Belt

Abstract

A belt 10 comprises: a base material layer 11; an inner layer 12 composed of an elastic material 115 and formed inside the base material layer 11; and an outer layer 13 composed of an elastic material 117 and formed outside the base material layer 11. The base material layer 11 includes: a first thread 111 extending in a width direction of the belt 10; a second thread 112 having a portion extending along the first thread 111 and a portion stretched between adjacent first threads 111; a knitting yarn 113 connecting the first thread 111 and the second thread 112; and a peripheral thread 114 being present on the outer layer 13 side. The belt 10 is excellent in dimensional stability and durability.

Description

belt

[0001] The present invention relates to belts used in papermaking processes.

[0002] The papermaking process includes multiple steps, such as a wire part where wet paper stock is placed on a wire and initially dewatered, a press part where the wet paper is further dewatered by pressing, a dryer part where the dewatered wet paper is dried, and a calender part where surface smoothness and gloss are imparted. Each of these parts uses an endless belt suited to its purpose, and the belt runs at high speed while continuously applying pressure to the surface. The press part, which is subjected to the most pressure and other loads in the manufacturing process, can be either a roll press or a shoe press, with the shoe press being the most commonly used. Even in the wire part, for example, a shoe press may be used, in which pressure is applied to a wet paper, wire, and belt interposed between a shoe and a roller. Also, in the calender part, for example, a shoe press may be used, in which pressure is applied to a paper and belt interposed between a shoe and a roller.

[0003] There are two types of shoe presses: open and closed. For example, in the closed shoe press method in the press part, wet paper, felt, and a belt are placed between the shoe and roller, and compressed air is introduced inside the belt, imitating the shape of the press roll by applying tension to the entire belt, and dewatering is performed under pressure from the inner shoe. The shoe press belt is always under pressure from the roll and is used in a sliding state with the shoe, so it must be sufficiently strong and durable.

[0004] Patent Documents 1 to 5 disclose shoe press belts having an inner layer that contacts the shoe, a base layer made of a woven fabric, and an outer layer that contacts the felt.

[0005] JP 11-247086 JP 11-256492 JP 2007-084961 JP 2005-307421 JP 05-179594

[0006] The belts described in Patent Documents 1 to 4 use a woven fabric as a base layer having an intersection where the weft and warp yarns are joined or connected at their intersections. When there is an intersection where the weft and warp yarns are entangled, fatigue occurs due to abrasion or compression, resulting in the problem of cracks occurring around the intersection. Patent Document 5 describes a base layer formed by spirally winding peripheral yarns (machine direction yarns) around a roll on which warp yarns (CD direction yarns) are stretched, and fixed with an elastomer cover material. In belts with such a base layer, the contact area where the peripheral yarns and warp yarns intersect and come into contact with each other can cause misalignment between the warp and peripheral yarns during use, resulting in dimensional instability. This problem occurs not only in shoe press belts in the press part, but also in belts used in other processes, such as calender belts in the calender part. Closed-type belts, in particular, have less freedom in belt running position than open-type belts, so belts used there require higher dimensional stability.

[0007] SUMMARY OF THE INVENTION It is an object of the present invention to provide a belt that has excellent dimensional stability and durability.

[0008] The present invention provides the following belt: A belt comprising a base layer, an inner layer made of an elastic material and formed inside the base layer, and an outer layer made of an elastic material and formed outside the base layer, wherein the base layer comprises: a first yarn extending in the width direction of the belt, a second yarn having a portion extending along the first yarn and a portion bridged between adjacent first yarns, a braiding yarn connecting the first yarn and the second yarn, and a peripheral yarn present between the base layer and the outer layer.

[0009] According to the present invention, a belt having excellent dimensional stability and durability can be provided.

[0010] Fig. 1 is a cross-sectional view showing an example of a belt. Fig. 2 is a diagram showing an example of a knitted fabric embedded in an elastic material of a base layer. Fig. 3 is a diagram showing an example of the arrangement of a second yarn relative to a first yarn. Fig. 4 is a diagram showing an example of a knitting yarn of a knitted fabric embedded in an elastic material of a base layer.

[0011] Belts according to embodiments will be described below with reference to the drawings. The present invention is not limited to the following embodiments, and modifications and improvements can be made to the following embodiments as appropriate based on the ordinary knowledge of those skilled in the art without departing from the spirit of the present invention. Dimensional relationships such as length, width, thickness, and width in the drawings have been changed as appropriate for clarity and simplification of the drawings, and do not represent actual dimensional relationships.

