Toothed belt and method for manufacturing the same

Abstract

To provide a toothed belt that can maintain conductivity (antistatic properties) during operation over a long period without reducing the belt's lifespan or cost-effectiveness. [Solution] A toothed belt 1 comprises a back portion 1c in which a core wire 5 extending in the circumferential direction of the belt is embedded, and a plurality of teeth 1a formed on the inner circumferential surface of the back portion 1c at intervals in the circumferential direction of the belt, a back rubber layer 6 formed on the outer circumferential side of the belt relative to the core wire 5, and a first rubber layer and a second rubber layer formed on the inner circumferential side of the belt relative to the core wire 5, wherein the back portion 1c includes the back rubber layer 6, the teeth 1a are formed of the first rubber layer and the second rubber layer interposed between the first rubber layer and the core wire 5, the first rubber layer is formed of a first crosslinked rubber composition containing a first rubber component and a first carbon black, and the DBP absorption amount of the first carbon black and the mass ratio of the first carbon black are adjusted to satisfy predetermined requirements.

Description

[Technical Field]

[0001] The present invention relates to a toothed belt with conductivity and a method for manufacturing the same. [Background technology]

[0002] Power transmission belts are broadly classified into friction belts and meshing belts. Examples of friction belts include flat belts, V-belts, and V-ribbed belts, while examples of meshing belts include toothed belts. A toothed belt has a back portion with a core wire embedded approximately parallel to the belt's circumference, teeth arranged at predetermined intervals in the belt's circumference, and a toothed fabric that forms the surface of the teeth. The teeth of a toothed belt transmit power by fitting into a pulley that has grooves opposite to the teeth. Toothed belts are increasingly being used in industrial machinery, internal combustion engines of automobiles, and rear-wheel drive systems of motorcycles, taking advantage of their characteristics of not causing slippage between the pulley and the belt and being able to reliably transmit power even under high loads.

[0003] In particular, as a toothed belt that can achieve both the rigidity (deformability) of the teeth and the flexibility (suppleness) of the belt, which are in a contradictory relationship, Japanese Patent Publication No. 7235919 (Patent Document 1) discloses a toothed belt in which the teeth of the toothed belt are formed of a toothed fabric, a first rubber layer formed along the toothed fabric, and a second rubber layer formed between the first rubber layer and the core wire, and the elastic modulus of the first rubber layer is adjusted to be greater than that of the second rubber layer.

[0004] However, conventional toothed belts are not conductive, and static electricity can accumulate during use due to repeated contact and separation between the toothed belt and the pulley. This accumulated static electricity can cause sparks (electrical discharges), potentially damaging electronic equipment or leading to ignition or explosion. Therefore, conductivity is required for toothed belts depending on the application. If the toothed belt is conductive, static electricity is slowly discharged to the outside through the pulley, thus preventing the generation of sparks.

[0005] A common method for imparting conductivity to toothed belts has been to impart conductivity (antistatic properties) to the tooth fabric, which is the outer surface in contact with the pulley, in order to slowly discharge static electricity to the outside through the pulley and prevent the generation of sparks. For example, methods such as using conductive threads in the threads that make up the tooth fabric, or adding a conductive substance to the adhesive treatment liquid (RFL treatment liquid) for the tooth fabric to adhere the conductive substance to the tooth fabric are known. For example, Japanese Patent Publication No. 2017-512957 (Patent Document 2) discloses a conductive belt that maintains conductivity for a long service life in a harsh load environment, comprising an elastomer belt body, conductive tensile cords in a cord layer that reinforces the belt body, an outer layer of a conductive thermoplastic material, and a conductive canvas layer located between the tensile cord layer and the outer layer, providing electrical continuity between the outer layer and the tensile cords. This document also states that, as an alternative to conductive canvas, conductivity may be imparted to non-conductive canvas by immersion treatment with conductive RFL. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 7235919 [Patent Document 2] Special Publication No. 2017-512957 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, in methods using conductive threads, such as the conductive canvas layer in Patent Document 2, the antistatic properties cannot be maintained if the conductive threads are cut along with the wear of the tooth fabric due to belt operation. Also, in methods where a conductive substance is added to the adhesive treatment liquid (RFL treatment liquid) to adhere the conductive substance to the tooth fabric (non-conductive canvas), the adhesion decreases and the belt's running life decreases as the concentration of the conductive substance increases and the RFL solid content concentration decreases relatively. Furthermore, both methods are expensive in terms of manufacturing costs (material costs). Moreover, in Patent Document 2, a conductive path is secured by constructing the entire transmission belt with conductive materials, so compared to a transmission belt made of non-conductive materials, it is not only less economical but also less strong (strength related to the belt's running life). In particular, when a woven fabric containing conductive fibers is used as the conductive canvas, there was a drawback that the conductivity was lost relatively quickly, possibly because the contact area between the conductive fibers and the pulley was small.

[0008] Therefore, the object of the present invention is to provide a toothed belt and a method for manufacturing the same that can maintain conductivity (antistatic properties) during operation over a long period of time without reducing the belt's running life and economic efficiency.

[0009] Another object of the present invention is to provide a toothed belt that has excellent processability and deformation resistance and can suppress tooth skipping, and a method for manufacturing the same. [Means for solving the problem]

[0010] To achieve the above objectives, the present inventors have found that by forming the teeth of a toothed belt with a toothed fabric, a first rubber layer formed along the toothed fabric, and a second rubber layer formed between the first rubber layer and the core wire, and by forming the first rubber layer with a rubber composition containing carbon black, and by adjusting the DBP absorption amount (DBP oil absorption amount) and ratio of the carbon black, it is possible to provide a toothed belt that can maintain conductivity (antistatic properties) during operation for a long period of time without reducing the belt's running life and economic efficiency, and have completed the present invention.

[0011] In other words, the present invention includes the following embodiments.

[0012] Embodiment [1]: A back portion in which a core wire extending along the circumferential direction of the belt is embedded, The inner circumferential surface of the back portion is provided with a plurality of teeth formed at intervals in the circumferential direction of the belt, A toothed belt comprising a back rubber layer formed on the outer circumference side of the belt relative to the core wire, and a first rubber layer and a second rubber layer formed on the inner circumference side of the belt relative to the core wire, The back portion includes the back rubber layer, The tooth portion includes the first rubber layer and the second rubber layer interposed between the first rubber layer and the core wire. The first rubber layer is formed of a first crosslinked rubber composition comprising a first rubber component and a first carbon black, and A toothed belt that satisfies all of the following requirements 1 to 3, where X1 (mL / 100g) is the DBP absorption amount of the first carbon black and Y1 is the mass ratio of the first carbon black to 100 parts by mass of the first rubber component.

[0013] Requirement 1: X1 ≥ 110 Requirement 2: 22 ≤ Y1 ≤ 88 Requirement 3: X1 × Y1 ≥ 9000

[0014] Embodiment [2]: The toothed belt according to Embodiment [1], wherein the second rubber layer is formed of a second crosslinked rubber composition containing a second rubber component, and the proportion of second carbon black in the second crosslinked rubber composition is less than 22 parts by mass per 100 parts by mass of the second rubber component.

[0015] Embodiment [3]: The toothed belt according to Embodiment [2], wherein the second crosslinked rubber composition further comprises a second carbon black, and when the mass ratio of the second carbon black to 100 parts by mass of the second rubber component is Y2, the product of the DBP absorption amount X2 of the second carbon black and the mass ratio Y2 (X2 × Y2) is less than 9000.

[0016] Aspect [4]: The toothed belt according to any one of the aspects [1] to [3], wherein the first rubber component includes a first composite polymer containing a hydrogenated nitrile rubber and a metal salt of an unsaturated carboxylic acid, and the second rubber component includes a second composite polymer containing a hydrogenated nitrile rubber and a metal salt of an unsaturated carboxylic acid.

[0017] Aspect [5]: The toothed belt according to any one of the aspects [1] to [4], wherein the first crosslinked rubber composition further includes first short fibers.

[0018] Aspect [6]: The toothed belt according to any one of the aspects [1] to [5], wherein the elastic modulus of the first rubber layer is greater than that of the second rubber layer.

[0019] Aspect [7]: The toothed belt according to any one of the aspects [1] to [6], wherein the inner peripheral surface of the belt of the first rubber layer is composed of a toothed cloth.

[0020] Aspect [8]: The toothed belt according to any one of the aspects [1] to [7], wherein the electrical resistance value R of the toothed surface of the belt measured by a method conforming to ISO9563 (2015) is 6×10 5 ×L / W (Ω) [L means the electrode distance (mm), and W means the electrode width (mm) (however, when the belt width is smaller than the electrode width, the belt width)], and is as follows.

[0021] Aspect [9]: The toothed belt according to aspect [8], wherein after running for 200 hours under the condition of a load torque of 200 to 250 N·m, the electrical resistance value R of the toothed surface of the belt measured by a method conforming to ISO9563 (2015) is 6×10 5 ×L / W (Ω) [L means the electrode distance (mm), and W means the electrode width (mm) (however, when the belt width is smaller than the electrode width, the belt width)], and is as follows.

[0022] Aspect

[10] : A method for manufacturing a toothed belt according to any one of the aspects [1] to [9], including a preforming step of manufacturing a preform in which an uncrosslinked rubber sheet for forming the first rubber layer and an uncrosslinked rubber sheet for forming the second rubber layer are laminated.

[0023] In this application, the numerical range represented by "A~B" means "A or greater and B or less," and is used to include the values ​​A and B at both ends of that range. [Effects of the Invention]

[0024] In this invention, the teeth of a toothed belt are formed from a toothed fabric, a first rubber layer formed along the toothed fabric, and a second rubber layer formed between the first rubber layer and the core wire. The first rubber layer is formed from a rubber composition containing carbon black, and the amount and ratio of DBP absorption of the carbon black are adjusted. As a result, a toothed belt is provided that can maintain conductivity (antistatic properties) during operation for a long period of time without reducing the belt's running life and economic efficiency. Furthermore, the toothed belt of this invention has excellent processability and deformation resistance, which can suppress tooth skipping. [Brief explanation of the drawing]

[0025] [Figure 1] Figure 1 is a schematic partial cross-sectional perspective view showing an example of a toothed belt according to the present invention. [Figure 2] Figure 2 is a schematic cross-sectional view of the toothed belt shown in Figure 1. [Figure 3] Figure 3 shows the layout for the endurance running test and jumping test of the toothed belt obtained in the embodiment. [Figure 4] Figure 4 is a schematic diagram illustrating the method for measuring the electrical resistance of the toothed belt obtained in the embodiment. [Modes for carrying out the invention]

[0026] <Toothed belt> Below, an example of a toothed belt of the present invention will be described in detail, with reference to the attached drawings as necessary.

[0027] Figure 1 is a schematic partial cross-sectional perspective view showing an example of a toothed belt of the present invention, and Figure 2 is a schematic cross-sectional view of the toothed belt of Figure 1. The toothed belt 1 in this example is an endless interlocking transmission belt, and comprises a back portion 1c in which a core wire 5 extending in the belt circumferential direction (longitudinal direction) is embedded, and a plurality of teeth 1a provided at predetermined intervals on the inner circumferential surface of the back portion 1c and extending in the belt width direction, and the belt surface (inner circumferential surface) on the tooth portion side is made of tooth fabric 2. The back portion 1c has a back rubber layer 6 disposed on the belt outer circumferential surface side of the core wire 5, and this back rubber layer 6 forms the belt outer circumferential surface. Furthermore, the toothed belt 1 of the present invention has a first rubber layer (surface rubber layer) 3 and a second rubber layer (internal rubber layer) 4 between the tooth fabric 2 and the core wire 5 on the belt inner circumferential surface side of the core wire 5. The first rubber layer 3 is disposed on the inner circumferential surface of the belt along the contour of the tooth fabric 2 (in contact with the tooth fabric 2), and the second rubber layer 4 is interposed or disposed between the first rubber layer 3 and the core wire 5 (in contact with the core wire 5).

[0028] Between adjacent tooth portions 1a, there is a flat tooth root portion 1b, and the tooth portions 1a and tooth root portions 1b are alternately formed along the circumferential direction (belt longitudinal direction) on the inner surface of the belt. That is, the surface of the tooth portion 1a and the inner surface of the back portion 1c (i.e., the surface of the tooth root portion 1b) are composed of a single continuous tooth fabric 2.

[0029] In the embodiment shown in Figure 1, the tooth fabric constituting the surface of the tooth portion is a constituent element of the tooth portion, while the tooth fabric constituting the surface of the tooth root portion is a constituent element of the back portion. Furthermore, each tooth fabric constituting the tooth portion is part of a continuous tooth fabric (part of tooth fabric 2 in Figure 2).

[0030] In this example, the tooth portion 1a has a substantially trapezoidal cross-sectional shape in the circumferential direction of the belt. The circumferential surface of the tooth portion 1a, which has a substantially trapezoidal cross-section, is made of the tooth fabric 2, and is formed of a first rubber layer 3 formed along the tooth fabric 2 and a second rubber layer 4 formed between the first rubber layer 3 and the core wire 5. That is, in the tooth portion 1a, the first rubber layer 3 is layered and formed along the tooth fabric 2, and the second rubber layer 4 is layered and formed between the first rubber layer 3 and the core wire 5.

[0031] Furthermore, in the tooth root portion 1b, a first rubber layer acting as a surface rubber layer and a second rubber layer acting as an internal rubber layer are interposed between the tooth fabric 2 and the core wire 5 (not shown). The thickness of the first and second rubber layers in the tooth root portion is extremely thin compared to the thickness of the first rubber layer 3 and the second rubber layer 4 in the tooth portion 1a.

[0032] The core wires 5 extend in the longitudinal direction (circumferential direction) of the belt and are arranged at intervals in the width direction of the belt. The gaps between adjacent core wires 5 may be formed by the cross-linked rubber composition that constitutes the back rubber layer 6 and / or the second rubber layer (in particular, the cross-linked rubber composition that constitutes the back rubber layer 6).

[0033] Toothed belts are used in high-load power transmission applications such as industrial machinery, internal combustion engines in automobiles, and rear-wheel drives in motorcycles. For example, when a toothed belt is wrapped between a drive pulley (toothed pulley) and a driven pulley (toothed pulley), the rotation of the drive pulley transmits power from the drive pulley side to the driven pulley side.

[0034] It should be noted that the toothed belt of the present invention is not limited to the form and structure shown in Figures 1 and 2. For example, the multiple teeth only need to be able to mesh with a toothed pulley, and the cross-sectional shape of the teeth (the cross-sectional shape of the toothed belt in the circumferential direction) is not limited to a substantially trapezoidal shape, but may be, for example, semicircular, semielliptical, polygonal [triangle, quadrilateral (rectangle, trapezoid, etc.)], etc. Of these, a trapezoidal or substantially trapezoidal shape is preferred from the viewpoint of meshing and power transmission.

[0035] Furthermore, in the toothed belts shown in Figures 1 and 2, the surface of the teeth and the surface of the tooth roots, which are the inner circumferential surface of the belt on the tooth side, are made of a single continuous sheet of tooth cloth 2, but the belt may also be configured without tooth cloth. The tooth cloth can be selected according to the requirements for the resistance of the teeth (wear resistance, deformation resistance, etc.), and it is preferable to make the belt surface on the tooth side (inner circumferential surface) of tooth cloth, especially in applications where high loads are applied.

[0036] In the toothed belt of the present invention, the average distance between the centers of adjacent teeth in the circumferential direction (tooth pitch, see Figure 2) may be, for example, 2 to 25 mm, depending on the shape of the toothed pulley. The tooth pitch value corresponds to the size of the tooth scale (length of the tooth in the belt circumferential direction, and tooth height). That is, the larger the tooth pitch, the larger the tooth scale becomes. In particular, in applications where high loads are applied, teeth with a large scale are required, and the tooth pitch may be 5 mm or more, preferably 8 mm or more, and more preferably 14 mm or more.

[0037] Furthermore, the average tooth height of the teeth is, for example, 40-70%, preferably 50-65%, of the average value of the total belt thickness [thickness (distance or height) from the back surface (outer surface) to the tooth crown].

[0038] In this application, as shown in Figure 2, the average tooth height of the teeth refers to the average height of the protruding teeth on the inner surface of the belt [the average value of the thickness (distance or height) from the tooth root surface to the tooth apex].

[0039] [Dental Department] The tooth portion includes a first rubber layer positioned on the surface side (inner surface side) and a second rubber layer positioned on the inner side in contact with the first rubber layer. The first and second rubber layers are formed from crosslinked rubber compositions with different compositions, and the first rubber layer is formed from a rubber composition containing carbon black, with the amount and proportion of DBP absorption of the carbon black being adjusted.

