Friction transmission belt and manufacturing method thereof

Abstract

To provide a friction transmission belt that includes a reinforcing fabric but demonstrates superior productivity and economic efficiency, while exhibiting enhanced resistance to wear, and a method for producing the same.SOLUTION: A friction transmission belt includes a friction transmission surface that is at least partly covered with a reinforcing fabric, which includes a rubber composition containing a rubber component and a fabric. In an uncrosslinked product of the rubber composition, the minimum Mooney scorch viscosity at 125°C is controlled to 21 or less, and the rubber hardness Hs of the crosslinked product is controlled to 55 or more. The rubber composition may include carbon black, a co-crosslinker, an adhesion promoter, a non-reinforcing filler, and a tackifier. Both sides of the reinforcing fabric may be frictionally treated with the rubber composition. The content of the rubber composition in the reinforcing fabric may be 30-50 mass%. The friction transmission belt may be a wrapped V-belt with the reinforcing fabric as the outer fabric.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a friction power transmission belt such as a wrapped V-belt whose friction power transmission surface is formed with a V-shape inclination, and a method for manufacturing the same. [Background technology]

[0002] Friction transmission belts such as V-belts, V-ribbed belts, and flat belts are widely known as power transmission belts. V-belts come in two types: raw-edge type (raw-edge V-belts), which have a rubber layer with an exposed friction transmission surface (V-shaped side), and wrapped type (wrapped V-belts), which have a friction transmission surface covered with an outer sheath (cover fabric). They are used differently depending on the application due to the difference in the surface properties of the friction transmission surface (friction coefficient between the rubber layer and the cover fabric).

[0003] Wrapped V-belts are widely used in general industrial machinery such as compressors, generators, and pumps, as well as agricultural machinery such as combines, rice transplanters, and harvesters. Wrapped V-belts have the advantage of allowing moderate slippage during operation, preventing excessive strain on the transmission mechanism, and producing little noise. One of the characteristics required of wrapped V-belts is abrasion resistance. Wear of the outer covering of a wrapped V-belt can cause a decrease in tension and excessive slippage, leading to reduced power transmission and heat generation. Therefore, there is a demand for improved abrasion resistance in the outer covering of wrapped V-belts.

[0004] In response to such demands, Japanese Utility Model Laid-Open Publication No. 62-81742 (Patent Document 1) discloses a power transmission V-belt having a cover cloth coated or impregnated with an elastomer material mixed with ceramic powder attached to the surface that comes into contact with the pulley. This document states that this configuration prevents wear on the cover cloth, and that the ceramic powder rubs against the rust on the pulley during use, removing the rust from the pulley.

[0005] Furthermore, Japanese Patent Laid-Open Publication No. 2017-137994 (Patent Document 2) discloses a friction transmission belt coated with a reinforcing fabric containing metal particles, a binder, and a fabric. This document states that the above-described configuration exhibits the effect of removing rust that has formed on the pulley and suppresses wear of the friction transmission belt during operation. It also states that crosslinked rubber is preferable as the binder because of its excellent adhesion to the belt body. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Utility Model Application Publication No. 62-81742 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-137994 Summary of the Invention [Problem to be solved by the invention]

[0007] Although the inventions disclosed in Patent Documents 1 and 2 are effective in improving the wear resistance of friction transmission belts to a certain extent, they require the incorporation of ceramic powder or high-hardness metal particles into the reinforcing fabric (or cover fabric), which increases costs and reduces economic viability. In addition, uncrosslinked rubber compositions containing ceramic powder or high-hardness metal particles tend to increase in viscosity, making it difficult to rub the composition into the fabric.

[0008] Therefore, an object of the present invention is to provide a friction transmission belt in which at least a portion of the friction transmission surface is covered with a reinforcing fabric, which has excellent productivity and economy and excellent wear resistance even though it has a reinforcing fabric, and to manufacture a friction transmission belt with excellent wear resistance at low cost while maintaining good frictional operation in the manufacturing process of the reinforcing fabric. [Means for solving the problem]

[0009] As a result of extensive research to achieve the above object, the present inventors have found that the productivity, economy, and wear resistance of a friction drive belt having a reinforcing fabric can be simultaneously improved by adjusting the Mooney scorch minimum viscosity at 125°C and the rubber hardness Hs of a rubber composition contained in a reinforcing fabric covering the friction drive surface of the friction drive belt, and have completed the present invention.