[0012] In each drawing, the Y direction is the length direction of the belt (the direction in which the belt travels), the X direction is the width direction of the belt, and the Z direction is the thickness direction of the belt.

[0013] 1, a belt 10 according to this embodiment includes a base layer 11, an inner layer 12 made of an elastic material 115 and formed inside the base layer 11, and an outer layer 13 made of an elastic material 117 and formed outside the base layer 11. In the case of a shoe press belt, the outer layer 13 may be provided with grooves 131 for dewatering a wet paper web, as shown in the figure.

[0014] The structure of the yarn embedded in the elastic material 116 of the base layer 11 will be specifically described below with reference to Figures 1 to 4. Figure 2 is a diagram showing an example of a knitted fabric embedded in the elastic material of the base layer. Figure 3 is a diagram showing an example of the arrangement of the second yarn relative to the first yarn. Figure 4 is a diagram showing an example of a knitted yarn of a knitted fabric embedded in the elastic material of the base layer.

[0015] (Base Material Layer 11) As shown in FIG. 1, the base material layer 11 includes a first yarn 111, a second yarn 112, a knitting yarn 113, and a peripheral yarn 114. More specifically, the base material layer 11 is configured by embedding a knitted fabric including the first yarn 111, the second yarn 112, and the knitting yarn 113, and the peripheral yarn 114 in an elastic material 116. The first yarn 111 is a yarn extending in the X direction (the width direction of the belt 10). As shown in FIG. 2, the first yarn 111 is configured by continuously arranging multiple first yarns 111a and 111b in a substantially parallel manner. The distance between the first yarns 111a and 111b is, for example, 2 to 4 mm. As shown in FIGS. 2 and 3, the second yarn 112 is a yarn having a portion 20 extending along the first yarn 111a or 111b and a portion 21 bridged between adjacent first yarns 111a and 111b. The knitting yarn 113 is a yarn that connects the first yarn 111 and the second yarn 112 at the portion 20 .

[0016] The distance between the portions 20 along the first yarn 111 where the second yarn 112 is connected by the braiding yarn 113 is, for example, 3 to 8 mm. The distance between the first yarns 111a and 111b and the distance between the portions 20 may be the same or different. These distances can be adjusted depending on the flexibility and durability required for the intended use of the belt. If the distance between the first yarns 111a and 111b is shorter than 2 mm, flexibility in the belt running direction may be reduced, so it is preferable to set the distance to 2 mm or more depending on the required flexibility. If the distance is longer than 4 mm, there is a risk of localized insufficient strength, making the belt unsuitable for papermaking belts. On the other hand, if the distance between the portions 20 is longer, the fiber density in the belt may decrease, making it more susceptible to cracking. Conversely, shortening the distance between the portions 20 increases durability.

[0017] The base material layer 11 has a structure in which the second yarns 112 are present only on one side of the first yarns 111 in the thickness direction of the base material layer 11, and the first yarns 111 and the second yarns 112 are not directly intertwined and connected, but are connected to each other by the knitting yarns 113. Therefore, when the belt runs under pressure, the portion where the first yarns 111 and the second yarns 112 overlap is easily bent, and stress is less likely to concentrate in that portion. Furthermore, this structure provides flexibility in the running direction of the belt.

[0018] 3, the second yarn 112 has, between two adjacent first yarns 111a, 111b, a portion 21 that is hung from one first yarn 111a to the other first yarn 111b, a portion 20 that extends along the other first yarn 111b, and a portion 21 that is hung from the other first yarn 111b to one first yarn 111a. The portion 21 is also a portion where a pair of second yarns 112 that are connected via a knitting yarn at a certain distance to a pair of upper and lower first yarns 111 (two adjacent first yarns 111a, 111b) intersect. At the intersecting portion 21, the portion where one second yarn 112a is hung and the portion where the other second yarn 112b is hung intersect with each other. A pair of second threads 112 are hung over a pair of first threads 111, and the intersecting portion 21 is hung from one first thread 111a to the other first thread 111b at an angle to the running direction of the belt, as shown in Figure 3.