[0040] In this application, the first rubber layer and the second rubber layer, which form the tooth portion, are collectively referred to as the tooth rubber layer. In the tooth rubber layer, the first rubber layer is a single-phase layer formed from the first crosslinked rubber composition, and the second rubber layer is a single-phase layer formed from the second crosslinked rubber composition.

[0041] If the teeth do not include tooth cloth, the rubber layer forming the teeth (tooth rubber layer) refers to the rubber layer interposed on the inner circumferential side relative to the core wire, and the surface of the first rubber layer forms the inner circumferential surface of the belt.

[0042] If the tooth portion includes tooth fabric, the rubber layer forming the tooth portion (tooth rubber layer) refers to the rubber layer interposed between the core wire and the tooth fabric, with the surface of the tooth rubber layer being made of tooth fabric and the inner circumferential surface of the belt being made of tooth fabric. In other words, the tooth portion includes a first rubber layer whose surface is made of tooth fabric and which is positioned along the contour of the tooth portion on the surface side in contact with the tooth fabric, and a second rubber layer positioned on the inner side in contact with the first rubber layer.

[0043] In applications where conductivity is required for toothed belts, conventional techniques have mainly involved imparting conductivity (antistatic properties) to the tooth fabric, which is the outer surface that comes into contact with the pulley, in order to slowly release static electricity to the outside through the pulley and prevent the generation of sparks. However, this method of imparting conductivity to the tooth fabric has the drawbacks of the tooth fabric's adhesion decreasing during operation and the antistatic material (conductive material) being easily lost (worn away). To address these issues, the toothed belt of the present invention has succeeded in solving the problems with the tooth fabric by forming the first rubber layer on the surface side of the teeth, which is formed in a laminated structure, with a first crosslinked rubber composition containing carbon black, and by making the DBP absorption amount and ratio of the carbon black a specific conductive layer (antistatic layer) in which the DBP absorption amount and ratio are adjusted.

[0044] In other words, it was previously thought that when the tooth portion includes a tooth cloth, the tooth rubber layer is not located on the outer surface that contacts the pulley, and therefore static electricity cannot be discharged to the outside through the pulley. However, it was discovered that static electricity can be discharged to the outside even by providing a conductive layer (antistatic layer) on the tooth rubber layer that is not located on the outer surface. Specifically, we succeeded in achieving a high level of conductivity (low electrical resistance) that meets the ISO 9563 (2015) standard.

[0045] Furthermore, in methods that impart conductivity to the outer surface of the tooth fabric, a problem was the decrease in conductivity (increase in electrical resistance) due to the loss (wear) of the conductive material caused by the movement of the belt. However, in the method of providing a conductive layer to the tooth rubber layer, if the tooth portion includes the tooth fabric, the wear of the conductive material is protected by the tooth fabric, and if the tooth portion does not include the tooth fabric, even if the outer surface of the tooth rubber layer wears down, it is supplied from the inside, thus maintaining conductivity (antistatic properties) even while the belt is running.

[0046] Furthermore, in a method where the tooth rubber layer is not divided into two layers, but the entire tooth rubber layer is made a conductive layer (antistatic layer), the tooth rubber layer near the core wire also contains a large amount of carbon black. This reduces the adhesion between the core wire and the tooth rubber layer, and the belt flexibility, which in turn reduces the belt running life. In contrast, as described above, by forming the first rubber layer with the first crosslinked rubber composition, and further forming the second rubber layer with the second crosslinked rubber composition, it becomes possible to impart conductivity (add a large amount of carbon black) only to the side closer to the surface of the teeth, thus ensuring the adhesion between the core wire and the tooth rubber layer, the belt flexibility, and the belt running life.

[0047] As described above, the toothed belt of the present invention is characterized in that, by making the first rubber layer on the surface side of the teeth formed in a laminated structure a specific conductive layer (antistatic layer) made of a first cross-linked rubber composition containing carbon black, it is possible to balance belt flexibility and adhesion and maintain conductivity (antistatic properties) during operation at a high level that passes ISO9563(2015) without reducing the belt's running life and economic efficiency. In particular, if the second rubber layer is formed of a second cross-linked rubber composition with a lower amount of carbon black than the first rubber layer, the belt's running life and economic efficiency can be greatly improved.

[0048] Furthermore, Patent Document 1 also states that carbon black may be incorporated into the tooth rubber layer as a reinforcing inorganic filler. However, Patent Document 1 is characterized by the fact that the amount of carbon black should be kept to a minimum in order to prevent cracking and tooth chipping due to thermal degradation caused by increased heat generation of the rubber composition and reduced heat resistance. In other words, in conventional technologies such as Patent Document 1, the technical significance of incorporating a large amount of carbon black up to the limit of what can be mixed was not envisioned, prioritizing antistatic properties.

[0049] Furthermore, it is preferable that the first rubber layer has a relatively high modulus and the second rubber layer has a relatively low modulus in the teeth. In particular, in applications where high loads are applied to the teeth and a high degree of rigidity (deformation resistance) is required, having such a two-layer structure in the cross-linked rubber composition forming the teeth makes it possible to achieve both the rigidity of the teeth and the flexibility of the belt, which are in a conflicting relationship.

[0050] The shape of the first rubber layer is not particularly limited as long as it is layered along the tooth fabric, and is not limited to the layered shape with uneven thickness shown in Figures 1 and 2 (i.e., in a cross-sectional view of the tooth portion in the longitudinal direction of the belt, the thickness of the layer is maximum at the top or middle of the tooth portion and decreases toward the bottom of the tooth portion), but may also be a layered shape with uniform thickness. Of these, a layered shape with uneven thickness (particularly, in a cross-sectional view of the tooth portion in the longitudinal direction of the belt, the thickness of the layer is maximum at the top or middle of the tooth portion and decreases toward the bottom of the tooth portion) is preferred from the viewpoint of productivity, etc.

[0051] In the tooth portion, the area ratio of the first rubber layer can be selected from a range of approximately 5 to 85 area % of the total area of ​​the first and second rubber layers in a cross-sectional view in the longitudinal direction (circumferential direction) of the belt. For example, 10 to 80 area % is preferred, preferably 10 to 70 area % (particularly 20 to 70 area %), even more preferably 15 to 70 area % (particularly 30 to 60 area %), more preferably 15 to 65 area % (particularly 35 to 50 area %), and most preferably 20 to 60 area %. If this area ratio is too small, there is a risk of insufficient conductivity (antistatic properties), and conversely, if it is too large, the bending rigidity of the belt will increase, resulting in insufficient flexibility (suppleness) and a risk of reduced belt durability. In applications where belt durability is important, the area ratio is preferably 15 to 65 area % and even more preferably 20 to 60 area %.

[0052] The shape of the second rubber layer is not limited to a substantially trapezoidal shape formed between the first rubber layer and the core wire in a cross-sectional view in the longitudinal direction of the belt at the teeth, but may be a layered shape formed along the first rubber layer, or a substantially trapezoidal shape formed between another rubber layer formed along the first rubber layer and the core wire. Of these, a shape in contact with the core wire, i.e., a substantially trapezoidal shape formed between the first rubber layer and the core wire, and a substantially trapezoidal shape formed between the other rubber layer and the core wire are preferred from the viewpoint of improving the flexibility of the belt, and a substantially trapezoidal shape formed between the first rubber layer and the core wire is particularly preferred.

[0053] The tooth portion may further include other rubber layers in addition to the first and second rubber layers, as long as the effects of the present invention are not impaired. Examples of other rubber layers include an adhesive rubber layer interposed between the tooth cloth and the first rubber layer, and an intermediate rubber layer interposed between the first and second rubber layers. The adhesive rubber layer may be a layer for improving the adhesion between the tooth cloth and the first rubber layer. The intermediate rubber layer may be a layer having a smaller tensile modulus than the first rubber layer and a larger tensile modulus than the second rubber layer. Of these, the adhesive rubber layer (third rubber layer) is preferred. The thickness of the adhesive rubber layer should be such that it can improve the adhesion between the tooth cloth and the first rubber layer. Specifically, the thickness of the third rubber layer (adhesive rubber layer) at the top of the tooth portion is preferably 0.5 mm or less, and more preferably 0.3 mm or less. If the thickness of the third rubber layer is too thick, the rigidity of the tooth portion may decrease.

[0054] As for the structure of the teeth, a structure in which the tooth rubber layer includes only an adhesive rubber layer as another layer is preferred, and a structure that does not include any other layers, that is, a structure consisting of a first rubber layer and a second rubber layer formed between the first rubber layer and the core wire, or a structure consisting of a tooth cloth that constitutes the surface in the circumferential direction of the belt, a first rubber layer formed along this tooth cloth, and a second rubber layer formed between the first rubber layer and the core wire is particularly preferred.

[0055] (First crosslinked rubber composition) In the present invention, when the first crosslinked rubber composition forming the first rubber layer contains a first rubber component and a first carbon black, and the DBP absorption amount of the first carbon black is X1 (mL / 100g) and the mass ratio of the first carbon black to 100 parts by mass of the first rubber component is Y1, all of the above requirements 1 to 3 are satisfied, thereby enabling conductivity to be imparted to a toothed belt without reducing the belt's running life and economic efficiency.

[0056] In Requirement 1, the DBP absorption amount X1 of the first carbon black is 110 mL / 100 g or more (particularly 120 mL / 100 g or more), and is not particularly limited as long as it satisfies Requirement 3, but for example it is 115 to 600 mL / 100 g (particularly 120 to 600 mL / 100 g), preferably 130 to 550 mL / 100 g, more preferably 135 to 500 mL / 100 g, and more preferably 135 to 400 mL / 100 g, and non-conductive carbon black Because a large amount of Bond Black can be used, improving cost-effectiveness, and offering an excellent balance of running life, cost-effectiveness, and conductivity, the preferred amount is, for example, 120-300 mL / 100g, preferably 120-200 mL / 100g (e.g., 120-180 mL / 100g), more preferably 130-195 mL / 100g (e.g., 130-170 mL / 100g), more preferably 150-190 mL / 100g, and most preferably 170-185 mL / 100g. If the DBP absorption amount X1 is too low, there is a risk that the conductivity of the toothed belt will decrease.

[0057] In this application, the DBP absorption amount of carbon black refers to the value (OAN) that can be measured for an uncompressible sample, in accordance with JIS K 6217-4 (2017).

[0058] In requirement 2, the proportion Y1 (mass ratio) of the first carbon black is 22 to 88 parts by mass per 100 parts by mass of the first rubber component. It is not particularly limited as long as it satisfies requirement 3, but in order to use a large amount of non-conductive carbon black and improve economic efficiency, for example it is 25 to 85 parts by mass (particularly 77 to 82 parts by mass), preferably 50 to 85 parts by mass, even more preferably 60 to 83 parts by mass (particularly 71 to 83 parts by mass), more preferably 65 to 82 parts by mass (particularly 72 to 82 parts by mass), even more preferably 70 to 80 parts by mass (particularly 73 to 80 parts by mass), and most preferably 72 to 78 parts by mass (particularly 74 to 77 parts by mass). If the mass ratio Y1 is too small, the conductivity of the toothed belt may decrease, and if it is too large, the mixing process of the rubber composition may become difficult, and the productivity of the toothed belt may decrease.

[0059] In requirement 3, the product (X1 × Y1) of the DBP absorption amount X1 and the mass ratio Y1 is 9000 or more (especially 10000 or more), and is not particularly limited as long as it satisfies all requirements 1 to 3, but can be selected from a range of about 9000 to 57000, for example 9300 to 30000 (especially 9500 to 19000), preferably 9500 to 25000 (especially 10000 to 18000), even more preferably 9700 to 20000 (especially 11000 to 16000), more preferably 9900 to 15000 (especially 13000 to 15000), and most preferably 10000 to 14500 (for example 10000 to 12000). If the product (X1 × Y1) is too small, there is a risk that the conductivity of the toothed belt will decrease.

[0060] In this invention, it is sufficient to satisfy requirements 1 to 3. For example, if conductive carbon black has a high DBP absorption rate, high conductivity can be obtained with a small amount of addition, and a level of conductivity (low electrical resistance) that meets ISO 9563 can be obtained. On the other hand, if non-conductive carbon black has a low DBP absorption rate, for example, a large amount can be added to obtain conductivity (low electrical resistance) that meets ISO 9563. In contrast, with carbon black that does not satisfy requirement 1 and has a DBP absorption rate of less than 110 mL / 100 g, adding enough to obtain conductivity (low electrical resistance) exceeds the limit of what can be kneaded and processed, making it impossible to obtain conductivity (low electrical resistance).

[0061] (A) First rubber component Examples of rubber components (first rubber components) of the first crosslinked rubber composition forming the first rubber layer include diene rubbers [natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), chloroprene rubber (CR), butyl rubber (IIR), styrene-butadiene rubber (SBR), vinylpyridine-styrene-butadiene rubber, acrylonitrile-butadiene rubber (nitrile rubber: NBR), acrylonitrile-chloroprene rubber, hydrogenated nitrile rubber (HNBR), etc.], ethylene-α-olefin elastomers (ethylene-propylene copolymer (EPM), ethylene-propylene-diene ternary copolymer (EPDM), etc.), chlorosulfonated polyethylene rubber (CSM), alkylated chlorosulfonated polyethylene rubber (ACSM), epichlorohydrin rubber, acrylic rubber, silicone rubber, urethane rubber, fluororubber, etc. These rubber components may be carboxylated, such as carboxylated SBR and carboxylated NBR. These rubber components can be used individually or in combination of two or more types.

[0062] A particularly preferred first rubber component is hydrogenated nitrile rubber (HNBR), and chloroprene rubber (CR) and ethylene-propylene-diene terpolymer (EPDM) are also suitably used. A particularly preferred rubber component for applications subjected to high loads is a rubber with high heat aging resistance, especially hydrogenated nitrile rubber (HNBR) which may be carboxylated (hereinafter, including carboxylated hydrogenated nitrile rubber, it may simply be referred to as hydrogenated nitrile rubber). The proportion of the above preferred rubber component in the rubber component is preferably 50% by mass or more (for example, about 80-100% by mass), and particularly preferably 100% by mass. The hydrogenated nitrile rubber which may be carboxylated may be partially hydrogenated nitrile rubber or fully hydrogenated nitrile rubber. The hydrogenation rate of the hydrogenated nitrile rubber which may be carboxylated can be selected from a range of about 50-100%, and may be 70-100%.

[0063] In this application, HNBR refers to a rubber that maintains the oil resistance, which is an advantage of conventional nitrile rubber, while preventing the deterioration of rubber elasticity due to sulfur recombination reactions during thermal aging. This is achieved by chemically hydrogenating the unsaturated bonds (carbon-carbon double bonds) present in conventional nitrile rubber, thereby making recombination reactions during thermal aging less likely to occur and improving heat resistance.

[0064] The iodine value (unit: mg / 100 mg) of HNBR is, for example, 5 to 60, preferably 7 to 50, more preferably 8 to 40, more preferably 8 to 35, and most preferably 10 to 30.

[0065] In this application, the iodine value is an indicator of the amount of unsaturated bonds; a higher iodine value indicates a greater amount of unsaturated bonds in the polymer molecular chain. The iodine value is determined by adding an excess of iodine to the sample and allowing it to react completely (reacting with unsaturated bonds), then quantifying the remaining amount of iodine by redox titration. If the iodine value of HNBR is low, the crosslinking reaction between HNBRs is insufficient, resulting in lower rigidity of the crosslinked rubber, which may reduce deformation resistance during belt operation. On the other hand, if the iodine value of HNBR is high, the amount of unsaturated bonds becomes excessively high, which may lead to thermal and oxidative degradation of the crosslinked rubber, shortening the belt life.

[0066] The first rubber component preferably contains at least hydrogenated nitrile rubber, which may be carboxylated. The proportion of such hydrogenated nitrile rubber may be 80 to 100% by mass of the rubber component, preferably 90 to 100% by mass, and more preferably 100% by mass.

[0067] The first rubber component preferably includes a composite polymer containing hydrogenated nitrile rubber and an unsaturated metal carboxylate salt (hereinafter referred to as "HNBR / unsaturated metal carboxylate composite polymer"). This composite polymer may also be a polymer alloy. This polymer can increase the modulus and hardness of the tooth portion.

[0068] An unsaturated carboxylate metal salt may be a compound in which an unsaturated carboxylic acid having one or more carboxyl groups is ionically bonded to a metal.

[0069] Examples of unsaturated carboxylic acids in metal salts of unsaturated carboxylic acids include monocarboxylic acids such as (meth)acrylic acid and crotonic acid, dicarboxylic acids such as maleic acid, fumaric acid and itaconic acid, and monoalkyl esters of these dicarboxylic acids. These unsaturated carboxylic acids can be used alone or in combination of two or more. A preferred unsaturated carboxylic acid is (meth)acrylic acid.