[0010] That is, the friction transmission belt according to aspect [1] of the present invention is A friction transmission belt in which at least a portion of a friction transmission surface is covered with a reinforcing fabric, The reinforcing fabric includes a rubber composition containing a rubber component and a fabric, The rubber composition has a Mooney scorch minimum viscosity at 125°C of 21 or less in an uncrosslinked state, and a rubber hardness Hs of 55 or more in a crosslinked state.

[0011] Aspect [2] of the present invention is an aspect of the aspect [1], wherein the rubber composition contains carbon black, and the proportion of the carbon black is 45 to 55 parts by mass per 100 parts by mass of the rubber component.

[0012] Aspect [3] of the present invention is an aspect of the aspect [1] or [2], wherein the rubber composition contains a co-crosslinking agent, and the proportion of the co-crosslinking agent is 0.5 to 2.5 parts by mass per 100 parts by mass of the rubber component.

[0013] Aspect [4] of the present invention is any one of aspects [1] to [3], wherein the rubber composition contains an adhesion improver, and the proportion of the adhesion improver is 0.5 to 4 parts by mass per 100 parts by mass of the rubber component.

[0014] Aspect [5] of the present invention is any one of aspects [1] to [4], wherein the rubber composition contains a non-reinforcing filler, and the proportion of the non-reinforcing filler is 10 to 45 parts by mass per 100 parts by mass of the rubber component.

[0015] Aspect [6] of the present invention is any of aspects [1] to [5], wherein the rubber composition contains a tackifier, and the proportion of the tackifier is 5 to 30 parts by mass per 100 parts by mass of the rubber component.

[0016] Aspect [7] of the present invention is any one of aspects [1] to [6], wherein both surfaces of the reinforcing fabric are friction-treated with the rubber composition.

[0017] An embodiment [8] of the present invention is any one of the embodiments [1] to [7], wherein the proportion of the rubber composition in the reinforcing fabric is 30 to 50 mass %.

[0018] Aspect [9] of the present invention is any one of the aspects [1] to [8] above, which is substantially free of metal particles.

[0019] Aspect

[10] of the present invention is any one of aspects [1] to [9] above, wherein the reinforcing fabric is a wrapped V-belt that forms an outer skin fabric.

[0020] The present invention also includes, as aspect

[11] , a method for producing a friction transmission belt according to any one of aspects [1] to

[10] , which includes a friction step of producing a reinforcing fabric precursor by friction-treating at least one surface of a fabric with a rubber composition containing an uncrosslinked rubber component. [Effects of the Invention]

[0021] In the present invention, the Mooney Scorch minimum viscosity at 125°C and the rubber hardness Hs of the rubber composition contained in the reinforcing fabric covering the frictional power transmission surface of the frictional power transmission belt are adjusted, so that a frictional power transmission belt having excellent productivity and economy as well as excellent wear resistance can be provided even though it has a reinforcing fabric. More specifically, in the manufacturing process of the reinforcing fabric, a frictional power transmission belt having excellent wear resistance can be manufactured inexpensively while maintaining good frictional operation. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a schematic, partially cut, perspective view of a wrapped V-belt. [Figure 2] FIG. 2 is a graph showing the behavior of Mooney viscosity to explain the method for measuring the Mooney scorch minimum viscosity (Vm) and scorch time. DETAILED DESCRIPTION OF THE INVENTION

[0023] The present invention will be described in detail below, with reference to the accompanying drawings as necessary.

[0024] The friction power transmission belt of the present invention is not particularly limited as long as at least a portion of the surface (friction power transmission surface) that comes into contact with a pulley is covered with a reinforcing fabric containing a specific rubber composition and fabric, and may be a V-belt, a V-ribbed belt, a flat belt, etc. The friction power transmission belt may also be a belt formed with a friction power transmission portion (ribs, etc.), such as a wrapped V-belt, which has recently become popular for use under harsh conditions where it is prone to thermal degradation.