[0019] With this structure, stress applied to the intersecting portion 21 is more easily dispersed in the inclined direction, further making it easier to avoid stress concentration. Also, even if a portion of the second yarn 112 is damaged as a result of strong tension being applied in the traveling direction during use of the belt 10, the impact can be contained at the portion 20 where the first yarn 111 and the second yarn 112 are connected by the knitting yarn 113. This limits the impact of the damage to only that portion of the second yarn 112, allowing the shape to be maintained and the impact of the damage to be reduced. As a result, it is easier to prevent misalignment and cracks between the warp and weft yarns during use of the belt.

[0020] Furthermore, the base material layer 11 has a surrounding yarn 114 between it and the outer layer 13 so as to cover the knitted fabric composed of the first yarn 111, the second yarn 112, and the knitting yarn 113, thereby increasing the durability against tension in the running direction of the belt when it is in use.

[0021] Therefore, the belt 10 according to this embodiment can suppress misalignment and cracks between the warp and weft yarns during use, and has excellent durability. Furthermore, by using plied yarns that are less likely to stretch as the peripheral yarns 114, durability against tension in the belt running direction during use can be further improved.

[0022] Next, details of each yarn used in the knitted fabric embedded in the elastic material 116 of the base layer 11 will be described. Strength is required in the width direction of the belt to maintain its shape, and flexibility is required in the running direction of the belt because bending loads are applied at the rotating parts of the rolls. Therefore, the first yarns 111 arranged in the width direction of the belt are yarns with a larger twist coefficient than the second yarns 112 in order to maintain their shape and strength. In particular, it is preferable that the first yarns 111 are thicker than the second yarns 112. The twist coefficient will be described later.

[0023] The first yarn 111 is preferably, for example, a plied yarn. A plied yarn can be obtained, for example, by twisting multiple raw yarns to make a lower yarn, and then twisting the resulting multiple lower yarns to make an upper yarn. It is particularly preferable to twist three or more lower yarns to make an upper yarn. The twist direction of the upper yarn may be the same as that of the lower yarn, but is preferably the opposite direction. For example, if the twist of the upper yarn is a Z twist, the twist of the lower yarn is an S twist.

[0024] The thickness of the raw yarn constituting the first yarn 111 is, for example, 1100 to 1670 dtex. For example, if two raw yarns each having a thickness of 1100 dtex are twisted together to make a lower yarn, and three of these lower yarns are twisted together to make an upper yarn, the thickness of the first yarn 111 will be 6600 dtex.

[0025] The twist coefficient of the first yarn 111 is, for example, 50 or more, more preferably 60 or more, and even more preferably 66 or more. This is to obtain sufficient durability. On the other hand, if the twist coefficient is too high, it becomes difficult to provide elasticity, so the upper limit of the twist coefficient is preferably 150, and more preferably 130. The twist coefficient of the lower yarn of the first yarn 111 is preferably in the range of 50 to 130, for example.

[0026] In this specification, a medium twist yarn is defined as a yarn having a twist factor of 66 to 130. Therefore, it is more preferable that the first yarn 111 is a plied yarn and a medium twist yarn.

[0027] The second yarn 112 is required to be flexible because it is subjected to a bending load, and is therefore preferably, for example, a single twist yarn. A single twist yarn is a yarn made by twisting a single raw yarn. The raw yarn thickness of the second yarn 112 is, for example, 1100 to 1670 dtex. The twist coefficient of the second yarn 112 is, for example, 70 or less. More preferably, it is 65 or less, and even more preferably, it is 60 or less. This is to obtain sufficient flexibility. The lower limit of the twist coefficient may be 0, but from the viewpoint of durability, the lower limit is preferably 10.

[0028] In this specification, a loosely twisted yarn is defined as a yarn having a twist factor of 10 to 65. Therefore, it is more preferable that the second yarn 112 is a single twisted yarn and a loosely twisted yarn.

[0029] The knitting yarn 113 is a yarn used to connect the first yarn 111 and the second yarn 112 at the portion 20, and it is sufficient if it has a strength sufficient to maintain the connection state between the first yarn 111 and the second yarn 112. For this reason, the knitting yarn 113 may be a yarn that is sufficiently thin compared to the first yarn 111 and the second yarn 112. For example, the knitting yarn 113 may be a yarn having a thickness of 84 dtex and 36 filaments.