[0070] Examples of metals used in unsaturated carboxylate metal salts include polyvalent metals, such as Group 2 elements of the periodic table (magnesium, calcium, etc.), Group 4 elements (titanium, zirconium, etc.), and Groups 8 to 14 elements of the periodic table (e.g., iron, cobalt, nickel, copper, zinc, aluminum, tin, lead, etc.). These metals can be used individually or in combination of two or more. Preferred metals include Group 2 elements of the periodic table (magnesium, etc.) and Group 12 elements of the periodic table (zinc, etc.).

[0071] Preferred unsaturated carboxylate metal salts include zinc (meth)acrylate and magnesium (meth)acrylate. Unsaturated carboxylate metal salts can be used alone or in combination of two or more.

[0072] Furthermore, commercially available HNBR / unsaturated carboxylate metal salt composite polymers may be used. For example, a product in which zinc methacrylate is highly finely dispersed as an unsaturated carboxylate metal salt in HNBR can be used (e.g., Zeon Corporation's product name "Zeoforte (ZSC)").

[0073] Furthermore, the HNBR / unsaturated carboxylate metal salt composite polymer may be a mixture of a composite polymer in which an unsaturated carboxylate metal salt is finely dispersed in HNBR and hydrogenated nitrile rubber (HNBR) that does not contain an unsaturated carboxylate metal salt. That is, in the HNBR / unsaturated carboxylate metal salt composite polymer, the mass ratio of hydrogenated nitrile rubber to unsaturated carboxylate metal salt may be adjusted by mixing commercially available HNBR containing an unsaturated carboxylate metal salt with commercially available hydrogenated nitrile rubber. The modulus and hardness of the first crosslinked rubber composition may be adjusted by changing the mixing ratio of the two.

[0074] In HNBR / unsaturated carboxylic acid metal salt composite polymers, the mass ratio of hydrogenated nitrile rubber to unsaturated carboxylic acid metal salt can be selected from a range of approximately 100 / 70 to 100 / 180, for example, 100 / 90 to 100 / 170, preferably 100 / 95 to 100 / 150, and more preferably 100 / 100 to 100 / 120. If the proportion of unsaturated carboxylic acid metal salt is too low, the modulus and hardness of the crosslinked rubber composition (or teeth) may decrease, while if it is too high, the processability and flexibility of the belt may decrease.

[0075] The proportion of HNBR / unsaturated carboxylate metal salt composite polymer may be 10% by mass or more in the first rubber component, preferably 30% by mass or more, more preferably 50% by mass or more, more preferably 80% by mass or more, most preferably 90% by mass or more, and may also be 100% by mass. These proportions may be those used in the product "Zeoforte (ZSC)".

[0076] As other rubber components to be combined with the HNBR / unsaturated carboxylic acid metal salt composite polymer, at least one selected from the group consisting of EPDM and CR is preferred. The proportion of the other rubber components is, for example, 70% by mass or less, preferably 50% by mass or less, more preferably 30% by mass or less, and most preferably 10% by mass or less, in the first rubber component.

[0077] The proportion of the first rubber component may be 10 to 90% by mass in the first crosslinked rubber composition, preferably 20 to 80% by mass, more preferably 25 to 70% by mass, more preferably 30 to 60% by mass, and most preferably 40 to 50% by mass.

[0078] (B) Carbon Black No. 1 The first carbon black is not particularly limited as long as it satisfies the DBP absorption amount X1, and may be a non-conductive carbon black such as furnace black, or a conductive carbon black such as thermal black, Ketjen black, acetylene black, channel black, or color black. Of these, non-conductive carbon black is preferred due to its high economic efficiency, and conductive carbon black is preferred because it can impart conductivity with a small amount of addition and easily improves the belt's running life.

[0079] The average particle size (average primary particle size) of the first carbon black is, for example, 1 to 200 nm, preferably 3 to 150 nm, more preferably 5 to 100 nm, more preferably 10 to 50 nm, even more preferably 15 to 40 nm, and most preferably 20 to 30 nm.

[0080] In this application, the average primary particle size of carbon black can be measured using a transmission electron microscope as the arithmetic mean particle size of an appropriate number of samples (e.g., 50 samples).

[0081] (C) First filling system compounding agent The first crosslinked rubber composition may further contain a first filler compound. Examples of the first filler compound include a first filler and first short fibers.

[0082] Examples of first fillers include polyvalent metal carbonates (calcium carbonate, magnesium carbonate, etc.), polyvalent metal hydroxides (aluminum hydroxide, etc.), polyvalent metal sulfates (barium sulfate, etc.), silicates (natural or synthetic silicates in which some of the silicon atoms are replaced by polyvalent metal atoms, such as aluminum silicate, magnesium silicate, and aluminum magnesium silicate; minerals with silicates as the main component, such as clay containing aluminum silicate, and silicate minerals such as talc and mica containing magnesium silicate), silica, lithopone, and silica sand. These fillers can be used alone or in combination of two or more.

[0083] Of these, it is preferable to include at least one selected from calcium carbonate, magnesium silicate or talc containing magnesium silicate, aluminum silicate or clay containing aluminum silicate, and it is particularly preferable to include calcium carbonate. As the first filler, commercially available powdered fillers used as rubber fillers can be used.

[0084] The average particle size (average primary particle size) of the first filler can be selected from a range of approximately 0.01 to 25 μm (e.g., 0.2 to 20 μm), preferably 0.5 to 17 μm (e.g., 1 to 15 μm). The average particle size (average primary particle size) of the first filler may also be, for example, 0.2 to 5 μm (e.g., 0.3 to 3 μm), preferably 0.5 to 2.5 μm (particularly 1 to 2 μm). Depending on the type of first filler, such as magnesium silicate or its minerals, the first filler may be crushed or broken during the mixing process with rubber components. The average particle size of such a crushable or breakable first filler may be the average particle size before mixing with rubber components.

[0085] In this application, the average particle diameter of the first filler can be measured as the volume-average particle diameter using a laser diffraction particle size distribution analyzer. Furthermore, the average particle diameter of the nanometer-sized first filler can be calculated as the arithmetic mean particle diameter of an appropriate number of samples (e.g., 50 samples) by image analysis of electron microscope images, including scanning electron microscope images.

[0086] The proportion of the first filler is, for example, 70 parts by mass or less, preferably 40 parts by mass or less, and more preferably 30 parts by mass or less, per 100 parts by mass of the first rubber component. If the first filler is used as needed, the proportion of the first filler is, for example, 3 to 50 parts by mass, preferably 5 to 30 parts by mass, and more preferably 8 to 25 parts by mass, per 100 parts by mass of the first rubber component. If the proportion of the first filler is too high, the dispersibility of the compounding agent may be poor.

[0087] The first short fibers can be oriented (arranged) in a predetermined direction during the process of preparing an uncrosslinked rubber sheet by rolling a rubber composition, which has been kneaded in a Banbury mixer or the like, using a roll or calender. In the tooth rubber layer that constitutes the teeth, it is preferable to arrange the orientation of the first short fibers toward the belt circumferential direction. Furthermore, it is preferable that the first short fibers are oriented along the contour of the teeth on the side closer to the tooth fabric, and as they approach the core wire, the first short fibers are oriented so that they are almost parallel to the core wire.

[0088] In this application, the state in which the first short fibers are oriented along the contour of the tooth means not only the state in which the first short fibers are oriented substantially parallel to the contour of the tooth, but also the state in which the first short fibers are oriented substantially parallel to the contour of the tooth fabric (or inner surface). The same applies to the state in which the first short fibers are oriented in the longitudinal direction of the belt.

[0089] Furthermore, in this application, the "tooth contour" may be the contour of the first rubber layer, or if the tooth includes a tooth cloth, it may be the tooth cloth surface or the interface between the tooth cloth and the first rubber layer, or it may be the interface between the first rubber layer and the second rubber layer. In particular, whether or not the first short fibers are oriented along the contour of the tooth may be determined based on the interface between the first rubber layer and the second rubber layer. For example, if the first short fibers are substantially parallel to the corresponding interface (the corresponding part of the interface at the shortest distance from the first short fibers), it may be determined that they are oriented along the contour of the tooth.

[0090] Examples of first staple fibers include polyolefin fibers (polyethylene fibers, polypropylene fibers, etc.), polyamide fibers [aliphatic polyamide fibers such as polyamide 6 fibers, polyamide 66 fibers, polyamide 46 fibers (nylon fibers), aramid fibers, etc.], polyester fibers [polyalkylene arylate fibers (e.g., polyethylene terephthalate (PET) fibers, polytrimethylene terephthalate (PTT) fibers, polybutylene terephthalate (PBT) fibers, polyethylene naphthalate (PEN) fibers, etc.)] 2-4 Alkilen C 8-14 Examples of synthetic fibers include: arylate fibers; polyarylate fibers, fully aromatic polyester fibers such as liquid crystal polyester fibers, etc.; vinylon fibers, polyvinyl alcohol fibers, poly-p-phenylenebenzobisoxazole (PBO) fibers; natural fibers such as cotton, linen, and wool; regenerated cellulose fibers such as rayon; cellulose ester fibers, etc.; and inorganic fibers such as carbon fibers and glass fibers. These short fibers can be used individually or in combination of two or more types. In particular, fibers with high modulus, such as polyamide fibers, PBO fibers, glass fibers, and carbon fibers, can be suitably used, with polyamide fibers such as aliphatic polyamide fibers (nylon fibers) and aramid fibers, and PBO fibers being more preferred, and aliphatic polyamide fibers being the most preferred.

[0091] The average fiber diameter of the first short fibers is, for example, 1 to 100 μm, preferably 3 to 70 μm, more preferably 5 to 50 μm, and more preferably 10 to 30 μm. The average fiber length of the short fibers is, for example, 0.3 to 10 mm, preferably 0.5 to 7 mm, more preferably 1 to 5 mm, and more preferably 2 to 4 mm. If the average fiber diameter of the first short fibers is too small or the average fiber length is too long, there is a risk that the first short fibers will not be able to be dispersed uniformly, and if the average fiber diameter is too large or the average fiber length is too short, there is a risk that the strength of each rubber layer will decrease.

[0092] The proportion of the first short fibers may be 60 parts by mass or less per 100 parts by mass of the first rubber component, and can be selected from a range of about 0 to 50 parts by mass depending on the application. The proportion of the first short fibers can be selected depending on the application, for example, in applications where high load (high horsepower) is required, it may be, for example, 5 to 60 parts by mass, preferably 10 to 55 parts by mass, more preferably 15 to 45 parts by mass, more preferably 20 to 40 parts by mass, and most preferably 25 to 35 parts by mass per 100 parts by mass of the first rubber component. In applications where low load is required, the proportion of the first short fibers may be 10 parts by mass or less, preferably 7 parts by mass or less, and more preferably 5 parts by mass or less per 100 parts by mass of the first rubber component.

[0093] Furthermore, it is preferable to subject the first short fibers to a conventional adhesive treatment (or surface treatment) to adhere an adhesive component to at least a portion of the surface of the short fibers. Examples of adhesive treatments include treatment with adhesive components such as epoxy compounds (or epoxy resins), polyisocyanates, silane coupling agents, and RFL liquid.

[0094] The proportion of the first filler compound is, for example, 10 to 100 parts by mass, preferably 20 to 80 parts by mass, more preferably 30 to 70 parts by mass, and more preferably 40 to 60 parts by mass, per 100 parts by mass of the first rubber component.

[0095] (D) First cross-linking compound The first crosslinked rubber composition may further contain a first crosslinking compound. Examples of the first crosslinking compound include a first crosslinking agent (vulcanizing agent) for crosslinking the first rubber component, as well as a first co-crosslinking agent, a first crosslinking aid (vulcanization aid), a first crosslinking accelerator (vulcanization accelerator), and a first crosslinking retarder (vulcanization retarder). Of these, the first crosslinking compound preferably contains at least a first crosslinking agent and a first co-crosslinking agent (crosslinking aid), and a combination of a first crosslinking agent and a first co-crosslinking agent is particularly preferred.

[0096] As the first crosslinking agent, conventional components can be used depending on the type of first rubber component, and examples include organic peroxides, sulfur-based crosslinking agents, and metal oxides.

[0097] Examples of organic peroxides include di-t-butyl peroxide, dicumyl peroxide, t-butylcumyl peroxide, 1,1-t-butylperoxy-3,3,5-trimethylcyclohexane, 1,3-bis(t-butylperoxyisopropyl)benzene, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyn-3, 1,3-bis(t-butylperoxy-di-isopropyl)benzene, 2,5-di-methyl-2,5-di(benzoylperoxy)hexane, t-butylperoxybenzoate, and t-butylperoxy-2-ethyl-hexyl carbonate. These organic peroxides can be used individually or in combination of two or more.

[0098] Examples of sulfur-based crosslinking agents include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, and sulfur chloride (sulfur monochloride, sulfur dichloride, etc.). These sulfur-based crosslinking agents can be used individually or in combination of two or more.

[0099] Examples of metal oxides include magnesium oxide, zinc oxide, and lead oxide. These metal oxides can be used individually or in combination of two or more.

[0100] The first crosslinking agent can be appropriately selected depending on the type of the first rubber component, and organic peroxides and metal oxides are preferred, with organic peroxides being particularly preferred. The first crosslinking agent may also be a combination of organic peroxides and metal oxides.

[0101] The proportion of the first crosslinking agent is, for example, 1 to 20 parts by mass, preferably 3 to 15 parts by mass, and more preferably 5 to 10 parts by mass, per 100 parts by mass of the first rubber component. If the proportion of the first crosslinking agent is too low, the modulus and hardness of the first crosslinked rubber composition will decrease, while if it is too high, the flexibility of the belt will decrease.

[0102] The proportion of organic peroxide can be selected from a range of about 0.5 to 20 parts by mass per 100 parts by mass of the first rubber component, for example, 0.5 to 10 parts by mass, preferably 0.7 to 5 parts by mass, more preferably 0.8 to 4 parts by mass, and even more preferably 1 to 3 parts by mass.

[0103] The proportion of the metal oxide is, for example, 0.1 to 30 parts by mass, preferably 0.5 to 20 parts by mass, more preferably 1 to 15 parts by mass, more preferably 2 to 10 parts by mass, and most preferably 3 to 7 parts by mass, per 100 parts by mass of the first rubber component.

[0104] The first co-crosslinking agent (crosslinking aid or co-vulcanizing agent) is a known crosslinking aid, for example, polyfunctional (iso)cyanurates [e.g., triallyl isocyanurate (TAIC), triallyl cyanurate (TAC), etc.], polydienes (e.g., 1,2-polybutadiene, etc.), metal salts of unsaturated carboxylic acids [e.g., polyvalent metal salts of (meth)acrylic acids such as zinc (meth)acrylate and magnesium (meth)acrylate], oximes (e.g., quinone dioxime, etc.), guanidines (e.g., diphenylguanidine, etc.), polyfunctional (meth)acrylates [e.g., ethylene glycol di(meth)acrylate, alkanediol di(meth)acrylate such as butanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetraacrylate, etc.]. Examples include alkane polyol poly(meth)acrylates such as tra(meth)acrylate, bismaleimides (aliphatic bismaleimides, e.g., alkylene bismaleimides such as N,N'-1,2-ethylenedimaleimide, N,N'-hexamethylenebismaleimide, 1,6'-bismaleimide-(2,2,4-trimethyl)cyclohexane; arene bismaleimides or aromatic bismaleimides, e.g., N,N'-m-phenylenedimaleimide, 4-methyl-1,3-phenylenedimaleimide, 4,4'-diphenylmethanedimaleimide, 2,2-bis[4-(4-maleimoidphenoxy)phenyl]propane, 4,4'-diphenyletherdimaleimide, 4,4'-diphenylsulfonedimaleimide, 1,3-bis(3-maleimoidphenoxy)benzene, etc.). These cocrosslinking agents can be used alone or in combination of two or more. Among these co-crosslinking agents, polyfunctional (iso)cyanurates, polyfunctional (meth)acrylates, and bismaleimides (arene bismaleimides such as N,N'-m-phenylenedimaleimide or aromatic bismaleimides) are preferred, with bismaleimides being particularly preferred. The degree of crosslinking and the modulus of elasticity can be improved by adding a co-crosslinking agent (e.g., bismaleimides).

[0105] The proportion of the first co-crosslinking agent (crosslinking aid), such as bismaleimides, can be selected from a range of approximately 0.2 to 40 parts by mass per 100 parts by mass of the first rubber component, based on solid content. For example, it is 0.3 to 30 parts by mass, preferably 0.5 to 20 parts by mass, more preferably 0.8 to 15 parts by mass, and more preferably 1 to 10 parts by mass. In applications requiring high load (high horsepower), the proportion of the first co-crosslinking agent may be, based on solid content, for example, 1 to 40 parts by mass, preferably 2 to 30 parts by mass (e.g., 5 to 20 parts by mass), more preferably 2.5 to 18 parts by mass (e.g., 8 to 15 parts by mass), more preferably 3 to 14 parts by mass (e.g., 4 to 12 parts by mass), and most preferably 6 to 11 parts by mass (e.g., 5 to 7 parts by mass), per 100 parts by mass of the first rubber component.