[0025] As shown in FIG. 1, the wrapped V-belt 1 comprises an endless belt body formed of an outer circumferential tension rubber layer (or upper core rubber layer) 2, an inner circumferential compression rubber layer (or V-core rubber layer) 4, and a core 3 embedded between the tension rubber layer 2 and the compression rubber layer 4 along the belt longitudinal direction (circumferential direction, direction A in the figure). The belt body is also covered by an outer cover fabric 5 (woven, knitted, nonwoven, etc.) covering the entire circumferential length of the belt. In this example, the core 3 is a cord (twisted cord) arranged at a predetermined interval in the belt width direction (direction B in the figure) and is in contact with the tension rubber layer 2 and the compression rubber layer 4, being interposed between the two layers. The wrapped V-belt is not limited to this structure. For example, an adhesive rubber layer may be interposed between the compression rubber layer 4 and the tension rubber layer 2 to improve adhesion between the core 3 and the tension rubber layer 2 or the compression rubber layer 4. The core 3 may be embedded between the tension rubber layer 2 and the compression rubber layer 4, and may be embedded in the compression rubber layer 4, for example, or may be embedded in the compression rubber layer 4 while being in contact with the tension rubber layer 2. Furthermore, the core 3 may be embedded in the adhesive rubber layer, or may be embedded between the compression rubber layer 4 and the adhesive rubber layer, or between the adhesive rubber layer and the tension rubber layer 2.

[0026] 1 has an inverted trapezoidal (V-shaped) cross section, and outer cover fabric 5 on both sides of the V-shaped inclination forms a frictional power transmission surface that comes into contact with the inner wall of the V-groove of the pulley. Therefore, in the wrapped V-belt, the reinforcing fabric may be formed on at least a partial area of ​​the frictional power transmission surface (for example, the entire frictional power transmission surface), but from the standpoint of productivity, it is preferable that the entire outer cover fabric be formed of the reinforcing fabric.

[0027] The reinforcing fabric and belt body that make up the friction drive belt, as well as the manufacturing method for the friction drive belt, are described in detail below. Conventional pulleys can be used, and in the case of V-belts, pulleys with V-grooves that correspond to the V-shape of the friction drive surface of the belt can be used.

[0028] [Reinforcing fabric] In the friction power transmission belt of the present invention, the reinforcing fabric needs to cover at least a portion of the friction power transmission surface. This is the case for wrapped V-belts as described above, but other friction power transmission belts may also have a reinforcing fabric covering at least a portion of the friction power transmission surface as well as areas other than the friction power transmission surface. For example, in raw edge V-belts, V-ribbed belts, etc., the non-friction power transmission surface may be covered with a reinforcing fabric serving as a backing fabric (a backing fabric corresponding to a tension rubber layer). Of these, reinforcing fabrics that cover friction power transmission surfaces such as the upper or lower surface of a flat belt or the side surface of a wrapped V-belt are preferred, and reinforcing fabrics that serve as outer covering fabrics for wrapped V-belts (V-belts whose entire area, including the surfaces that do not contact the pulleys, is covered with a reinforcing fabric) are particularly preferred.

[0029] In the present invention, by covering at least a portion of the friction transmission surface with a reinforcing fabric, the wear resistance of the reinforcing fabric (and the friction transmission belt including the reinforcing fabric) can be improved without impairing the workability of the friction treatment for manufacturing the reinforcing fabric.

[0030] (Rubber composition) In the friction transmission belt of the present invention, the rubber composition contained in the reinforcing fabric (rubber composition for reinforcing fabric) is adjusted to a specific Mooney scorch minimum viscosity and rubber hardness Hs, thereby adjusting the viscosity of the rubber composition in the friction treatment to a specific range, and the hardness of the reinforcing fabric after crosslinking can also be adjusted to a range that satisfies the required wear resistance. Generally, to produce a crosslinked rubber composition with high hardness, the viscosity of the uncrosslinked rubber composition used as the raw material tends to be high, and there is a trade-off between the high hardness of the crosslinked rubber and the viscosity of the raw material. In contrast, in the present invention, the increase in the viscosity of the uncrosslinked rubber composition can be suppressed to a moderate range while the hardness of the crosslinked rubber composition can be increased, thereby achieving both workability in the friction treatment and wear resistance.