[0030] The peripheral yarns 114 need to be strong enough to withstand the tension generated by the compressed air inside the belt 10. Therefore, the thickness of the raw yarns constituting the peripheral yarns 114 is, for example, 1100 to 1670 dtex, and the twist coefficient is, for example, in the range of 50 to 130.

[0031] 4 illustrates an example of a connection between the first yarn 111 and the second yarn 112 by the knitting yarn 113. Symbols such as L1 indicate continuous portions of the knitting yarn 113, and are continuous in the order of L4'...L10', L1...L10, L1"...L4". Note that L10' and L10, L1 and L1" and the like are similarly continuous portions.

[0032] As shown in FIG. 4 , in the knitting yarn 113, L1 extends along the first yarn (not shown), is bent at the rear end of L1, and is connected to L2. L2 extends along the first yarn (not shown) in the opposite direction to L1, and is connected to L3. The junction of L1 and L2 is hooked to the junction of L7 and L8. The junction of L2 and L3 is hooked to the junction of L7' and L8'. L3 extends along the first yarn (not shown) in the same direction as L1, and is connected to L4. The junction of L3 and L4 is passed between L7 and L8. L4 extends along the first yarn (not shown) in the same direction as L1, and is connected to L5. L5 is passed under the first yarn (not shown) and is connected to L6.

[0033] L6 extends along the first thread (not shown) in the same direction as L1 and is connected to L7. The junction of L6 and L7 is hooked to the junction of L2" and L3". L7 extends along the first thread (not shown) in the opposite direction to L1 and is connected to L8. The junction of L7 and L8 is hooked between L1 and L2. L8 extends along the first thread (not shown) in the same direction as L1 and is connected to L9. The junction of L8 and L9 is passed between L2" and L3". L9 extends along the first thread (not shown) in the same direction as L1 and is connected to L10. L10 is passed under the first thread (not shown) in the opposite direction to L5 and is connected to L1".

[0034] 2, the second yarn 112 is inserted into the loop formed between L2 and L3 and the loop formed between L7 and L8, and is connected to the first yarn 111 by L5 and L10. The materials of the first yarn 111, the second yarn 112, and the knitting yarn 113 may all be the same or different. For example, polyester may be used for all of them.

[0035] (Inner layer 12) In the belt 10, the inner layer 12 is required to have appropriate flexibility because it is the part that comes into contact with the shoe when used in, for example, a shoe press belt. For this reason, the inner layer 12 is made of an elastic material 115. For example, a urethane resin is used. The urethane resin of the inner layer 12 preferably has a hardness of Shore A 90 to 97. The thickness of the inner layer 12 is, for example, 0.5 to 2 mm. This is to obtain sufficient flexibility and durability.

[0036] (Outer Layer 13) In the belt 10, the outer layer 13 is the part that comes into contact with the felt when used as a shoe press belt, and the part that comes into contact with the wire or paper stock when used as a belt for a wire part or a calender part. Therefore, like the inner layer 12, it is required to have a moderate degree of flexibility. For this reason, the outer layer 13 is also made of an elastic material 117. For example, a urethane resin is used. The material of the outer layer 13 may be the same as or different from that of the inner layer 12. It is preferable that the urethane resin of the outer layer 13 also has a hardness of 90 to 97 Shore A.

[0037] The surface shape of the outer layer 13 can be changed as appropriate depending on the intended use of the belt 10 in each part of the papermaking process. For example, the surface shape of the outer layer 13 may be flat, or may have grooves 131 as shown in FIG. 1. The grooves 131 are used to facilitate dewatering of wet paper when used as a shoe press belt in the press part, for example. The grooves 131 may be continuous or discontinuous. The thickness of the outer layer 13 is, for example, 0.5 to 3 mm. This is to obtain sufficient flexibility and durability.

[0038] The belt 10 can be used as a belt for each part of the papermaking process, such as a shoe press belt for the wire part, press part, or calender part. The belt 10 can be used particularly as a shoe press belt for the press part, which requires high strength, and can also be used as a closed-type shoe press belt, which requires high dimensional stability.

[0039] [Method for Manufacturing Belt] The belt can be manufactured, for example, by the following method.

[0040] The inner layer 12 is formed by casting an elastic material 115 onto the surface of a rotating roll in the axial direction of the roll. Casting may be performed once, but is preferably repeated multiple times.