[0106] The proportion of the first crosslinking compound can be selected from a range of about 1 to 50 parts by mass per 100 parts by mass of the first rubber component, based on solid content, for example, 2 to 30 parts by mass, preferably 3 to 25 parts by mass, more preferably 5 to 20 parts by mass, and more preferably 7 to 10 parts by mass.

[0107] (E) 1 Other Combination Agents The first crosslinked rubber composition may further contain conventional additives used in rubber compositions for toothed belts. Commonly used additives include, for example, metal oxides (calcium oxide, barium oxide, iron oxide, copper oxide, titanium oxide, aluminum oxide, etc.), softeners (oils such as paraffin oil and naphthenic oils), processing agents or processing aids (stearic acid or its metal salts, waxes, paraffin, fatty acid amides, etc.), plasticizers [aliphatic carboxylic acid plasticizers (adipate ester plasticizers, sebacate ester plasticizers, etc.), aromatic carboxylic acid ester plasticizers (phthalate ester plasticizers, trimellitic acid ester plasticizers, etc.), oxycarboxylic acid ester plasticizers, phosphate ester plasticizers, ether plasticizers, ether ester plasticizers, etc.], antioxidants (antioxidants, heat aging inhibitors, flex crack inhibitors, ozone degradation inhibitors, etc.), colorants, tackifiers, plasticizers, coupling agents (silane coupling agents, etc.), stabilizers (ultraviolet absorbers, heat stabilizers, etc.), flame retardants, and antistatic agents. Furthermore, the crosslinked rubber composition may optionally contain adhesion improvers (such as resorcinol-formaldehyde cocondensates or amino resins). These additives can be used individually or in combination of two or more.

[0108] In particular, the proportion of the processing agent or processing aid is, for example, 0.1 to 5 parts by mass, preferably 0.2 to 3 parts by mass, and more preferably 0.3 to 1 part by mass, per 100 parts by mass of the first rubber component.

[0109] The proportion of the anti-aging agent is, for example, 0.1 to 10 parts by mass, preferably 0.5 to 5 parts by mass, and more preferably 1 to 3 parts by mass, per 100 parts by mass of the first rubber component.

[0110] The total proportion of the first other compounding agent is, for example, 0.1 to 30 parts by mass, preferably 0.5 to 20 parts by mass, and more preferably 1 to 10 parts by mass, per 100 parts by mass of the first rubber component.

[0111] (Second crosslinked rubber composition) In the present invention, the second crosslinked rubber composition forming the second rubber layer is not particularly limited as long as it contains a second rubber component and does not satisfy any of requirements 1 to 3 of the first crosslinked rubber composition. However, a crosslinked rubber composition that does not contain second carbon black or has a low proportion of second carbon black is preferred in order to improve the belt's running life.

[0112] Regarding requirement 1 for the first crosslinked rubber component, in the second crosslinked rubber composition, the proportion of the second carbon black (mass ratio Y2, which is the parts by mass of the second carbon black per 100 parts by mass of the second rubber component) may be less than 35 parts by mass per 100 parts by mass of the second rubber component, preferably less than 22 parts by mass, more preferably 15 parts by mass or less (particularly 10 parts by mass or less), more preferably 5 parts by mass or less, and most preferably 3 parts by mass or less. If the proportion of the second carbon black is too high, the belt's running life may decrease.

[0113] When the second crosslinked rubber composition contains a second carbon black, the proportion of the second carbon black is, for example, 0.1 parts by mass or more and less than 35 parts by mass (particularly 0.1 parts by mass or more and less than 18 parts by mass), preferably 0.2 parts by mass or more and less than 22 parts by mass (particularly 0.2 to 15 parts by mass), more preferably 0.3 parts by mass or more and less than 22 parts by mass (particularly 0.3 to 10 parts by mass), more preferably 0.5 parts by mass or more and less than 22 parts by mass (particularly 0.5 to 5 parts by mass), and most preferably 1 part by mass or more and less than 22 parts by mass (particularly 1 to 3 parts by mass), based on 100 parts by mass of the second rubber component. If the proportion of the second carbon black is too low, the strength of the belt may decrease, so it is particularly preferable that the second crosslinked rubber composition contains a small amount of the second carbon black.

[0114] With respect to requirement 2 above, the DBP absorption amount X2 of the second carbon black may be less than 150 mL / 100 g (especially less than 120 mL / 100 g) from the standpoint of economics, etc., for example, 30 mL / 100 g or more and less than 150 mL / 100 g (especially 30 mL / 100 g or more and less than 120 mL / 100 g), preferably 50 mL / 100 g or more and less than 150 mL / 100 g (especially 50 to 100 mL / 100 g), and even more preferably 60 mL / 100 g or more and less than 150 mL / 100 g (especially 60 to 80 mL / 100 g).

[0115] With respect to requirement 3, the product of the DBP absorption amount X2 and the mass ratio Y2 (X2 × Y2) may be less than 9000, for example, 0 to 5000, preferably 1 to 3000, more preferably 10 to 3000 (especially 10 to 1000), more preferably 30 to 3000 (especially 30 to 500), and most preferably 50 to 3000 (especially 50 to 200). If the product (X2 × Y2) is too large, the running life of the toothed belt may decrease.

[0116] In this invention, by combining a second rubber layer formed from a second crosslinked rubber composition that does not satisfy at least one of requirements 1 to 3 with a first rubber layer formed from a first crosslinked rubber composition that satisfies requirements 1 to 3, it is possible to achieve both the conductivity and running life of a toothed belt, which are in a trade-off relationship.

[0117] (A) Second rubber component The second rubber component of the second crosslinked rubber composition forming the second rubber layer can be selected from the rubber components exemplified as the first rubber component, including preferred embodiments. The second rubber component is preferably of the same series or type as the first rubber component, and more preferably of the same type, in order to improve interlayer adhesion.

[0118] In the second rubber component, in the HNBR / unsaturated carboxylic acid metal salt composite polymer, the mass ratio of hydrogenated nitrile rubber to unsaturated carboxylic acid metal salt is former / latter = 100 / 70 to 100 / 110, preferably 100 / 75 to 100 / 100, and more preferably 100 / 80 to 100 / 90. If the proportion of unsaturated carboxylic acid metal salt is too low, the modulus and hardness of the crosslinked rubber composition (or teeth) may decrease, while if it is too high, the processability and flexibility of the belt will decrease.

[0119] The proportion of the second rubber component may be 10 to 95% by mass in the second crosslinked rubber composition, preferably 30 to 93% by mass, more preferably 50 to 90% by mass, more preferably 60 to 85% by mass, and most preferably 70 to 80% by mass.

[0120] (B) Second Carbon Black The second carbon black is not particularly limited and may be conductive carbon black such as thermal black, Ketjen black, acetylene black, channel black, or color black, but non-conductive carbon black such as furnace black is preferred from the standpoint of economy and other factors.

[0121] The average particle size (average primary particle size) of the second carbon black is, for example, 1 to 200 nm, preferably 5 to 150 nm, more preferably 10 to 100 nm, more preferably 30 to 90 nm, even more preferably 50 to 80 nm, and most preferably 60 to 70 nm.

[0122] (C) Second filling system compounding agent The second crosslinked rubber composition may further contain a second filler compound. Examples of the second filler compound include a second filler and second short fibers.

[0123] The second filler can be selected from the fillers exemplified as the first filler, including preferred embodiments.

[0124] The range of the average particle diameter (average primary particle diameter) and the ratio of the second filler to the second rubber component can be selected from the range described as the average particle diameter and the ratio of the first filler to the first rubber component, including preferred ranges.

[0125] The second short fiber can be selected from the short fibers exemplified as the first short fiber. The short fibers can be used alone or in combination of two or more types. Among the short fibers, the second short fiber can preferably be a polyamide fiber, PBO fiber, glass fiber, carbon fiber, or other fiber with a high modulus of elasticity. Polyamide fibers such as aliphatic polyamide fibers (nylon fibers) and aramid fibers, and PBO fibers are more preferred, with aramid fibers being the most preferred.

[0126] The proportion of the second short fibers may be 50 parts by mass or less per 100 parts by mass of the second rubber component, for example, 0.1 to 50 parts by mass, preferably 0.2 to 30 parts by mass, more preferably 0.3 to 10 parts by mass, more preferably 0.5 to 5 parts by mass, and most preferably 1 to 3 parts by mass.

[0127] The second short fiber may also be subjected to conventional bonding treatment, similar to the first short fiber.

[0128] The proportion of the second filling compound is, for example, 5 to 100 parts by mass, preferably 10 to 50 parts by mass, more preferably 15 to 40 parts by mass, and more preferably 20 to 30 parts by mass, per 100 parts by mass of the second rubber component.

[0129] (D) Second crosslinking compound The second crosslinked rubber composition may further contain a second crosslinking compound. Examples of second crosslinking compounds include a second crosslinking agent (vulcanizing agent) for crosslinking the second rubber component, as well as a second cocrosslinking agent, a second crosslinking aid (vulcanization aid), a second crosslinking accelerator (vulcanization accelerator), and a second crosslinking retarder (vulcanization retarder). Of these, the second crosslinking compound preferably contains at least a second crosslinking agent and a second cocrosslinking agent (crosslinking aid), and a combination of a second crosslinking agent and a second cocrosslinking agent is particularly preferred.

[0130] The second crosslinking agent can be selected from the crosslinking agents exemplified as the first crosslinking agent, including preferred embodiments. The range of the ratio of the second crosslinking agent to the second rubber component can be selected from the range described as the ratio of the first crosslinking agent to the first rubber component, including preferred ranges.

[0131] The second cocrosslinking agent can be selected from the cocrosslinking agents exemplified as the first cocrosslinking agent, including preferred embodiments.

[0132] The proportion of the second cocrosslinking agent is, for example, 0.2 to 25 parts by mass, preferably 0.5 to 10 parts by mass, more preferably 0.7 to 7 parts by mass (for example 0.8 to 5 parts by mass), more preferably 0.8 to 4 parts by mass (for example 0.8 to 3 parts by mass), and most preferably 0.8 to 2 parts by mass, per 100 parts by mass of the second rubber component.

[0133] The range of the ratio of the second crosslinking compound to the second rubber component can be selected from the range described as the ratio of the first crosslinking compound to the first rubber component, including preferred ranges.

[0134] (E) Second Other Combination Agent The second crosslinked rubber composition may further contain conventional additives used in rubber compositions for toothed belts. These conventional additives can be selected from those exemplified as the first other compounding agents, including preferred embodiments.

[0135] In particular, the proportion of the processing agent or processing aid is, for example, 0.1 to 5 parts by mass, preferably 0.2 to 3 parts by mass, and more preferably 0.3 to 1 part by mass, per 100 parts by mass of the second rubber component.

[0136] The proportion of the anti-aging agent is, for example, 0.1 to 5 parts by mass, preferably 0.3 to 2 parts by mass, and more preferably 0.5 to 1.5 parts by mass, per 100 parts by mass of the second rubber component.

[0137] The total proportion of the second other compounding agent is, for example, 0.1 to 30 parts by mass, preferably 0.5 to 20 parts by mass, and more preferably 1 to 10 parts by mass, per 100 parts by mass of the second rubber component.

[0138] (Tooth cloth) If the teeth include a tooth fabric, the tooth fabric constituting the inner circumferential surface of the belt (the surface of the teeth and tooth base) may be made of a fabric such as a woven fabric, knitted fabric, or nonwoven fabric. Conventionally, it is often a woven fabric (canvas), and is composed of a fabric woven from warp threads extending in the belt width direction and weft threads extending in the belt circumference direction. The weave structure of the woven fabric is not particularly limited as long as the warp and weft threads intersect regularly in the vertical and horizontal directions, and may be any of plain weave, twill weave (or diagonal weave), satin weave, or a weave structure that combines these structures. Preferred woven fabrics have a twill weave and a satin weave structure.

[0139] In addition to the fibers exemplified as the first short fibers, examples of fibers forming the weft and warp threads of the tooth fabric include polyphenylene ether fibers, polyether ether ketone fibers, polyether sulfone fibers, and polyurethane fibers. These fibers can be used individually or in combination of two or more. Among these fibers, organic fibers are commonly used, with cellulose fibers such as cotton and rayon, polyester fibers (such as PET fibers), polyamide fibers (such as aliphatic polyamide fibers like polyamide 66 fibers, aramid fibers, etc.), PBO fibers, and fluororesin fibers [such as polytetrafluoroethylene (PTFE) fibers] being preferred. Furthermore, composite yarns of these fibers and elastic yarns with elasticity (for example, polyurethane elastic yarns with elasticity such as spandex made of polyurethane, and processed yarns that have undergone stretch processing (for example, woolly processing, crimping processing, etc.)) are also preferred.

[0140] The form of the warp and weft threads is not particularly limited and may be monofilament yarn, which is a single long fiber; multifilament yarn, which is made by aligning or twisting filaments (long fibers); or spun yarn, which is made by twisting short fibers. The multifilament yarn or spun yarn may be a blended yarn or blended yarn using multiple types of fibers. The weft threads preferably contain elastic yarn, while the warp threads usually do not contain elastic yarn from the viewpoint of weaving. In order to ensure the elasticity of the tooth fabric in the circumferential direction of the belt, the weft threads containing elastic yarn extend in the circumferential direction of the belt, and the warp threads extend in the width direction of the belt.

[0141] The average diameter of the fibers (or yarn) is, for example, 1 to 100 μm (e.g., 3 to 50 μm), preferably 5 to 30 μm, and more preferably 7 to 25 μm. Regarding the average fiber diameter (thickness) of the yarn (twisted yarn), the weft may be, for example, 100 to 1000 dtex (particularly 300 to 700 dtex), and the warp may be, for example, 50 to 500 dtex (particularly 100 to 300 dtex). The density of the weft (threads / cm) may be, for example, 5 to 50 (particularly 10 to 30), and the density of the warp (threads / cm) may be, for example, 10 to 300 (particularly 20 to 100).

[0142] The woven fabric may have a multi-layered structure (such as a double-layered structure), and in a woven structure comprising warp and weft threads, at least some of the weft threads may be made of low-friction fibers (or low-friction fibers) such as fluororesin-containing fibers (such as composite yarns containing fibers formed from fluororesins such as PTFE). For example, the warp threads may be made of polyamide fibers such as nylon 66, polyester fibers, etc., and the weft threads may be made of fluororesin-formed fibers alone; composite yarns of fluororesin-formed fibers and second fibers such as polyamide fibers or polyurethane fibers (elastic yarns); or composite yarns of this composite yarn and a second composite yarn formed from a plurality of the second fibers.

[0143] In a woven fabric having a multi-layered structure, it is preferable to use a fluorine-based fiber (e.g., PTFE fiber) with a low coefficient of friction as the weft thread located on the surface side of the toothed fabric (the side that engages with the toothed pulley) (exposed side) in order to reduce friction between the toothed fabric and the toothed pulley. On the other hand, by using a fiber other than a fluorine-based fiber for the weft thread located on the back side of the toothed fabric (the side that adheres to the first rubber layer), it is possible to increase the adhesive strength between the toothed fabric and the rubber constituting the teeth. In this embodiment of the toothed fabric, friction during engagement between the toothed fabric and the toothed pulley can be reduced.

[0144] Furthermore, when using fluorine-based fibers, it is preferable that low-melting-point fibers having a melting point that melts at the crosslinking (vulcanization) temperature of the teeth and back, which are based on rubber, are arranged around the fluorine-based fibers. Specifically, the form of the composite yarn containing fluorine-based fibers includes forms in which fluorine-based fibers and low-melting-point fibers are mixed and twisted together, or forms in which fluorine-based fibers are covered by low-melting-point fibers. The crosslinking (vulcanization) conditions of the teeth and back are not particularly limited, but generally, the crosslinking (vulcanization) temperature is 100 to 200°C and the crosslinking (vulcanization) time is 1 minute to 5 hours.

[0145] In an embodiment in which low-melting-point fibers are arranged around fluorine-based fibers, the low-melting-point fibers melt during cross-linking (vulcanization) of the teeth and back portions, flow into the spaces between the fibers constituting the tooth fabric, and then crystallize when cooled to below their melting point. Therefore, the cutting and scattering of fluorine-based fibers due to impact and abrasion on the surface of the tooth fabric during engagement with or disengagement from a toothed pulley is suppressed.