[0031] The Mooney scorch minimum viscosity (minimum Mooney viscosity Vm) of the rubber composition for reinforcing fabric (uncrosslinked rubber composition) measured at 125°C is 21 or less, for example, 10 to 21, preferably 15 to 20.8, more preferably 17 to 20.5, even more preferably 19 to 20.3, and most preferably 19.5 to 20. If Vm is too high, it becomes difficult to rub the rubber composition evenly into the fabric during friction, and problems such as fabric tearing are likely to occur. On the other hand, while it is difficult to strictly specify the lower limit of Vm, if Vm is too low, it may be difficult to adjust the amount of adhesion to the fabric. For example, if Vm is too low, sufficient shear force may not be obtained during friction, making it difficult to reduce the amount of adhesion, which may reduce economic efficiency.

[0032] The scorch time t5 (total time from the start of the test through Vm to when the temperature rises 5 points above Vm) of the rubber composition for reinforcing fabric (uncrosslinked rubber composition) is, for example, 18 to 60 minutes, preferably 20 to 40 minutes, even more preferably 25 to 39 minutes, even more preferably 30 to 38 minutes, and most preferably 35 to 38 minutes. If the scorch time t5 is too short, there is a risk that "burning" will occur, in which crosslinking unintentionally progresses during the rubber mixing or friction treatment. On the other hand, if the scorch time t5 is too long, it will take a long time to complete crosslinking, which may reduce the productivity of friction transmission belts.

[0033] In the present application, the Mooney scorch minimum viscosity Vm and the scorch time t5 can be measured in accordance with the Mooney scorch test of JIS K 6300-1 (2013), and in detail, can be measured by the method described in the examples below.

[0034] The rubber hardness Hs of the rubber composition for reinforcing fabric (crosslinked rubber composition) is 55 or more, for example, 55 to 90, preferably 56 to 80, further preferably 57 to 70, more preferably 58 to 65, and most preferably 59 to 60. If the rubber hardness Hs of the uncrosslinked rubber composition is too low, the abrasion resistance decreases. On the other hand, if the rubber hardness Hs is too high, it becomes necessary to increase the amount of filler, crosslinking agent, etc. to increase the hardness, which also tends to increase Vm, and this may reduce workability.

[0035] In this application, the rubber hardness Hs of the crosslinked rubber composition refers to the value Hs (Type A) measured using a Type A durometer in accordance with the spring type durometer hardness test specified in JIS K 6253 (2012) (Vulcanized rubber and thermoplastic rubber - Determination of hardness), and may be simply referred to as rubber hardness. In detail, it can be measured by the method described in the examples below.

[0036] (A) Rubber component The rubber component (A) contained in the rubber composition for reinforcing fabric can be appropriately selected depending on the type of friction transmission belt. Examples of the rubber component (A) include diene rubbers (natural rubber, isoprene rubber, butadiene rubber, chloroprene rubber, styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (nitrile rubber), hydrogenated nitrile rubber (including a mixed polymer of hydrogenated nitrile rubber and an unsaturated carboxylic acid metal salt), ethylene-α-olefin elastomer, chlorosulfonated polyethylene rubber, alkylated chlorosulfonated polyethylene rubber, epichlorohydrin rubber, acrylic rubber, silicone rubber, urethane rubber, and fluororubber. These components can be used alone or in combination.

[0037] Of these rubber components, diene rubbers (natural rubber, chloroprene rubber, hydrogenated nitrile rubber, etc.) and ethylene-α-olefin elastomers (ethylene-propylene copolymer (EPM), ethylene-propylene-diene terpolymer (EPDM), etc.) are preferred, and for wrapped V-belts, chloroprene rubber is particularly preferred because it is relatively inexpensive and has excellent abrasion resistance, heat resistance, and adhesion to fabrics.