[0041] A knitted fabric including at least a first yarn 111, a second yarn 112, and a knitting yarn 113 is fixed on the formed inner layer 12. Then, while the roll is rotating, an elastic material 116 is cast in the roll axial direction until the elastic material 116 covers the knitted fabric, sealing it. Casting may be repeated multiple times until the surface texture of the sealed fabric is achieved. Then, a peripheral yarn 114 is spirally wound around the knitted fabric at a predetermined pitch.

[0042] With the roll rotating, the elastic material 116 is cast in the roll axial direction until it covers the peripheral yarns 114, thereby sealing them. It is preferable to repeat the casting process multiple times until the surface properties of the sealed area are achieved. In this manner, the base material layer 11 is formed on the inner layer 12. Then, with the roll rotating, the elastic material 117 is cast in the roll axial direction to form the outer layer 13 on the base material layer 11 with the peripheral yarns 114 sealed. Then, while the roll is rotating, the elastic material 117 is heated with a far-infrared heater or the like to harden the elastic material 117. The elastic material 117 for the outer layer can be a different material from the elastic material 115 for the inner layer and / or the elastic material 116 for the base layer, depending on the application of the belt.

[0043] The cured product is removed from the roll, and the surface of the cured outer layer 13 is cut and polished, and grooves 131 are formed as needed, thereby producing the belt 10.

[0044] [Manufacturing Method of Example 1] An inner layer (thickness: approximately 1.0 mm) was formed by casting urethane resin onto the surface of a rotating roll. Next, a knitted fabric having the configuration shown in FIG. 2 was placed on the surface of the inner layer, and the urethane resin was cast on the knitted fabric until it covered the surface (thickness: approximately 1.25 mm). Next, peripheral yarns were spirally wound around the surface of the sealed knitted fabric (thread spacing: approximately 2.4 mm), and the urethane resin was cast on the peripheral yarn until it covered the surface of the peripheral yarn (thickness: approximately 1.25 mm). A base layer was formed by casting urethane resin from the surface of the inner layer until it covered the knitted fabric and the surfaces of the peripheral yarn (thickness of the base layer: approximately 2.5 mm). An outer layer (thickness: approximately 2.5 mm) was formed by casting urethane resin on the surface of the base layer. The total thickness of the belt, including the inner layer, base layer, and outer layer, was approximately 6.0 mm. The rolls were then heated with a far-infrared heater or the like while rotating, curing the elastic materials 115, 116, and 117. The cured product was removed from the roll, and the surface of the outer layer was cut and polished to produce a belt with a thickness of approximately 6.0 mm. This was designated Example 1. The knitted fabric was formed using the yarns shown in Table 1 and then subjected to RFL (resorcinol-formalin-latex) treatment. The yarns shown in Table 2 were used as the peripheral yarns.

[0045]

[0046]

[0047] [Manufacturing Method for Comparative Example 1] An inner layer (thickness: approximately 1.0 mm) was formed by casting urethane resin onto the surface of a rotating roll. Next, weft yarns (CD yarns) were set on the surface of the inner layer, and the urethane resin was cast on the surface of the weft yarns until they covered the surface of the weft yarns (thread spacing: approximately 3.0 mm). Next, warp yarns (MD yarns) were spirally wound around the surface of the blocked weft yarns (thread spacing: 2.4 mm). The urethane resin was cast on the surface of the blocked weft yarns until it covered the surrounding yarns to form a base layer (thickness: approximately 2.5 mm). The surface of the base layer was cast with urethane resin to form an outer layer (thickness: approximately 2.5 mm). Then, while rotating, the roll was heated with a far-infrared heater or the like to harden the elastic material. The hardened product was removed from the roll, and the surface of the outer layer was cut and polished to produce a belt with a thickness of approximately 6.0 mm. This was designated Comparative Example 1. The yarns shown in Table 2 were used for the weft and warp yarns.

[0048] [Manufacturing Method for Comparative Example 2] The multi-woven base fabric shown in Table 3 was set on a roller, impregnated with urethane resin to approximately 50% of the base fabric's thickness, and then coated with the same material to a thickness of 1.0 mm or more. After vulcanization, the fabric was cut and polished, and the fabric was turned over so that the coated side was on the inside. The entire surface of the fabric was coated while the impregnated side of the fabric was impregnated. After vulcanization, the fabric was cut and polished. In this way, a belt with a thickness of approximately 6.0 mm was manufactured. This was designated Comparative Example 2.