[0146] The average thickness of the tooth fabric (the tooth fabric in the toothed belt) is, for example, 0.1 to 2 mm, preferably 0.2 to 1.5 mm. The average thickness of the tooth fabric as raw material (the tooth fabric before molding) is, for example, 0.5 to 3 mm, preferably 0.75 to 2.5 mm.

[0147] To improve adhesion with the first rubber layer, the fabric forming the tooth cloth may be subjected to an adhesive treatment. Examples of adhesive treatments include immersing the fabric in an RFL treatment solution followed by heat drying; treating with an epoxy compound or isocyanate compound; and dissolving a rubber composition in an organic solvent to make rubber glue, immersing the fabric in this rubber glue, and then heat drying. These methods can be performed individually or in combination, and the order and number of treatments are not limited. For example, after immersing in the RFL treatment solution, the fabric may be further immersed in rubber glue and then heat dried.

[0148] Furthermore, in order to improve the adhesion between the tooth cloth and the first rubber layer, an uncrosslinked rubber sheet, formed by rolling a rubber composition, may be laminated on the back surface (the side that adheres to the first rubber layer) of the fabric forming the tooth cloth. This rubber composition (third crosslinked rubber composition) can be appropriately selected from the crosslinked rubber compositions exemplified above as the crosslinked rubber compositions forming the first rubber layer, and may also be a conventional adhesive rubber composition. In addition, the uncrosslinked rubber sheet made of this rubber composition may form a third rubber layer (adhesive rubber layer) interposed between the tooth cloth and the first rubber layer in a toothed belt. The fabric subjected to the above adhesive treatment will be referred to as the tooth cloth precursor.

[0149] [Tooth root] When the tooth portion includes a tooth cloth, the tooth cloth constitutes the surface of the tooth portion, as well as the surface on the tooth side of the back (the surface of the tooth root).

[0150] When the tooth portion includes a tooth cloth, in the dorsal portion corresponding to the tooth root, a first rubber layer and a second rubber layer may be interposed between the tooth cloth and the core wire, but only the first rubber layer may be interposed, or the tooth cloth and the core wire may be in contact without the first and second rubber layers interposed. In the dorsal portion corresponding to the tooth root, whether the first rubber layer is interposed or both the first and second rubber layers are interposed, the thickness of the first rubber layer, and the thickness of the first and second rubber layers, are always formed to be thinner than that of the tooth portion.

[0151] If the tooth portion does not include tooth cloth, the dorsal portion corresponding to the tooth root may be formed of a first rubber layer and a second rubber layer, or it may be formed of the first rubber layer alone. In the dorsal portion corresponding to the tooth root, the thickness of the first rubber layer, and the thicknesses of the first and second rubber layers are formed to be thinner than those of the tooth portion in all cases.

[0152] [Back rubber layer] The back portion has the teeth and tooth roots formed on its inner circumferential surface, and on its outer circumferential surface, it has a back rubber layer that forms the outer circumferential surface of the belt. Furthermore, the back rubber layer is made of a crosslinked rubber composition (fourth crosslinked rubber composition). In the embodiments of Figures 1 and 2, the other surface (back of the belt) on the side where the teeth are not formed is not made of fabric (woven fabric, knitted fabric, nonwoven fabric, etc.), but may be made of fabric as needed. This fabric can be selected from the fabrics exemplified as tooth fabrics, including preferred embodiments.

[0153] (Fourth crosslinked rubber composition) The fourth crosslinked rubber composition forming the back rubber layer is not particularly limited as long as it contains a fourth rubber component and does not impair the adhesion between the back rubber layer and the teeth.

[0154] (A) Fourth rubber component The fourth rubber component can be selected from the rubber components exemplified as the first rubber component, including preferred embodiments. The fourth rubber component is preferably of the same series or type as the second rubber component, and more preferably of the same type, in order to improve adhesion with the tooth.

[0155] Furthermore, in the fourth rubber component, in the HNBR / unsaturated carboxylic acid metal salt composite polymer, the mass ratio of hydrogenated nitrile rubber to unsaturated carboxylic acid metal salt is former / latter = 100 / 1 to 100 / 50, preferably 100 / 3 to 100 / 30, and more preferably 100 / 5 to 100 / 20.

[0156] The proportion of the fourth rubber component may be 10 to 95% by mass in the second crosslinked rubber composition, preferably 30 to 93% by mass, more preferably 50 to 90% by mass, more preferably 50 to 80% by mass, and most preferably 60 to 70% by mass.

[0157] (B) Fourth Carbon Black The fourth carbon black can be selected from the carbon blacks exemplified as the second carbon black, including preferred embodiments.

[0158] The DBP absorption amount, average particle size (average primary particle size), and ratio to the fourth rubber component of the fourth carbon black can be selected from the ranges described for the DBP absorption amount X2, average particle size, and ratio to the second rubber component of the second carbon black, including preferred ranges.

[0159] (C) Fourth filling system compounding agent The fourth crosslinked rubber composition may further contain a fourth filler compound. Examples of the fourth filler compound include a fourth filler.

[0160] Examples of the fourth filler include the fillers exemplified as the first filler. The fillers can be used alone or in combination of two or more. Among the fillers, silica is preferred as the fourth filler.

[0161] Silica includes dry silica, wet silica, and surface-treated silica. Furthermore, silica can be classified by manufacturing method into categories such as dry-processed white carbon, wet-processed white carbon, colloidal silica, and precipitated silica. These silicas can be used individually or in combination of two or more types. Among these silicas, silica with surface silanol groups (anhydrous silicic acid, hydrated silicic acid) is preferred, and hydrated silicic acid with a high number of surface silanol groups exhibits strong chemical bonding with rubber components.

[0162] The average particle diameter (average primary particle diameter) of silica is, for example, 1 to 500 nm, preferably 3 to 300 nm, more preferably 5 to 100 nm, and more preferably 10 to 50 nm.

[0163] Furthermore, the specific surface area for nitrogen adsorption of silica by the BET method is, for example, 50 to 400 m². 2 / g, preferably 100-300m 2 / g, more preferably 150-200m 2 It is / g.

[0164] The proportion of the fourth filling compound is, for example, 5 to 100 parts by mass, preferably 10 to 80 parts by mass, more preferably 20 to 60 parts by mass, and more preferably 30 to 50 parts by mass, per 100 parts by mass of the fourth rubber component.

[0165] (D) Fourth crosslinking compound The fourth crosslinked rubber composition may further contain a fourth crosslinking compound. Examples of fourth crosslinking compounds include a fourth crosslinking agent (vulcanizing agent) for crosslinking the fourth rubber component, as well as a fourth cocrosslinking agent (crosslinking aid or vulcanization aid), a fourth crosslinking accelerator (vulcanization accelerator), and a fourth crosslinking retarder (vulcanization retarder). Of these, the fourth crosslinking compound preferably contains at least a fourth crosslinking agent and a fourth cocrosslinking agent, and a combination of a fourth crosslinking agent and a fourth cocrosslinking agent is particularly preferred.

[0166] The fourth crosslinking agent can be selected from the crosslinking agents exemplified as the first crosslinking agent, including preferred embodiments.

[0167] The proportion of the fourth crosslinking agent is, for example, 1 to 20 parts by mass, preferably 2 to 10 parts by mass, and more preferably 3 to 5 parts by mass, per 100 parts by mass of the fourth rubber component.

[0168] The proportion of organic peroxide is, for example, 0.5 to 10 parts by mass, preferably 0.7 to 5 parts by mass, more preferably 0.8 to 4 parts by mass, and more preferably 1 to 3 parts by mass, per 100 parts by mass of the fourth rubber component.

[0169] The proportion of the metal oxide is, for example, 0.1 to 30 parts by mass, preferably 0.2 to 20 parts by mass, more preferably 0.3 to 10 parts by mass, more preferably 0.5 to 5 parts by mass, and most preferably 1 to 3 parts by mass, per 100 parts by mass of the first rubber component.

[0170] The fourth cocrosslinking agent can be selected from the cocrosslinking agents exemplified as the first cocrosslinking agent, including preferred embodiments.

[0171] The proportion of the fourth co-crosslinking agent (crosslinking aid) can be selected from a range of approximately 0.2 to 40 parts by mass per 100 parts by mass of the fourth rubber component, based on solid content, for example, 0.3 to 10 parts by mass, preferably 0.5 to 8 parts by mass, more preferably 0.7 to 5 parts by mass, and more preferably 1 to 3 parts by mass.

[0172] The proportion of the fourth crosslinking compound is, in terms of solid content, for example, 1 to 30 parts by mass, preferably 1.5 to 20 parts by mass, more preferably 2 to 10 parts by mass, and more preferably 3 to 8 parts by mass, per 100 parts by mass of the fourth rubber component.

[0173] (E) 4 Other combination agents The fourth crosslinked rubber composition may further contain conventional additives used in rubber compositions for toothed belts. These conventional additives can be selected from those exemplified as the first other compounding agents, including preferred embodiments.

[0174] In particular, the proportion of the processing agent or processing aid is, for example, 0.1 to 5 parts by mass, preferably 0.3 to 3 parts by mass, and more preferably 0.5 to 1.5 parts by mass, per 100 parts by mass of the fourth rubber component.

[0175] The proportion of the anti-aging agent is, for example, 0.1 to 10 parts by mass, preferably 0.5 to 5 parts by mass, and more preferably 1 to 3 parts by mass, per 100 parts by mass of the fourth rubber component.

[0176] The proportion of the plasticizer is, for example, 1 to 50 parts by mass, preferably 2 to 30 parts by mass, more preferably 3 to 20 parts by mass, and more preferably 5 to 15 parts by mass, per 100 parts by mass of the fourth rubber component. The plasticizer may be an ether ester-based plasticizer.

[0177] The total proportion of the fourth other compounding agent is, for example, 0.1 to 50 parts by mass, preferably 1 to 30 parts by mass, more preferably 5 to 25 parts by mass, and more preferably 10 to 20 parts by mass, per 100 parts by mass of the fourth rubber component.

[0178] The average thickness of the back rubber layer is, for example, 0.3 to 3 mm, preferably 0.5 to 2 mm. The average thickness of the back portion (average thickness of the back portion at the tooth root) is, for example, 1 to 5 mm, preferably 1.5 to 4 mm.

[0179] [Heart wire] On the back of the belt, a core wire extending along the belt circumferential direction is embedded on the inner circumference side of the back rubber layer. This core wire acts as a tensile body, improving the running stability and strength of the toothed belt. Furthermore, on the back, the core wire, which is usually a twisted cord extending along the belt circumferential direction, is embedded at predetermined intervals in the belt width direction. Multiple core wires parallel to the longitudinal direction may be arranged, but from the viewpoint of productivity, they are usually embedded in a spiral shape. When arranged in a spiral shape, the angle of the core wire with respect to the longitudinal direction of the belt may be, for example, 5° or less, and from the viewpoint of belt running performance, it is preferable that it is as close to 0° as possible.

[0180] More specifically, the core wires may be embedded at predetermined intervals (or pitches) (or at equal intervals) from one end to the other in the belt width direction on the back, as shown in Figure 1. The spacing (spinning pitch), which is the distance between the centers of adjacent core wires, should be greater than the core wire diameter, and depending on the core wire diameter, it may be, for example, 0.5 to 3.5 mm, preferably 0.8 to 3 mm, and more preferably 1 to 2.8 mm.

[0181] The core wire may be formed from a twisted cord made by twisting together multiple strands or multifilament threads. Of these, a twisted cord of strands is preferred, and one strand may be formed by bundling filaments (long fibers). There are no particular limitations on the thickness of the filaments forming the twisted cord, the number of filaments converged, the number of strands, and the twist configuration.

[0182] The twisted cord forming the core wire may be a single-strand, double-strand, or Lang-strand cord. By using a Lang-strand core wire, where the twist direction of the lower twist and the twist direction of the upper twist are the same, the bending stiffness is lower compared to double-strand or single-strand cords, resulting in excellent bending fatigue resistance.

[0183] The fibers forming the core are not particularly limited, and examples include synthetic fibers such as polyester fibers (polyalkylelelate fibers, poly(p-phenylene naphthalate) fibers), polybenzoxazole fibers, acrylic fibers, and polyamide fibers (aliphatic polyamide fibers, aramid fibers, etc.), as well as inorganic fibers such as glass fibers, carbon fibers, and metal fibers (steel fibers). These fibers can be used individually or in combination of two or more types. From the viewpoint of low elongation and high strength, synthetic fibers such as polyester fibers and polyamide fibers, and inorganic fibers such as glass fibers and carbon fibers are commonly used as fibers forming the core.

[0184] In applications involving particularly high loads, multifilament carbon fiber yarns are preferably used. Examples of carbon fibers used include those manufactured by Toray Industries, Inc., under the trade name "Torayca".

[0185] Carbon fiber multifilament yarns can be selected from multifilament yarns with different filament counts, such as 6K and 12K. 6K refers to a multifilament yarn with 6,000 filaments, and 12K refers to a multifilament yarn with 12,000 filaments. The fineness of 6K multifilament yarn is approximately 400 tex, and the fineness of 12K multifilament yarn is approximately 800 tex.

[0186] If the fineness of carbon fiber multifilament yarn is greater than 1000 tex, there is a risk that its flexural fatigue resistance will decrease. Conversely, if the fineness of carbon fiber multifilament yarn is less than 300 tex, the material cost will increase, and the number of under-twisted yarns required to produce a core wire with sufficient tensile strength will increase, leading to an increase in labor costs.

[0187] In one embodiment of the toothed belt of the present invention, the core wire is a carbon fiber cord (12K-1 / 0) made by single-twisting one 12K multifilament yarn (fineness approximately 800 tex). Alternatively, the core wire may be a Lang-twisted carbon fiber cord (12K-1 / 4) made by first twisting one 12K multifilament yarn (fineness approximately 800 tex) to create a pre-twisted yarn, and then combining four of these pre-twisted yarns and twisting them together. Note that "12K-1 / 0" indicates a twisted cord made by single-twisting one 12K multifilament yarn, and "12K-1 / 4" indicates a twisted cord made by first twisting one 12K multifilament yarn to create a pre-twisted yarn, and then combining four of these pre-twisted yarns and twisting them together. Similarly, for example, "12K-1 / 3" indicates a twisted cord made by first twisting one 12K multifilament yarn to create a base twist, then combining three of these base twists and twisting them together. "12K-4 / 0" indicates a twisted cord made by combining four 12K multifilament yarns and twisting them together in a single-ply manner.

[0188] The core wire may be subjected to an adhesive treatment to enhance its adhesion to the fourth crosslinked rubber composition. For example, the adhesive treatment may involve immersing the stranded cord in a resorcinol-formaldehyde-latex treatment solution (RFL treatment solution), followed by heating and drying to form a uniform adhesive layer on the surface of the stranded cord. The RFL treatment solution is a mixture of latex and an initial condensate of resorcinol and formalin. The latex may be, for example, chloroprene rubber, styrene-butadiene-vinylpyridine terpolymer (VP latex), nitrile rubber, or hydrogenated nitrile rubber. Furthermore, the adhesive treatment may involve pre-treating with an epoxy compound or isocyanate compound before treatment with the RFL treatment solution.

[0189] The average diameter (average wire diameter) of the stranded cord (or core wire) is, for example, 0.2 to 2.5 mm, preferably 0.5 to 2.3 mm, more preferably 0.7 to 2.2 mm, and 0.8 to 2.1 mm is preferred for applications where particularly high loads are applied. If the core wire diameter is too thin, the elongation of the core wire will increase, which may cause tooth breakage (loss of teeth). If the core wire diameter is too thick, the fatigue resistance of the core wire will decrease, which may cause core wire breakage. In one embodiment of the present invention, the core wire diameter is adjusted to 1.1 mm.

[0190] [Characteristics of toothed belts] The toothed belt of the present invention has high conductivity, for example, an electrical resistance value R of 6 × 10 5 It is preferable that the electrical resistance is less than or equal to ×L / W(Ω) [where L is the distance between electrodes (mm) and W is the width of the electrodes (mm) (however, if the width of the belt is smaller than the width of the electrodes, then the width of the belt)]. The specific electrical resistance value can be selected according to the type of toothed belt, but for example it is 2.88 MΩ or less (particularly 1.5 MΩ or less), for example 0.001 to 2.88 MΩ, preferably 0.01 to 2.5 MΩ, more preferably 0.05 to 2 MΩ, more preferably 0.05 to 1 MΩ, and most preferably 0.07 to 0.5 MΩ. These electrical resistance values ​​may also be the electrical resistance values ​​of the belt after use.

[0191] In this application, the electrical resistance of the toothed belt can be measured by the method described in the examples below.

[0192] <Method for manufacturing toothed belts> The toothed belt of the present invention may be manufactured, for example, by the following method (pre-forming method).