[0038] The proportion of the rubber component (A) in the rubber composition for reinforcing fabric can be selected from a range of about 10 to 90 mass%, for example, 20 to 80 mass%, preferably 25 to 70 mass%, further preferably 30 to 60 mass%, more preferably 35 to 50 mass%, and most preferably 40 to 45 mass%. If the proportion of the rubber component (A) is too low, there is a risk of reduced adhesion, and conversely, if it is too high, there is a risk of reduced abrasion resistance.

[0039] (B) Carbon black The rubber composition for reinforcing fabric may contain carbon black (B) as a reinforcing filler to increase hardness. Conventional friction rubbers have low hardness and insufficient abrasion resistance, but in the present invention, by containing carbon black in a predetermined proportion, hardness can be improved without reducing workability.

[0040] The average particle size (average primary particle size) of the carbon black (B) is, for example, 5 to 200 nm, preferably 10 to 150 nm, further preferably 20 to 100 nm, even more preferably 30 to 80 nm, and most preferably 50 to 70 nm. If the average particle size of the carbon black is too small, workability may decrease, whereas if it is too large, abrasion resistance may decrease.

[0041] In the present application, the average particle size of carbon black (B) can be measured using, for example, a scanning electron microscope (SEM) or a transmission electron microscope (TEM), and the arithmetic average particle size can be calculated by image analysis for an appropriate number of samples (for example, 50 samples).

[0042] In order to improve workability, it is preferable that the carbon black (B) contains soft carbon with a relatively large particle size. Generally, carbon black can be classified into either soft carbon, which has a relatively large particle size, or hard carbon, which has a relatively small particle size. Carbon black is sometimes classified based on the average particle size (average primary particle size) in the raw material state, but in the present application, it is classified based on the primary particle size of the carbon black contained in the rubber composition (particularly in the crosslinked rubber composition). That is, in the present application, the primary particle size of each primary particle of the carbon black contained in the rubber composition is measured, and carbon black with a primary particle size of 40 to 300 nm is referred to as soft carbon, and carbon black with a primary particle size of 1 nm or more but less than 40 nm is referred to as hard carbon.

[0043] The average primary particle size of the soft carbon may be, for example, 42 to 100 nm, preferably 45 to 80 nm, more preferably 50 to 75 nm, and even more preferably 60 to 70 nm. On the other hand, the average primary particle size of the hard carbon may be, for example, 10 to 38 nm, preferably 15 to 35 nm, more preferably 20 to 33 nm, and even more preferably 25 to 30 nm. The ratio of the average primary particle size of the soft carbon to the average primary particle size of the hard carbon is 10 / 1 to 1.1 / 1, preferably 8 / 1 to 1.3 / 1, more preferably 5 / 1 to 1.5 / 1, more preferably 3 / 1 to 1.8 / 1, and most preferably 2.5 / 1 to 2 / 1.

[0044] The proportion of soft carbon (proportion of particle number) in the carbon black (B) may be 10% or more, preferably 50% or more, further preferably 65% ​​or more, and even more preferably 70 to 90%. If the proportion of soft carbon is too low, the viscosity may increase, which may result in a decrease in workability or processability.

[0045] In the carbon black (B), the ratio of the number of soft carbon particles to the number of hard carbon particles (soft carbon / hard carbon) can be selected from a range of about 100 / 0 to 10 / 90, and is preferably 95 / 5 to 50 / 50, more preferably 90 / 10 to 65 / 35, and even more preferably 85 / 15 to 75 / 25, in order to achieve both workability and abrasion resistance.

[0046] In the present application, the ratio of the number of soft carbon particles to the number of hard carbon particles can be calculated based on the primary particle diameter measured using a transmission electron microscope, and in detail, can be measured by the method described in the examples below.

[0047] The iodine adsorption capacity of the carbon black (B) is, for example, 5 to 200 g / kg, preferably 10 to 100 g / kg, further preferably 15 to 80 g / kg, even more preferably 20 to 50 g / kg, and most preferably 23 to 30 g / kg. If the iodine adsorption capacity is too small, there is a risk of a decrease in abrasion resistance, whereas if it is too large, there is a risk of a decrease in workability.