[0049]

[0050] From each of the completed belts, rectangular belt pieces measuring 150 mm x 20 mm were cut out so that the belt was longer in the width direction (CD direction), and various tests were carried out.

[0051] [Bending test] In the bending test, a De Mattia bending tester described in JIS K6260:2017 (Vulcanized rubber and thermoplastic rubber - Determination of flex crack resistance and flex crack growth resistance (De Mattia method)) was used. The above-mentioned belt piece was used as the test piece. The test piece was placed on the upper and lower grips of the De Mattia bending tester at a position where the distance between the upper grip, which is the fixed part, and the lower grip, which is the moving part, was the maximum, and a bending test was performed in which the test piece was bent toward the outer layer under conditions of a chuck distance of 81 mm and an amplitude of 42 mm, and the number of times until a crack occurred was investigated.

[0052] [Penetration Test] In the penetration test, a test piece was prepared by making a cut in the lateral direction (MD) of the above-mentioned belt piece at the center position in the longitudinal direction down to the surface of the base material layer. This test piece was subjected to a bending test under the same conditions as in the above-mentioned [Bending Test], and the number of times until penetration was investigated.

[0053] In the bending test, cracks occurred in Comparative Examples 1 and 2 after 3 million bending cycles or less, but no cracks occurred even after 5 million bending cycles in Example 1. In the penetration test, penetration occurred in Comparative Example 1 after 300,000 bending cycles or less, and in Comparative Example 2 after 700,000 bending cycles or less, but no penetration occurred in Example 1 even after 1.2 million bending cycles.

[0054] [Method for confirming the knitted structure of the base layer of the belt] The knitted structure used in the base layer 11 is embedded in the elastic material 116, so it is not easy to confirm it, but the thickness of the yarn, the number of twists, and the twisting method can be confirmed by the following method.

[0055] 1. Cut out a sample of 10 cm or more square from the portion of the belt excluding the ends. 2. Melt the elastic material to remove the base material layer and check the knitting form (the relative positions of the first yarn, second yarn, and knitting yarn, and the twist method). If the elastic material is a urethane resin, DMF (dimethylformamide) can be used. 3. Unravel the first yarn, second yarn, and knitting yarn of the removed base material layer and check the yarn thickness D (dtex: measure the weight and convert to the weight per 1000 m) and the number of twists, which are converted into the number of twists T per unit length (1 m). 4. Calculate the twist coefficient K from the yarn thickness D and the number of twists T per unit length (1 m) using the following formula. 5. Perform steps 1 to 4 above at three locations and calculate the average.

[0056] K = T × √(D / 10000) where the meaning of each symbol is as follows: K: twist coefficient T: number of twists (times / m) D: yarn thickness (dtex)

[0057] REFERENCE SIGNS LIST 10 Belt 11 Base material layer 12 Inner layer 13 Outer layer 111, 111a, 111b First yarn 112, 112a, 112b Second yarn 113 Knitting yarn 114 Surrounding yarn

Claims

1. A belt comprising: a base layer; an inner layer made of an elastic material and formed on the inside of the base layer; and an outer layer made of an elastic material and formed on the outside of the base layer, wherein the base layer comprises: a first yarn extending in the width direction of the belt; a second yarn having a portion extending along the first yarn and a portion bridged between adjacent first yarns; and a knitted fabric formed of knitting yarn connecting the first yarn and the second yarn; and a peripheral yarn between the knitted fabric and the outer layer.

2. The belt according to claim 1, wherein the second thread has, between two adjacent first threads, a portion extending along one of the first threads, a portion passing from the one first thread to the other first thread, a portion extending along the other first thread, and a portion passing from the other first thread to the one of the first threads.

3. The belt according to claim 1, wherein the second yarns are present only on one side of the first yarns in the thickness direction of the base material layer.

4. The belt of claim 1, wherein the first yarns are medium twist yarns and the second yarns are loose twist yarns.

5. The belt of claim 1, wherein the first yarns are ply yarns and the second yarns are single twist yarns.

6. The belt of claim 1, wherein the first threads are thicker than the second threads.

7. A belt according to claim 4 or 5, wherein the first yarn has a higher twist coefficient than the second yarn.

8. The belt according to claim 1, wherein the elastic material is a urethane resin.

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