[0193] [Preparation process for the first rubber layer precursor] If the tooth portion includes a tooth cloth, first, a tooth cloth precursor is prepared to form the tooth cloth, and uncrosslinked rubber sheets are prepared to form multiple rubber layers, such as a first rubber layer precursor which is an uncrosslinked rubber sheet that forms the first rubber layer (surface rubber layer), a second rubber layer precursor which is an uncrosslinked rubber sheet that forms the second rubber layer (internal rubber layer), and a back rubber layer precursor which is an unvulcanized rubber sheet that forms the back rubber layer.

[0194] In particular, if the first rubber layer precursor contains first short fibers, it is preferable to subject it to the first rubber layer precursor preparation process shown below in order to orient the first short fibers in a predetermined direction.

[0195] In the first rubber layer precursor preparation step, the first short fibers can be oriented (arranged) in a predetermined direction during the process of preparing an uncrosslinked rubber sheet by rolling the rubber composition, which has been kneaded in a Banbury mixer or the like, using rolls or a calender. Specifically, a conventional method for oriented the first short fibers in a predetermined direction (one direction on the sheet surface) is to pass the rubber between a pair of calender rolls with a predetermined gap between them and roll it into a sheet, thereby obtaining a rolled sheet in which the first short fibers are oriented in the rolling direction.

[0196] The same method can be used to orient the short fibers when the second rubber layer and the back rubber layer contain short fibers (especially when the second rubber layer contains second short fibers).

[0197] [Pre-molding process] Next, a tooth cloth precursor is wound around the outer surface of a cylindrical mold having multiple grooves (recesses) corresponding to the teeth of a toothed belt. Subsequently, if the first rubber layer precursor contains first short fibers, a first rubber precursor, which is an uncrosslinked rubber sheet for forming the first rubber layer (surface rubber layer), and a second rubber layer precursor, which is an uncrosslinked rubber sheet for forming the second rubber layer (internal rubber layer), are wound around its outer surface in sequence, with the orientation direction of the first short fibers of the first rubber precursor oriented in the direction of the belt's longitudinal direction, to form a laminate. The laminate is then heated in a predetermined apparatus to a temperature (for example, about 70-90°C) at which the rubber composition softens, and pressure is applied to the laminate from the outer surface to press the rubber composition of the uncrosslinked rubber sheet and the tooth cloth precursor into the grooves (recesses) of the cylindrical mold, thereby forming teeth and obtaining a semi-crosslinked pre-molded body. In this press-fitting process to form the teeth, the tooth cloth stretches to conform to the contour of the teeth and is positioned on the outermost surface. Inside it, the first rubber layer is positioned along the contour of the teeth, and the first short fibers are also arranged in the direction of the contour of the teeth while remaining aligned in the longitudinal direction of the belt. Furthermore, a second rubber layer is positioned inside, forming a layered structure. If the teeth do not contain tooth cloth, the first rubber precursor is wrapped around the outer surface of the cylindrical mold instead of the tooth cloth precursor.

[0198] Alternatively, instead of using a cylindrical mold, a flat press mold (flat mold) having multiple grooves (recesses) corresponding to the teeth may be used to form the teeth by press-fitting the rubber composition of the uncrosslinked rubber sheet and the tooth fabric precursor into the grooves (recesses) of the flat mold using the above procedure. In this method, after demolding the preform from the flat mold, the preform is wrapped around and attached to a cylindrical mold having multiple grooves (recesses) corresponding to the teeth (fitting the teeth and grooves), and the process moves to the next step.

[0199] [Crosslinking molding process] The twisted cord constituting the core wire is wound spirally around the outer surface of the obtained pre-molded body at a predetermined pitch (so that the pitch is predetermined in the axial direction of the cylindrical mold). Furthermore, a back rubber layer precursor, which is an uncrosslinked rubber sheet that forms the back rubber layer, is wound around the outer surface to form an uncrosslinked belt molded body (uncrosslinked laminate).

[0200] Next, with the uncrosslinked belt molded body positioned on the outer circumference of the cylindrical mold, a rubber jacket, which acts as a vapor barrier, is placed over it. Subsequently, the jacketed belt molded body and the cylindrical mold are housed inside a crosslinking molding device such as a vulcanizing can. When the belt molded body is heated and pressurized inside the crosslinking molding device, the desired shape is formed, and the crosslinking reaction of the uncrosslinked and semi-crosslinked rubber components contained in the belt molded body causes each component to join together and harden integrally, forming a sleeve-shaped crosslinked molded body (crosslinked belt sleeve).

[0201] [Cutting process] Finally, multiple toothed belts are obtained by cutting the bridging belt sleeve, which has been demolded from the cylindrical mold, to a predetermined width. [Examples]

[0202] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples. The raw materials used, preparation methods, evaluation methods, etc., are shown below.

[0203] [Rubber composition]

[0204] [Table 1]

[0205] [Table 2]

[0206] [Table 3]

[0207] [Table 4]

[0208] [Table 5]

[0209] [Materials for rubber compositions] HNBR: Zetpol 2010, manufactured by Nippon Zeon Co., Ltd., iodine value 11 mg / 100 mg HNBR containing unsaturated metal carboxylate: Zeon Corporation's "Zeoforte ZSC2295CX," base HNBR:unsaturated metal carboxylate (mass ratio) = 100:110, iodine value of base HNBR 28 mg / 100 mg Aramid short fibers: "Conex" manufactured by Teijin Limited, average fiber length 3 mm, average fiber diameter 14 μm Nylon staple fibers: "Leona" manufactured by Asahi Kasei Corporation, polyamide 66, average fiber length 3 mm, average fiber diameter 27 μm Stearic acid: "Stearic acid Tsubaki" manufactured by NOF Corporation. Carbon Black A: "Seas S" manufactured by Tokai Carbon Co., Ltd., average particle size 66nm, DBP absorption 68mL / 100g Carbon Black B: Mitsubishi Chemical Corporation's "Mitsubishi Carbon #3230B," average particle size 23nm, DBP absorption 140mL / 100g Carbon Black C: "Seas 3" manufactured by Tokai Carbon Co., Ltd., average particle size 28nm, DBP absorption 101mL / 100g Carbon Black D: Asahi Carbon Co., Ltd. "Asahi #65", average particle size 44nm, DBP absorption 120mL / 100g Carbon Black E: Denka Co., Ltd. "Denka Black (granular)", average particle size 35 nm, DBP absorption 160 mL / 100 g Carbon Black F: Asahi Carbon Co., Ltd. "Asahi F-200GS", average particle size 38nm, DBP absorption 180mL / 100g Carbon Black G: Ketjenblack EC300J, manufactured by Lion Specialty Chemicals Co., Ltd., average particle size 40nm, DBP absorption 365mL / 100g Silica: "UltraSil VN-3" manufactured by Evonik Degussa Japan Co., Ltd., specific surface area 155 - 195 m 2 / g Calcium carbonate: "Super #1500" manufactured by Maruo Calcium Co., Ltd., average particle diameter 1.5 μm Zinc oxide: "Zinc Oxide Type 2" manufactured by Sakai Chemical Industry Co., Ltd., average particle diameter 0.55 μm Antioxidant: p,p'-dioctyldiphenylamine, "Nonflex OD3" manufactured by Seiko Chemical Co., Ltd. Organic peroxide: 1,3-bis(t-butylperoxyisopropyl)benzene, theoretical active oxygen content 9.45% Cocrosslinking agent: N,N'-m-phenylenedimaleimide, "Barnock PM" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Plasticizer: "Adekasizer RS700" manufactured by ADEKA Corporation

[0210] [Core wire] A carbon fiber cord (12K-1 / 0, tensile modulus of elasticity 230 GPa) was produced by single-twisting one 12K multifilament yarn ["Torayca T700SC-12000" manufactured by Toray Industries, Inc., single fiber fineness 0.67 dtex, total fineness 800 tex], and an adhesion treatment was performed with an HNBR-based overcoat treatment agent to obtain a core wire with a core wire diameter of 1.1 mm.

[0211] [Tooth cloth and treatment of tooth cloth] (Examples 1 - 28 and Comparative Examples 1 - 5 and 8 - 18) The woven fabrics shown in Table 6 were subjected to dipping treatment using an RFL treatment liquid and a rubber paste to produce tooth cloth precursors. Specifically, for the RFL treatment, two types of RFL treatment liquids (RFL1, RFL2) shown in Table 7 were used, and dipping treatments were performed in the order of RFL1 and RFL2. Thereafter, for the rubber paste treatment as well, two types of rubber pastes (rubber paste 1, rubber paste 2) shown in Table 8 were used, and dipping treatments were performed in the order of rubber paste 1 and rubber paste 2.

[0212]

Table 6

[0213]

Table 7

[0214] [Table 8]

[0215] (Comparative Example 6) The tooth fabrics were prepared in the same manner as in Examples 1-28 and Comparative Examples 1-5 and 8-18, except that the polyester yarn used for the weft of the tooth fabric was changed to a conductive yarn containing a conductive filler (conductive polyester fiber, "U300HXBE 31T5" manufactured by Teijin Frontier Co., Ltd.).

[0216] (Comparative Example 7) The tooth cloths were prepared in the same manner as in Examples 1-28 and Comparative Examples 1-5 and 8-18, except that the RFL treatment solutions (RFL1 and RFL2) used for the tooth cloths in Examples 1-28 and Comparative Examples 1-5 and 8-18 were each prepared by adding 3 parts by mass of carbon black B, which has a relatively high DBP absorption capacity, to 100 parts by mass of the original RFL treatment solution.

[0217] [Preparation of uncrosslinked rubber sheets] For forming the teeth and back (back rubber layer), each rubber composition shown in Tables 1 to 5 was kneaded using a Banbury mixer, and the resulting kneaded rubber was rolled to a predetermined thickness using a calender roll to produce an uncrosslinked rubber sheet. The short fibers contained in the uncrosslinked rubber sheet were oriented in the rolling direction. In this application, each rubber composition is denoted by R1 to R38.

[0218] [Manufacturing of toothed belts] In the examples and comparative examples, toothed belts with a total thickness of 9.8 mm, tooth profile G14M, tooth height (including tooth cloth) of 6.1 mm, tooth pitch of 14 mm, number of teeth of 100, circumference of 1400 mm, and width of 20 mm were manufactured using a pre-forming method as shown below.

[0219] Tables 10 to 17 show the tooth structure (layer structure) and the rubber composition used in each rubber layer of the toothed belts produced in each example and comparative example.

[0220] (Comparative Example 1) A press mold (flat type) having multiple grooves (recesses) corresponding to the teeth of a toothed belt was used to laminate a tooth fabric precursor for forming the tooth fabric, an uncrosslinked rubber sheet (R2, sheet thickness 1.40 mm) for forming the first rubber layer, and an uncrosslinked rubber sheet (R10, sheet thickness 2.10 mm) for forming the second rubber layer in that order. The laminate was then pressed for 240 seconds at a temperature of 90°C and a press pressure (surface pressure) of 20.2 MPa to produce a semi-crosslinked pre-molded body.

[0221] Next, a pre-molded body was wrapped around a cylindrical mold and attached (fitting the teeth with the grooves of the cylindrical mold), and the stranded cord constituting the core wire was spun spirally around the outer surface of the pre-molded body (tension: 300-900 N / strand, spinning pitch: 2.35 mm, spinning speed: 1.5 m / s). Furthermore, an uncrosslinked rubber sheet (R11, sheet thickness 1.50 mm) that forms the back rubber layer was wrapped around the outer surface to form an uncrosslinked belt molded body (uncrosslinked laminate). The uncrosslinked rubber sheet was wrapped so that the orientation direction of the nylon short fibers contained in the sheet was in the longitudinal direction (circumferential direction) of the belt.

[0222] Next, using a vulcanizing vessel, cross-linking molding was performed for 40 minutes under conditions of a heating temperature of 179°C and a vapor pressure of 0.83 MPa to produce a cross-linked molded body (cross-linked belt sleeve).

[0223] Finally, a toothed belt was obtained by cutting the bridging belt sleeve, which was demolded from the cylindrical mold, to a width of 20 mm.

[0224] (Comparative Examples 2-4 and Examples 1-4) Except for the use of R3 in Comparative Example 2, R4 in Comparative Example 3, R9 in Comparative Example 4, R5 in Example 1, R6 in Example 2, R7 in Example 3, and R8 in Example 4 as the uncrosslinked rubber sheet forming the first rubber layer, toothed belts were manufactured in the same manner as in Comparative Example 1.

[0225] (Example 5) A toothed belt was manufactured in the same manner as in Example 3, except that R1 was used as the uncrosslinked rubber sheet forming the second rubber layer.

[0226] (Comparative Example 5) A toothed belt was manufactured in the same manner as in Comparative Example 1, except that only one type of uncrosslinked rubber sheet, R7 (sheet thickness 3.50 mm), was used to form the teeth.

[0227] (Comparative Example 6) A toothed belt was manufactured in the same manner as in Comparative Example 1, except that only one type of uncrosslinked rubber sheet (R10, sheet thickness 3.50 mm) was used to form the teeth, and the polyester fibers used in the weft of the tooth fabric were changed to conductive threads containing conductive fillers, as described above.

[0228] (Comparative Example 7) A toothed belt was manufactured in the same manner as in Comparative Example 1, except that only one type of uncrosslinked rubber sheet (R10, sheet thickness 3.50 mm) was used to form the teeth, and as mentioned above, an RFL treatment solution was used in which carbon black B, which has a relatively high DBP absorption rate, was added in an amount of 3 parts by mass per 100 parts by mass of the original RFL treatment solution for the RFL treatment of the tooth cloth.

[0229] (Comparative Example 8 and Examples 6-9) Except for using R12 in Comparative Example 8, R13 in Example 6, R14 in Example 7, R15 in Example 8, and R16 in Example 9 as the uncrosslinked rubber sheet forming the first rubber layer, toothed belts were manufactured in the same manner as in Example 5.

[0230] (Comparative Examples 9-12) Except for using R17 in Comparative Example 9, R18 in Comparative Example 10, R19 in Comparative Example 11, and R20 in Comparative Example 12 as the uncrosslinked rubber sheet forming the first rubber layer, toothed belts were manufactured in the same manner as in Example 5.

[0231] (Comparative Examples 13-14 and Examples 10-12) Except for using R21 in Example 10, R22 in Comparative Example 13, R23 in Comparative Example 14, R24 in Example 11, and R25 in Example 12 as the uncrosslinked rubber sheet forming the first rubber layer, toothed belts were manufactured in the same manner as in Example 5.

[0232] (Comparative Examples 15-18 and Examples 13-16) Except for using R26 in Comparative Example 15, R27 in Comparative Example 16, R28 in Comparative Example 17, R33 in Comparative Example 18, R29 in Example 13, R30 in Example 14, R31 in Example 15, and R32 in Example 16 as the uncrosslinked rubber sheet forming the first rubber layer, toothed belts were manufactured in the same manner as in Example 5.

[0233] (Examples 17-21) Except for using R34 in Example 17, R35 in Example 18, R36 in Example 19, R37 in Example 20, and R38 in Example 21 as the uncrosslinked rubber sheet forming the second rubber layer, toothed belts were manufactured in the same manner as in Example 5.

[0234] (Example 22) A toothed belt was manufactured in the same manner as in Example 5, except that the thickness of the uncrosslinked rubber sheet forming the first rubber layer was 0.35 mm and the thickness of the uncrosslinked rubber sheet forming the second rubber layer was 3.15 mm.

[0235] (Example 23) A toothed belt was manufactured in the same manner as in Example 5, except that the thickness of the uncrosslinked rubber sheet forming the first rubber layer was 0.70 mm and the thickness of the uncrosslinked rubber sheet forming the second rubber layer was 2.80 mm.

[0236] (Example 24) A toothed belt was manufactured in the same manner as in Example 5, except that the thickness of the uncrosslinked rubber sheet forming the first rubber layer was 2.10 mm and the thickness of the uncrosslinked rubber sheet forming the second rubber layer was 1.40 mm.

[0237] (Example 25) A toothed belt was manufactured in the same manner as in Example 5, except that the thickness of the uncrosslinked rubber sheet forming the first rubber layer was 2.80 mm and the thickness of the uncrosslinked rubber sheet forming the second rubber layer was 0.70 mm.

[0238] (Example 26) A toothed belt was manufactured in the same manner as in Example 6, except that the thickness of the uncrosslinked rubber sheet forming the first rubber layer was 0.35 mm and the thickness of the uncrosslinked rubber sheet forming the second rubber layer was 3.15 mm.

[0239] (Example 27) A toothed belt was manufactured in the same manner as in Example 13, except that the thickness of the uncrosslinked rubber sheet forming the first rubber layer was 0.35 mm and the thickness of the uncrosslinked rubber sheet forming the second rubber layer was 3.15 mm.