[0048] In the present application, the iodine adsorption amount of carbon black (B) can be measured in accordance with the standard test method of ASTM D1510-17.

[0049] The proportion of carbon black (B) may be 30 parts by mass or more (particularly 41 parts by mass or more) per 100 parts by mass of the rubber component (A), for example, 30 to 60 parts by mass (particularly 43 to 58 parts by mass), preferably 44 to 57 parts by mass, further preferably 45 to 55 parts by mass, even more preferably 46 to 54 parts by mass, and most preferably 48 to 52 parts by mass. If the proportion of carbon black (B) is too low, it may be impossible to increase hardness, resulting in a risk of reduced abrasion resistance. Conversely, if it is too high, Vm may become too high, resulting in a risk of reduced processability (workability in friction treatment).

[0050] (C) Non-reinforcing filler The rubber composition for reinforcing fabric may further contain a non-reinforcing filler (C) in order to achieve both workability and abrasion resistance without impairing economic efficiency.

[0051] Examples of non-reinforcing fillers (C) include polyvalent metal carbonates (calcium carbonate, magnesium carbonate, etc.), polyvalent metal hydroxides (aluminum hydroxide, etc.), polyvalent metal sulfates (calcium sulfate, barium sulfate, etc.), silicates (natural or synthetic silicates in which part of the silicon is substituted with a polyvalent metal atom, such as aluminum silicate, magnesium silicate, aluminum magnesium silicate, and calcium silicate; minerals containing silicate as the main component, for example, silicate minerals such as clay containing aluminum silicate, talc containing magnesium silicate, and mica), lithopone, silica sand, etc. These non-reinforcing fillers can be used alone or in combination of two or more.

[0052] Of these, calcium carbonate, magnesium silicate or talc containing magnesium silicate, and aluminum silicate or clay containing aluminum silicate are preferred, calcium carbonate and clay are more preferred, and calcium carbonate is particularly preferred from the viewpoint of an excellent balance between workability, abrasion resistance, and economy.

[0053] The average particle size (average primary particle size) of the non-reinforcing filler (C) is, for example, 0.01 to 25 μm, preferably 0.1 to 20 μm, further preferably 0.3 to 15 μm, even more preferably 0.5 to 5 μm, and most preferably 1 to 3 μm. If the average particle size of the non-reinforcing filler (C) is too small, workability may decrease, whereas if it is too large, abrasion resistance may decrease.

[0054] In the present application, the average particle size of the non-reinforcing filler can be measured as a volume average particle size using a laser diffraction particle size distribution measuring device.

[0055] The proportion of the non-reinforcing filler (C) is, for example, 5 to 100 parts by mass, preferably 8 to 50 parts by mass, further preferably 10 to 45 parts by mass, further preferably 20 to 40 parts by mass, and most preferably 25 to 35 parts by mass, relative to 100 parts by mass of the rubber component (A). If the proportion of the non-reinforcing filler (C) is too low, it may be difficult to balance workability, abrasion resistance, and economy, whereas if it is too high, Vm may increase, resulting in a decrease in workability.

[0056] (D) Adhesion improver The rubber composition for reinforcing fabric may further contain an adhesion improver (D) in order to improve the adhesion and abrasion resistance of the reinforcing fabric.

[0057] Examples of the adhesion improver (D) include, as a resin component, phenolic resins [such as resorcinol-formaldehyde co-condensates (RF condensates)], amino resins [such as melamine resins like hexamethylol melamine, hexaalkoxymethyl melamine (hexamethoxymethyl melamine, hexabutoxymethyl melamine), etc.; urea resins like methylol urea; benzoguanamine resins like methylol benzoguanamine resins], epoxy compounds, isocyanate compounds, etc. These adhesion improvers can be used alone or in combination of two or more.

[0058] Of these resin components, phenol resins and amino resins are preferred, and melamine resins are particularly preferred, as they can improve the adhesiveness and abrasion resistance of the reinforcing fabric.

