L0 (length when no tension is applied) of the transmission belt and the length Lt when it is stretched, using the following formula 2. Here, the natural length L0 can be calculated from the distance between the driving pulley X1 and the driven pulley X2 and the diameters of the driving pulley X1 and the driven pulley X2 at the moment (just before) when the axial load is applied from a state in which the axial load is substantially zero, in the measurement using the above-mentioned tensile tester. For example, the natural length L0 of the belt body 10 shown in FIG. 1 is twice the center distance between the driving pulley X1 and the driven pulley X2 at the above-mentioned moment, plus half the circumference of the driving pulley X1 and half the circumference of the driven pulley X2. The length Lt when it is stretched can also be calculated in the same manner according to the center distance of the pulleys at that time. Elongation rate=(Lt-L0) / L0×100[%]...2

[0060] The elastomer (pellets of polyurethane resin) used in the manufacture of the belt body was subjected to melt viscosity measurement by the temperature rise method. The melt viscosity measurement of the elastomer by the temperature rise method was performed using a commercially available high-low flow tester (Shimadzu Corporation's "CFT-500D"), preheated at 120°C for 180 seconds, and then extruded from a die (diameter 1 mm, depth 1 mm) with a load of 10 kg while increasing the temperature at a rate of 5°C / min. The viscosity calculated from the amount extruded per unit time at this time was taken as the viscosity at that temperature. The results are shown in Table 1.

[0061] [No.2] A belt body was manufactured in the same manner as in No. 1, except that only one type of thermoplastic adipate-based polyurethane was used as the raw material polyurethane resin used in manufacturing the belt body, and a power transmission belt No. 2 was prepared.

[0062] The JIS-A hardness, 6% modulus, and melt viscosity by the temperature rise method were measured for the No. 2 power transmission belt in the same manner as for the No. 1. The results are shown in Table 1.

[0063] [No.3] A belt body was manufactured in the same manner as in No. 1, except that only one of the two types of thermoplastic caprolactone-based polyurethane used in No. 1 was used as the raw material polyurethane resin used to manufacture the belt body, and thus a power transmission belt No. 3 was prepared.

[0064] The JIS-A hardness, 6% modulus, and melt viscosity by the temperature rise method were measured for the No. 3 power transmission belt in the same manner as for the No. 1. The results are shown in Table 1.

[0065] [No.4] A belt body was manufactured in the same manner as in No. 1, except that the other type of the two types of thermoplastic caprolactone-based polyurethane used in No. 1 was used as the raw material polyurethane resin used to manufacture the belt body, and a power transmission belt No. 4 was prepared.

[0066] The JIS-A hardness, 6% modulus, and melt viscosity by the temperature rise method were measured for the No. 4 power transmission belt in the same manner as for the No. 1. The results are shown in Table 1.

[0067] [Table 1]

[0068] [evaluation] (Anti-slip performance) Transmission belts No.1 to No.4, which were prepared so that they had an endless circumference of approximately 580 mm, were stretched between the driving pulley X1 and the driven pulley X2 shown in Figure 1. The diameters of the driving pulley X1 and the driven pulley X2 were each 44 mm, the rotation speed of the driving pulley X1 was 1600 rpm, and the elongation rate of the transmission belt was 6%. The load torque of the driven pulley X2 was set to 0.6 N m or 1.0 N m, and the rotation speed [rpm] of the driven pulley X2 was measured.

[0069] The slip ratio was calculated using the following formula 3, with the rotation speed of the driven pulley X2 being a [rpm]. The results are shown in Table 1. Slip ratio = (1600-a) / 1600×100[%] 3

[0070] The slip ratio was judged according to the following criteria. A: The slip ratio is less than 6.5% when the load torque is 0.6 N m, and less than 11% when the load torque is 1.0 N m. B: The slip ratio is 6.5% or more and less than 7% when the load torque is 0.6 N m, and 11% or more and less than 12.5% ​​when the load torque is 1.0 N m. C: Other than A and B above (slip rate is higher than A and B).

[0071] (Water resistance and crack growth resistance) Transmission belts No. 1 to No. 4, which were prepared so as to have an endless shape with a circumferential length of approximately 880 mm, were uniformly cut with a depth of 1.5 mm in four places, immersed in hot water at 98°C for 6.5 days, and then stretched between a driving pulley X1 and a driven pulley X2 shown in Fig. 1. The diameter of the driving pulley X1 was 24 mm, the diameter of the driven pulley X2 was 37 mm, the distance (axis distance) between the driving pulley X1 and the driven pulley X2 was 410 mm, the rotation speed of the driving pulley X1 was 2750 rpm, and the elongation rate of the transmission belt was 15%.

[0072] The power transmission belts were run with the above-mentioned configuration. For No.1 and No.3, the power transmission belts did not break even after 500 hours of running, but for No.2 and No.4, the power transmission belts broke after less than 24 hours of running. From this result, No.1 and No.3 were judged to have high water resistance and crack growth resistance (evaluation A), while No.2 and No.4 were judged to have low water resistance and crack growth resistance (evaluation C) (see Table 1).

[0073] The results in Table 1 show that the No. 1 power transmission belt, whose main component of the elastomer is thermoplastic polyurethane and whose 6% modulus is 2.5 MPa or more and less than 3 MPa, has high water resistance and crack propagation resistance, as well as excellent slip prevention performance. [Industrial Applicability]

[0074] The power transmission belt of the present invention has high water resistance and crack growth resistance while maintaining ease of handling, and also has excellent anti-slip performance. [Explanation of symbols]

[0075] 1 Transmission belt 10 Belt body X1 Drive pulley X2 driven pulley

Claims

1. A power transmission belt having an elastomer belt body, The main component of the elastomer is a thermoplastic polyurethane, A power transmission belt having a 6% modulus of 2.5 MPa or more and less than 3 MPa.

2. 2. The power transmission belt according to claim 1, wherein the belt body has a JIS-A hardness of 80 or more and 99 or less.

3. The cross-sectional area of ​​the belt body is 3 mm ２ More than 140mm ２ 3. The power transmission belt according to claim 1 or 2, wherein:

4. 3. The power transmission belt according to claim 1, wherein the thermoplastic polyurethane is a caprolactone-based thermoplastic polyurethane.

5. the elastomer comprises two or more thermoplastic polyurethanes, 3. The power transmission belt according to claim 1, wherein at least one of the two or more thermoplastic polyurethanes is a caprolactone-based thermoplastic polyurethane.

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