[0240] (Example 28) A toothed belt was manufactured in the same manner as in Example 16, except that the thickness of the uncrosslinked rubber sheet forming the first rubber layer was 2.80 mm and the thickness of the uncrosslinked rubber sheet forming the second rubber layer was 0.70 mm.

[0241] [Evaluation and Judgment] For each test specimen (Examples 1-28 and Comparative Examples 1-18), a comparative verification was performed on machinability, durability, jumping torque, electrical conductivity (whether the electrical resistance of the belt tooth surface was sufficiently low), and manufacturing cost to determine whether a toothed belt capable of solving the problem of the present invention had been obtained.

[0242] [Workability] (Test method) The tooth shape of the toothed belt in the test specimen was visually observed to confirm whether the specified tooth shape was formed (presence or absence of tooth shape defects), and judged according to the following criteria. In other words, if the specified tooth shape was not formed (defective shape), it was determined that the toothed belt could not be manufactured and it was rejected.

[0243] (Judgment Criteria) a Judgment: The specified tooth shape is formed (no shape defect). d Judgment: The specified tooth shape is not formed (there is a shape defect).

[0244] [Durability Running Performance (Durability Running Test)] (Test Method) As shown in Figure 3, a toothed belt was mounted on a two - axis running test machine equipped with a driving pulley (Dr.) with 28 teeth and a driven pulley (Dn.) with 28 teeth, and the running time until a failure (tooth loss in the tooth part) occurred in the toothed belt was measured as the running life. The rotational speed of the driving pulley was 1800 rpm, the axial load of the driven pulley at the time of mounting the toothed belt was 1930 N, the load torque was 224.7 N·m, and the ambient temperature was 25°C (room temperature).

[0245] In this test, if no failure occurred in the toothed belt even when the running time reached 200 hours, it was judged that the durability performance was sufficient, and the test was terminated when the 200 - hour mark was reached. On the other hand, if a failure occurred before reaching 200 hours, the test was terminated at the time when the failure occurred, and the running time until then was taken as the durability life. Regarding the running time, the running time of Comparative Example 1 (200 hours) was set as 1.00, and the running times of each Example and Comparative Example were converted into relative values and shown. If this value is less than 1.00, it indicates that the durability performance is insufficient compared to the toothed belt of Comparative Example 1, and if it is 1.00, it can be said that it has sufficient durability performance equal to or better than that of Comparative Example 1.

[0246] (Judgment Criteria) a Judgment: When the running time is 1.00 c Judgment: When the running time is 0.90 or more and less than 1.00 d Judgment: When the running time is less than 0.90

[0247] From the perspective of durability running performance, toothed belts with a c - judgment or higher were considered qualified.

[0248] [Jumping Torque (Jumping Test)] (Test Method) Using a two-axis running test machine (torque measurement test machine) with the layout shown in Figure 3, a toothed belt was wrapped between a drive pulley (number of teeth: 28) and a driven pulley (number of teeth: 28), and the distance between the pulleys was adjusted so that the axial load on the driven pulley was 1930N. Then, the drive pulley was rotated at 1800 rpm, and the load on the driven pulley was continuously increased while the belt was running. The load torque applied to the drive pulley when jumping (tooth skipping) occurred was measured as the jumping torque. The jumping torque value was used as an indicator of jumping performance, and a higher jumping torque value indicates a superior toothed belt that is less prone to tooth skipping.

[0249] The jumping torque values ​​are shown relative to the values ​​of the examples and comparative examples, with the jumping torque value of Comparative Example 1 set to 1.00. A value of 1.00 or less indicates that no reinforcing effect is observed on the toothed belt of Comparative Example 1, while a value exceeding 1.00 indicates that the rigidity (deformation resistance) of the teeth is improved by the reinforcing effect. The higher this value, the more advanced the reinforcing effect.

[0250] (Judgment criteria) A judgment: If the jumping torque was 1.08 or higher. B rating: If the jumping torque is 1.00 or greater and less than 1.08. d judgment: If the jumping torque is less than 1.00

[0251] From the perspective of tooth rigidity (deformation resistance), toothed belts with a rating of B or higher were deemed acceptable.

[0252] [Electrical resistance value (conductivity test)] The electrical resistance of the belt tooth surface was measured in accordance with the laboratory method specified in ISO 9563 (2015). As shown in Figure 4, a toothed belt 11 with a width of 20 mm was set on an insulating resin plate 12 with the tooth surface facing upward, and a pair of brass electrodes 13 with a width (W) of 20 mm were fitted onto the tooth surface with a distance (L) of 96 mm between the electrodes. A weight 15 was placed on both electrodes 13 via a weight stand 14, applying a total load of 1.5 kgf. After attaching the terminals of an insulation resistance meter to the electrodes 13, a voltage of 500 V was applied, and the electrical resistance was measured 5 seconds after the voltage was applied. The measurement was performed at a room temperature of 23°C and a relative humidity of 50%. Before fitting the electrodes 13 to the toothed belt 11, conductive paint (Polycalm PTP-G1501, manufactured by Pluscoat Co., Ltd.) was applied between the toothed belt 11 and the electrodes 13. Electrical resistance was measured at five points, dividing the belt length into approximately five equal parts, and the average value was used. A smaller electrical resistance value indicates a better effect in preventing static electricity buildup on the belt, and the electrical resistance value R of the belt tooth surface was determined to be R = 6 × 10⁻⁶. 5 A test is considered successful if the electrical resistance value (conductivity) does not exceed ×L / W(Ω) [where L is the distance between electrodes (mm) as shown in Figure 4, and W is the width of the electrodes (mm) (however, if the width of the belt is smaller than the width of the electrodes, the width of the belt is used)]. In other words, under the above measurement conditions, the pass / fail of the electrical resistance value (conductivity) is determined by the upper limit of the electrical resistance value R being R = 6 × 10 5 ×96 / 20 = 2.88 × 10 6 Since (Ω) = 2.88 (MΩ), an electrical resistance value of 2.88 MΩ or less was considered acceptable.

[0253] The electrical resistance values ​​were measured before and after running the belt for 200 hours, under the same conditions as the endurance driving test. If the belt failed before reaching 200 hours, the electrical resistance value measured at that time was used as the electrical resistance value after running.

[0254] (Judgment criteria) Judgment was made according to the criteria shown in Table 9, and from the perspective of electrical conductivity, a toothed belt with a b judgment or above was considered qualified. That is, an a judgment means that it is less than 0.50 MΩ both before and after the endurance running test; a b judgment means that it does not exceed 1.50 MΩ and either before or after the endurance running test is 0.50 MΩ or more and less than 1.50 MΩ; a c judgment means that it does not exceed 2.88 MΩ and either before or after the endurance running test is 1.50 MΩ or more and 2.88 MΩ or less; a d judgment means that either before or after the endurance running test exceeds 2.88 MΩ.

[0255]

Table 9

[0256] From the perspective of electrical conductivity, a toothed belt with a c judgment or above was considered qualified.

[0257] [Manufacturing cost] (Test method) The costs (amounts) of manufacturing the toothed belts were quantified and compared. The manufacturing cost (amount) of Comparative Example 1 was set as 1.00, and the manufacturing costs of each Example and Comparative Example are shown in relative values.

[0258] (Judgment criteria) a judgment: When the manufacturing cost of the toothed belt is 0.98 or less c judgment: When the manufacturing cost of the toothed belt is greater than 0.98 but 1.00 or less d judgment: When the manufacturing cost of the toothed belt is greater than 1.00

[0259] From the perspective of manufacturing cost, a toothed belt with a c judgment or above was considered qualified.

[0260] [Overall judgment] Based on the judgments of each evaluation item, an overall evaluation was made according to the following judgment criteria.

[0261] Rank A: When all evaluation items are a judgments (qualified) Rank B: No C rating in any evaluation category, but at least one B rating (Pass) Rank C: No 'd' ratings in any evaluation category, but at least one 'c' rating is given (Pass). Rank D: If at least one evaluation item receives a 'd' rating (fail).

[0262] [Verification Results and Discussion] Tables 10-17 show the verification results of the toothed belts obtained in the examples and comparative examples.

[0263] [Table 10]

[0264] [Table 11]

[0265] [Table 12]

[0266] [Table 13]

[0267] [Table 14]

[0268] [Table 15]

[0269] [Table 16]

[0270] [Table 17]

[0271] (Comparative Examples 6-7) Comparative Examples 6 and 7 are examples of toothed belts in which the rubber layer forming the teeth is made of a single layer of rubber composition R10, and the tooth cloth, which is the outer surface that comes into contact with the pulley, is made conductive (antistatic).

[0272] Comparative Example 6 showed improved conductivity of the tooth surface by using conductive thread in the tooth fabric of the rubber layer forming the teeth, resulting in a low electrical resistance value before the endurance run. In the endurance run test, the toothed belt ran for 200 hours (relative value 1.00) without failure, but the electrical resistance value after the endurance run increased, possibly due to partial loss of conductive thread as the tooth fabric wore down during the run, resulting in a d rating (failure) in the conductivity test evaluation. The jumping test also received a d rating (failure). Furthermore, the use of expensive conductive thread due to the complex processing affected the manufacturing cost of the toothed belt, resulting in a d rating in the manufacturing cost evaluation item as well, thus resulting in an overall rank of D.

[0273] In Comparative Example 7, carbon black B, which has a relatively high DBP absorption rate, was added to the RFL treatment solution of the tooth cloth forming the rubber layer of the teeth, and the tooth cloth was immersed in this solution. As a result, carbon black B was impregnated into the tooth cloth, improving the conductivity of the tooth surface, and the electrical resistance value before the endurance run was low. However, perhaps because the addition of carbon black B to the RFL treatment solution relatively decreased the RFL solid content concentration and reduced adhesion, the belt failed (poor adhesion) before reaching 200 hours (relative value 0.80) in the endurance run test, resulting in a d rating (failure) in the endurance run test. However, the electrical resistance value remained low after the endurance run, and the conductivity test evaluation was a rarity 'a'. The jumping test also received a d rating (failure). Furthermore, the method of adding carbon black B to the RFL treatment solution used in Comparative Example 7 is also expensive to manufacture, so Comparative Example 7 also received a d rating (failure) in the manufacturing cost evaluation, resulting in an overall rank of D.

[0274] (Comparative Examples 1-3, Examples 1-3) Comparative Examples 1-3 and Examples 1-3 are examples of toothed belts in which the second rubber layer, positioned inside the teeth, is formed from the same rubber composition R10 as in Comparative Examples 6-7, and it was verified whether conductivity (antistatic properties) could be imparted to the first rubber layer, which is positioned on the surface side along the contour of the teeth.

[0275] These examples show toothed belts in which carbon black B (DBP absorption amount X1 = 140 mL / 100 g) was used as the primary carbon black, and the first rubber layer was formed using rubber compositions R2 to R7, in which the mass ratio Y1 of carbon black B to 100 parts by mass of the primary rubber component was varied. In all examples, the toothed belts ran for 200 hours (relative value 1.00) without failure during the durability running test. Furthermore, since the manufacturing cost was also low, the manufacturing cost evaluation was rated as "a" except for Comparative Example 1.

[0276] In the conductivity test, the following trends were observed. In Comparative Example 1, where the mass ratio Y1 of carbon black B to 100 parts by mass of rubber component in the first rubber layer was small (Y1=2, X1×Y1=280), the electrical resistance values ​​before and after the endurance run exceeded 2,000 MΩ, which was excessive, and conductivity could not be obtained (d rating). When the mass ratio Y1 of carbon black B was increased compared to Comparative Example 1, the electrical resistance values ​​before and after the endurance run decreased (conductivity improved), with Comparative Example 2 (Y1=50, X1×Y1=7,000) at 23.5 MΩ and Comparative Example 3 (Y1=60, X1×Y1=8,400) at 3.17 MΩ, but it did not reach the level required to pass ISO9563(2015) (2.88 MΩ or less) (d rating). Furthermore, increasing the mass ratio Y1 of carbon black B resulted in lower electrical resistance values ​​(improved conductivity) in Example 1 (Y1=65, X1×Y1=9,100), Example 2 (Y1=70, X1×Y1=9,800), and Example 3 (Y1=75, X1×Y1=10,500), achieving high conductivity (low electrical resistance) that meets the ISO9563(2015) standard (2.88MΩ or less). In addition, the electrical resistance values ​​after the endurance run were 0.16MΩ in Example 1, 0.09MΩ in Example 2, and 0.06MΩ in Example 3, maintaining high conductivity (low electrical resistance) and meeting the ISO9563(2015) standard (2.88MΩ or less).

[0277] Furthermore, in all three examples (1-3), the improvement in conductivity after driving compared to before driving was also an unexpected result.

[0278] (Example 4 and Comparative Example 4) Examples 4 and Comparative Example 4 are based on Example 3, in which the rubber composition forming the first rubber layer is changed from R7 to R8 and R9, respectively, and the mass ratio Y1 of carbon black B to 100 parts by mass of the first rubber component is increased.

[0279] In Example 4 (X1 × Y1 = 11,200) where Y1 = 80, similar to Example 3, the electrical resistance value before endurance running was 0.13 MΩ, achieving high conductivity (low electrical resistance value) that meets the ISO9563 (2015) standard (2.88 MΩ or less). Furthermore, the electrical resistance value after endurance running was 0.03 MΩ, maintaining high conductivity (low electrical resistance value) that also meets the ISO9563 (2015) standard (2.88 MΩ or less) (rating a).

[0280] However, in Comparative Example 4, where Y1=90, the excessive carbon black resulted in poor fluidity of the rubber composition (uncrosslinked rubber sheet), making it difficult to form the teeth. As a result, the predetermined tooth shape could not be formed, leading to a manufacturing failure (d rating) in terms of processability, and an overall rank of D. Therefore, from the viewpoint of processability, it was confirmed that the upper limit of Y1 should be less than 90.

[0281] (Example 5) This is an example of a toothed belt in which the rubber composition forming the second rubber layer is changed to R1 compared to Example 3. There are no major differences from Example 3 except that the second rubber layer is a rubber layer with a lower modulus of elasticity. Therefore, the same effect as Example 3 was confirmed in each test.

[0282] (Comparative Example 5) In this toothed belt, the entire tooth rubber layer is a conductive layer (antistatic layer) rather than being divided into two layers. In contrast to Example 3, the first and second rubber layers are formed with the same rubber composition R7 (Y1=75, X1×Y1=10,500), resulting in an example where the tooth rubber layer is formed as a single layer (conductive layer).

[0283] In the conductivity test, similar to Example 3, the electrical resistance value before endurance driving was 0.10 MΩ, achieving high conductivity (low electrical resistance value) that meets the ISO9563 (2015) standard (2.88 MΩ or less). However, because the tooth rubber layer near the core wire also contains a large amount of carbon black, a decrease in adhesion between the core wire and the tooth rubber layer, and a decrease in belt flexibility may have affected the endurance driving test. As a result, the belt failed before reaching 200 hours (relative value 0.70), and the endurance driving test was judged as d (failure). However, the electrical resistance value remained low after endurance driving, and the conductivity test evaluation was rated as a.

[0284] (Effects obtained) From the results of Examples 1 to 5, it can be said that high conductivity (low electrical resistance) is obtained when the amount of carbon black B (X1=140) added (mass ratio Y1 to 100 parts by mass of rubber component) is 65 parts by mass or more, and the product of the amount of DBP absorbed by carbon black X1 and the amount of carbon black added Y1 (X1 × Y1) is 9000 or more.

[0285] These results show that even toothed belts with a conductive layer (antistatic layer) on the tooth rubber layer that is not located on the outer surface, when the teeth include tooth fabric, can achieve a high level of conductivity (low electrical resistance) that meets the ISO 9563 (2015) standard. Furthermore, it was found that high conductivity (low electrical resistance) can be maintained even after endurance driving.

[0286] In particular, the toothed belts in Examples 3-5, which received an A rank in the overall evaluation, can be said to be good toothed belts that strike a good balance between running life and economy (manufacturing cost) and conductivity (antistatic properties).

[0287] Furthermore, the fact that conductivity improved after driving compared to before driving in all of Examples 1 to 5 was also an unexpected result.

[0288] (Comparative Example 8, Examples 6-9) Based on Example 5, these examples involve changing the rubber composition forming the first rubber layer from R7 to R12-16, and using carbon blacks with different DBP absorption amounts for the first carbon black. In other words, these examples compare the results by setting Y1=75, similar to Example 5, and varying X1 and X1×Y1.