[0059] The adhesion improver (D) may be a combination of the resin component and silica.

[0060] Silica includes dry silica, wet silica, surface-treated silica, etc. Silica can also be classified into dry-process white carbon, wet-process white carbon, colloidal silica, precipitated silica, etc., depending on the production method. Silica may be amorphous silica. These silicas can be used alone or in combination. Among these silicas, silicas having surface silanol groups (silicic anhydride, silicic acid hydrate) are preferred, and silicic acid hydrates with many surface silanol groups have a strong chemical bond with rubber components.

[0061] The average particle size (average primary particle size) of silica is, for example, 1 to 500 nm, preferably 3 to 300 nm, further preferably 5 to 100 nm, and even more preferably 10 to 50 nm.

[0062] In the present application, the average particle size of silica can be measured using, for example, a scanning electron microscope or a transmission electron microscope, and the arithmetic average particle size can be calculated for an appropriate number of samples (for example, 50 samples) by image analysis.

[0063] The nitrogen adsorption specific surface area of ​​silica by the BET method is, for example, 50 to 400 m 2 / g, preferably 100 to 300m 2 / g, more preferably 150 to 200m 2 / g.

[0064] The proportion of silica may be, for example, 10 to 100 parts by mass, preferably 30 to 80 parts by mass, more preferably 40 to 70 parts by mass, and most preferably 50 to 60 parts by mass, relative to 100 parts by mass of the resin component.

[0065] The proportion of the adhesion improver (D) is, for example, 0.1 to 10 parts by mass, preferably 0.5 to 8 parts by mass, further preferably 1 to 5 parts by mass, even more preferably 2 to 4 parts by mass, and most preferably 2.5 to 3.5 parts by mass, relative to 100 parts by mass of the rubber component (A). If the proportion of the adhesion improver (D) is too low, the effect of improving the adhesion and abrasion resistance of the reinforcing fabric may decrease, whereas if it is too high, workability may decrease.

[0066] (E) Tackifier The reinforcing fabric rubber composition may further contain a tackifier (E) to increase the tackiness (stickiness) of the uncrosslinked rubber composition and improve workability. In particular, when the friction transmission belt is a wrapped V-belt, if the uncrosslinked rubber composition contains a tackifier (E), it becomes easier to hold the reinforcing fabric precursor wound around the outer periphery of the belt, thereby improving belt productivity.

[0067] Examples of the tackifier (E) include factice [sulfur factice (black sub) obtained by crosslinking fats and oils (vegetable oils such as linseed oil, rapeseed oil, castor oil, cottonseed oil, and soybean oil) with sulfur or hydrogen sulfide, sulfur chloride factice (white sub) obtained by crosslinking the fats and oils with sulfur monochloride or sulfur dichloride, and sulfur-free factice obtained by crosslinking the fats and oils with an isocyanate compound or an organic peroxide], terpene resins (polyterpene resins or hydrogenated products thereof, terpene phenolic resins or hydrogenated products thereof), rosin resins (natural rosin, hardened rosin, disproportionated rosin, polymerized rosin, rosin ester, rosin phenolic resin, and the like), petroleum resins (C 5-9 Examples of tackifiers include aliphatic petroleum resins primarily composed of higher olefin hydrocarbons such as distillates, dicyclopentadiene petroleum resins primarily composed of dicyclopentadiene or hydrogenated products thereof, aromatic petroleum resins primarily composed of aromatic hydrocarbons such as vinyltoluene or indene or hydrogenated products thereof, coumarone resins such as coumarone-indene resins and coumarone-indene-styrene copolymers or hydrogenated products thereof, and modified olefin polymers [ethylene-(meth)acrylic acid copolymer, ethylene-2-hydroxyethyl (meth)acrylate copolymer, ethylene-glycidyl (meth)acrylate copolymer, ethylene-vinyl acetate-(meth)acrylic acid copolymer, ethylene-ethyl (meth)acrylate-maleic anhydride copolymer, partially saponified ethylene-vinyl acetate copolymer, etc.]. These tackifiers can be used alone or in combination of two or more.