[0289] In these examples, as the DBP absorption amount X1 of the primary carbon black increased, there was a tendency for the electrical resistance value to decrease (improved conductivity) before and after endurance driving. In detail, in Comparative Example 8, where X1 was less than 120, the electrical resistance value before endurance testing did not meet the ISO9563(2015) standard (2.88 MΩ or less) in terms of conductivity. On the other hand, in Examples 6 (X1=120, X1×Y1=9,000), 5 (X1=140, X1×Y1=10,500), 7 (X1=160, X1×Y1=12,000), 8 (X1=180, X1×Y1=13,500), and 9 (X1=365, X1×Y1=27,375), where X1 was 120 or more, high conductivity (low electrical resistance value) meeting the ISO9563(2015) standard (2.88 MΩ or less) was achieved. Furthermore, the electrical resistance values ​​after endurance testing also maintained high conductivity (low electrical resistance) at a level that meets ISO9563(2015) standards (2.88 MΩ or less) in Examples 6-9 (a or b rating). Therefore, the lower limit of X1 for obtaining a toothed belt capable of achieving conductivity at a level that meets ISO9563(2015) standards (2.88 MΩ or less) is 120, and it was confirmed that when X1 is 120 or higher, conductivity at a level that meets ISO9563(2015) standards (2.88 MΩ or less) can be maintained over a long period of time.

[0290] However, since carbon black G with an excessively large DBP absorption amount X1 is relatively expensive, Example 9 was ranked slightly lower (Rank C) in terms of manufacturing cost (economic efficiency).

[0291] (Comparative Examples 9-12, Comparative Example 8) Comparative Examples 9 to 12 are examples of toothed belts in which the first rubber layer is formed using rubber compositions R17 to R20, which are based on Comparative Example 8 (X1=101, Y1=75, X1×Y1=7,575) in which carbon black C with X1 less than 120 (DBP absorption amount X1=101 mL / 100 g) was used as the first carbon black, and in which the mass ratio Y1 of carbon black C to 100 parts by mass of the first rubber component was varied.

[0292] In Comparative Examples 9-11, the electrical resistance values ​​before endurance testing were excessively high: 2,000 MΩ in Comparative Example 9 (Y1=50), 1,203 MΩ in Comparative Example 10 (Y1=60), and 3.50 MΩ in Comparative Example 11 (Y1=80). These values ​​did not meet the ISO 9563 (2015) standard (2.88 MΩ or less) (d rating). Furthermore, in Comparative Example 12, where the amount of carbon black C was increased to Y1=90, the predetermined tooth shape could not be formed, similar to Comparative Example 4, resulting in a manufacturing impossibility issue (d rating) due to processability. Therefore, it was confirmed that when carbon black C (DBP absorption amount X1=101 mL / 100 g) is used as the first carbon black, it is impossible to achieve the ISO 9563 (2015) standard (2.88 MΩ or less) within the range of processability.

[0293] (Comparative Examples 13-14, Examples 11-12, 7) Comparative Examples 13-14 and Examples 11-12 are examples of toothed belts in which the first rubber layer was formed using rubber compositions R22-R25, which are based on Example 7 (X1=160, Y1=75, X1×Y1=12,000) in which carbon black E (DBP absorption amount X1=160mL / 100g) with X1 of 120 or more was used as the first carbon black, and in which the mass ratio Y1 of carbon black E to 100 parts by mass of the first rubber component was varied.

[0294] In these examples, similar to Comparative Examples 1-3 and Examples 1-4, which used carbon black B as the primary carbon black, a tendency was observed for the electrical resistance value to decrease (improved conductivity) before and after endurance testing as the mass ratio Y1 of carbon black E increased. Specifically, in Comparative Examples 13-14, where X1×Y1 was less than 9,000, the conductivity before endurance testing did not meet the ISO9563(2015) standard (2.88 MΩ or less), while in Examples 11-12, where X1×Y1 was 9,000 or more, high conductivity (low electrical resistance value) meeting the ISO9563(2015) standard (2.88 MΩ or less) was achieved. Furthermore, regarding the electrical resistance value after endurance testing, Examples 11-12 maintained high conductivity (low electrical resistance value) at the ISO9563(2015) standard (2.88 MΩ or less) (a or b rating).

[0295] (Examples 10, 6) Example 10 is an example of a toothed belt in which the first rubber layer is formed using a rubber composition R21, which is based on Example 6 (X1=120, Y1=75, X1×Y1=9,000) using carbon black D (DBP absorption amount X1=120 mL / 100 g) as the first carbon black, with a mass ratio Y1 of carbon black E to 100 parts by mass of the first rubber component set to 80.

[0296] In Example 10 (X1 × Y1 = 9,600), similar to Example 6, the electrical resistance value before endurance running was 0.62 MΩ, achieving high conductivity (low electrical resistance value) that meets the ISO9563 (2015) standard (2.88 MΩ or less). Furthermore, the electrical resistance value after endurance running was 0.13 MΩ, maintaining high conductivity (low electrical resistance value) that also meets the ISO9563 (2015) standard (2.88 MΩ or less) (rating b).

[0297] Based on the above results, it can be said that a toothed belt capable of achieving a conductivity level (2.88 MΩ or less) that meets ISO 9563 (2015) standards within the range of feasible processing can be obtained when X1 is 120 or greater and X1 × Y1 is 9,000 or greater.

[0298] (Examples 13-16, 9, Comparative Examples 15-18) Examples 13-16 and Comparative Examples 15-18 are examples of toothed belts in which the first rubber layer was formed using rubber compositions R26-R33, which are based on Example 9 (X1=365, Y1=75, X1×Y1=27,375) in which carbon black G with the maximum level X1 (DBP absorption amount X1=365mL / 100g) was used as the first carbon black, and in which the mass ratio Y1 of carbon black G to 100 parts by mass of the first rubber component was varied.

[0299] In these examples, as with Comparative Examples 1-3 and Examples 1-4, which used carbon black B as the primary carbon black, a tendency was observed for the electrical resistance value to decrease (improved conductivity) before and after endurance testing as the mass ratio Y1 of carbon black G increased. In Comparative Examples 15-17, where X1×Y1 was less than 9,000, the electrical resistance value before endurance testing was at a level that passed ISO9563(2015) (2.88 MΩ or less). While the desired result was not obtained, in Examples 13 (Y1=25, X1×Y1=9,125), 14 (Y1=30, X1×Y1=10,950), 15 (Y1=60, X1×Y1=21,900), and 16 (Y1=90, X1×Y1=29,200), where X1×Y1 was 9,000 or more, high conductivity (low electrical resistance) meeting the ISO9563(2015) standard (2.88 MΩ or less) was achieved. Furthermore, the electrical resistance values ​​after endurance testing also maintained high conductivity (low electrical resistance) at the ISO9563(2015) standard (2.88 MΩ or less) in Examples 13-16 (a or b rating). On the other hand, in Comparative Example 18, where the amount of carbon black G was further increased to Y1=90, the predetermined tooth shape could not be formed, similar to Comparative Example 4, and the product was deemed unmanufacturable (d rating) due to its machinability. Therefore, it was confirmed that the lower limit of Y1 for obtaining a toothed belt capable of achieving conductivity of 2.88 MΩ or less, which meets the ISO 9563 (2015) standard, is approximately 25, and the upper limit is approximately 80.

[0300] However, carbon black G, which has an excessively large DBP absorption X1, is relatively expensive, and the raw material costs were slightly increased. As a result, all of Examples 13-16 and 9 received a "c" rating in the manufacturing cost evaluation, and therefore received a low rank (rank C) in the overall evaluation.

[0301] (Examples 17-21, 5) Example 17 is an example of a toothed belt based on Example 5 (X1=140, Y1=75, X1×Y1=10,500), which received an overall A rating, but with the rubber composition forming the second rubber layer changed from R1 to R34. In other words, it is an example in which the DBP absorption amount X2 of the second carbon black was changed from 68 to 140. No difference was observed between Example 17 and Example 5 in each evaluation item.

[0302] Furthermore, based on Example 17, Examples 18 to 21 were examples of toothed belts in which the rubber composition forming the second rubber layer was changed from R34 to R35-R38 (changing the mass ratio Y2 of the second carbon black to 100 parts by mass of the second rubber component). In Examples 17 (Y2=2), 18 (Y2=10), and 19 (Y2=20), where Y2 was less than 25, no differences were observed in each evaluation item. On the other hand, when Y2 was 22 or higher, there was a tendency for the durability to decrease slightly as Y2 increased, and in Examples 20 (Y2=25) and 21 (Y2=30), the durability decreased slightly, resulting in a C rating, but it still met a practical passing standard.

[0303] Therefore, from the viewpoint of durable driving performance, it is preferable that the mass ratio Y2 of the second carbon black to 100 parts by mass of the second rubber component be less than 22.

[0304] (Examples 22-25, 5) Examples 22-25 are examples of toothed belts based on Example 5 (X1=140, Y1=75, X1×Y1=10,500), which received an overall rating of A, in which the ratio of the area occupied by the first rubber layer to the total area of ​​the rubber layers constituting the teeth (hereinafter referred to as the area ratio) was varied in a cross-sectional view of the teeth.

[0305] When the area ratio was varied from 10% (Example 22), 20% (Example 23), 40% (Example 5), 60% (Example 24), to 80% (Example 25), it was observed that as the area ratio increased, the electrical resistance decreased (conductivity improved), while the durability of the vehicle tended to decrease. Based on the balance between these two characteristics, Examples 23, 5, and 24, with area ratios of 20-60%, received an overall rating of A, while Example 22, with an area ratio of 10%, received a B, and Example 25, with an area ratio of 80%, received a C.

[0306] These results show that while there are differences in the balance between conductivity and durability depending on the area ratio, all examples met the passing standard (C rank or higher) in the overall assessment.

[0307] Therefore, it was confirmed that a toothed belt is provided that can solve the problem of the present invention and maintain conductivity (antistatic properties) during operation over a long period of time without reducing the belt's operating life or economic efficiency, as a practical level of conductivity and durable running performance can be achieved over a wide range of areas of the first rubber layer relative to the total rubber layer of the teeth. Furthermore, it was confirmed that a ratio of 20-60% of the area of ​​the first rubber layer relative to the total rubber layer of the teeth is preferable from the viewpoint of achieving the best balance (A rank) in each evaluation item, including conductivity and durable running performance.

[0308] (Examples 26-28) Examples 26-28 are examples that verify the relationship between area ratio and conductivity (X1, X1×Y1). Examples 26 and 27 are examples near the lower limit of the conductivity effect (when X1×Y1 is small and the area ratio is also small), with Example 26 having X1=120, X1×Y1=9,000 and an area ratio of 10%, and Example 27 having X1=365, X1×Y1=9,125 and an area ratio of 10%. Conversely, Example 28 is an example near the upper limit of the conductivity effect (when X1×Y1 is large and the area ratio is also large), with X1=365, X1×Y1=29,200 and an area ratio of 80%.

[0309] Example 26 is a toothed belt in which the area ratio was reduced to the minimum level compared to Example 6, which received an overall B rank. Although the conductivity (electrical resistance value) decreased to a C rank, each evaluation item was at a passing level (C rank or higher), and the overall rating was at a passing level (C rank). Similarly, Example 27 is a toothed belt in which the area ratio was reduced to the minimum level compared to Example 13, which received an overall B rank. Although the conductivity (electrical resistance value) decreased to a C rank, each evaluation item was at a passing level (C rank or higher), and the overall rating was at a passing level (C rank).

[0310] On the other hand, in Example 28, where the area ratio was increased to the maximum level compared to Example 16, where the conductivity was near the upper limit (X1 × Y1 = 29,200), sufficient conductivity was obtained, but there were concerns that the bending rigidity of the belt would increase, resulting in insufficient flexibility and reduced belt durability. As a result of the verification, although the durability running performance decreased to a C rating compared to Example 16, each evaluation item was at a passing level (C rating or higher), and the overall rating was at a passing level (C rank).

[0311] Therefore, in these Examples 26-28, the effects of the present invention were obtained, and it was confirmed that a toothed belt is provided that can maintain conductivity (antistatic properties) during operation for a long period of time without reducing the belt's running life and economic efficiency.

[0312] From the results of all the verifications above, it has been confirmed that by creating a toothed belt formed of a first rubber layer arranged on the surface side (inner surface side) of the teeth and a second rubber layer formed between the first rubber layer and the core wire, where X1 (mL / 100g) is the DBP absorption amount of the first carbon black relative to the rubber component of the first rubber layer, and Y1 is the mass ratio of the first carbon black to 100 parts by mass of the first rubber component, the problems of this invention can be solved, and a toothed belt can be obtained that does not increase manufacturing costs, does not reduce the belt's running life, and has a high level of conductivity (low electrical resistance value) while maintaining that conductivity over a long period of time even while running. [Industrial applicability]

[0313] The toothed belt (meshing transmission belt or toothed transmission belt) of the present invention can be used in combination with a toothed pulley in various fields where synchronization between input and output is required, such as power transmission mechanisms in vehicles such as automobiles and motorcycles, power transmission mechanisms such as motors and pumps in industrial machinery, machinery such as automatic doors and automated machines, office automation (OA) equipment components, coin handling equipment, photocopiers, and printers.

[0314] Furthermore, the toothed belt of the present invention can be used as a toothed belt for applications requiring antistatic properties, ranging from low loads to high loads (high horsepower), but it is particularly preferable to use it as a power transmission belt (timing belt or cogged belt) for industrial machinery and rear-wheel drive motorcycles in applications requiring high loads (high horsepower). [Explanation of Symbols]

[0315] 1…Toothed belt 1a...teeth part 1b...Root of the tooth 1c...back 2… Toothcloth 3…First rubber layer 4…Second rubber layer 5… Core wire 6... Back rubber layer

Claims

1. The back portion has a core wire embedded in it that extends along the circumference of the belt, The inner circumferential surface of the back portion is provided with a plurality of teeth formed at intervals in the circumferential direction of the belt, A toothed belt comprising a back rubber layer formed on the outer circumference side of the belt relative to the core wire, and a first rubber layer and a second rubber layer formed on the inner circumference side of the belt relative to the core wire, The back portion includes the back rubber layer, The tooth portion includes the first rubber layer and the second rubber layer interposed between the first rubber layer and the core wire. The first rubber layer is formed of a first crosslinked rubber composition comprising a first rubber component and a first carbon black, and The amount of DBP absorbed by the first carbon black is X １ (mL / 100g), Y is the mass ratio of parts by mass of the first carbon black to 100 parts by mass of the first rubber component. １ A toothed belt that satisfies all of the following requirements 1 to 3. Requirement 1: X １ ≥110 Requirement 2: 22 ≤ Y １ ≤88 Requirement 3: X １ ×Y １ ≥9000

2. The toothed belt according to claim 1, wherein the second rubber layer is formed of a second crosslinked rubber composition containing a second rubber component, and the proportion of second carbon black in the second crosslinked rubber composition is less than 22 parts by mass per 100 parts by mass of the second rubber component.

3. The second crosslinked rubber composition further contains a second carbon black, and the mass ratio, which is the number of parts by mass of the second carbon black with respect to 100 parts by mass of the second rubber component, is Y ２ When this is the case, the DBP absorption amount X of the second carbon black ２ and the mass ratio Y ２ The product (X ２ × Y ２ ) is less than 9000. The toothed belt according to claim 2

4. The toothed belt according to any one of claims 1 to 3, wherein the first rubber component comprises a first composite polymer comprising hydrogenated nitrile rubber and an unsaturated carboxylic acid metal salt, and the second rubber component comprises a second composite polymer comprising hydrogenated nitrile rubber and an unsaturated carboxylic acid metal salt.

5. The toothed belt according to any one of claims 1 to 3, wherein the first crosslinked rubber composition further comprises first short fibers.

6. The toothed belt according to any one of claims 1 to 3, wherein the modulus of elasticity of the first rubber layer is greater than the modulus of elasticity of the second rubber layer.

7. The toothed belt according to any one of claims 1 to 3, wherein the inner circumferential surface of the first rubber layer of the belt is made of toothed fabric.

8. The electrical resistance value R of the belt tooth surface, measured according to the method compliant with ISO 9563 (2015), is 6 × 10 ５ A toothed belt according to any one of claims 1 to 3, wherein the ratio × L / W (Ω) [where L is the distance between electrodes (mm) and W is the width of the electrodes (mm) (however, if the width of the belt is smaller than the width of the electrodes, the width of the belt)] is less than or equal to × L / W (Ω).

9. After 200 hours of operation under a load torque of 200-250 N·m, the electrical resistance value R of the belt tooth surface, measured according to the method compliant with ISO 9563 (2015), was 6 × 10⁻¹⁰. ５ A toothed belt according to claim 8, wherein the ratio ×L / W (Ω) [where L is the distance between electrodes (mm) and W is the width of the electrodes (mm) (however, if the width of the belt is smaller than the width of the electrodes, the width of the belt)] is less than or equal to ×L / W (Ω).

10. A method for manufacturing a toothed belt according to any one of claims 1 to 3, comprising a pre-molding step of producing a pre-molded body in which an uncrosslinked rubber sheet for forming a first rubber layer and an uncrosslinked rubber sheet for forming a second rubber layer are laminated.

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