[0068] Of these, factices (vulcanized fats and oils or subs) such as sulfur factice, and petroleum resins such as coumarone resins are preferred, and a combination of factice and petroleum resin is particularly preferred.

[0069] When combining factice with petroleum resin, the proportion of factice can be selected from the range of about 5 to 1000 parts by mass per 100 parts by mass of petroleum resin, for example, 10 to 100 parts by mass, preferably 20 to 80 parts by mass, and more preferably 30 to 50 parts by mass.

[0070] The proportion of the tackifier (E) is, for example, 1 to 50 parts by mass, preferably 5 to 30 parts by mass, further preferably 7 to 25 parts by mass, further preferably 8 to 20 parts by mass, and most preferably 10 to 15 parts by mass, relative to 100 parts by mass of the rubber component (A). If the proportion of the tackifier (E) is too low, the effect of improving workability may decrease, whereas if it is too high, the abrasion resistance may decrease.

[0071] (F) Crosslinker The rubber composition for reinforcing fabric may further contain a crosslinking agent (F). Examples of crosslinking agents (F) include metal oxides (magnesium oxide, zinc oxide, lead oxide, etc.), sulfur-based crosslinking agents (powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, sulfur chlorides (sulfur monochloride, sulfur dichloride, etc.)), oximes (quinone dioxime, etc.), guanidines (diphenyl guanidine, etc.), and organic peroxides (diacyl peroxides, peroxy esters, dialkyl peroxides (e.g., dicumyl peroxide, t-butylcumyl peroxide, 1,1-di-butylperoxy-3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di(t-butylperoxy)-hexane, 1,3-bis(t-butylperoxy-isopropyl)benzene, di-t-butyl peroxide, etc.). These crosslinking agents can be used alone or in combination.

[0072] When the rubber component (A) is a chloroprene rubber, a metal oxide (magnesium oxide, zinc oxide, etc.) may be used as the crosslinking agent (F). The metal oxide may be used in combination with another crosslinking agent (sulfur-based crosslinking agent, etc.).

[0073] The proportion of the crosslinking agent (F) is, for example, 1 to 20 parts by mass, preferably 5 to 15 parts by mass, and more preferably 8 to 12 parts by mass, calculated as solid content, per 100 parts by mass of the rubber component (A), depending on the type of the rubber component (A).

[0074] The proportion of the metal oxide as the crosslinking agent (F) is, for example, 1 to 20 parts by mass, preferably 3 to 17 parts by mass, more preferably 5 to 15 parts by mass, and even more preferably 7 to 13 parts by mass, per 100 parts by mass of the rubber component (A). When a metal oxide and a sulfur-based crosslinking agent are combined as the crosslinking agent (F), the proportion of the sulfur-based crosslinking agent is, for example, 0.1 to 50 parts by mass, preferably 1 to 30 parts by mass, and even more preferably 3 to 20 parts by mass, per 100 parts by mass of the metal oxide. The proportion of the organic peroxide is, for example, 1 to 8 parts by mass, preferably 1.5 to 5 parts by mass, and even more preferably 2 to 4.5 parts by mass, per 100 parts by mass of the rubber component (A). If the proportion of the crosslinking agent (F) is too low, abrasion resistance may decrease, and if it is too high, workability may decrease.

[0075] (G) Co-agent (crosslinking aid or co-vulcanizing agent) The rubber composition for reinforcing fabric may further contain a co-crosslinking agent (G) to improve abrasion resistance. In particular, by combining it with carbon black (B), the proportion of carbon black (B) can be reduced to ensure workability and improve abrasion resistance.

[0076] Examples of the co-crosslinking agent (G) include bismaleimide compounds [aliphatic bismaleimides such as N,N'-1,2-ethylenedimaleimide and 1,6'-bismaleimide-(2,2,4-trimethyl)cyclohexane; aromatic bismaleimides such as N,N'-m-phenylenedimaleimide, 4-methyl-1,3-phenylenedimaleimide, 4,4'-diphenylmethanedimaleimide, 2,2-bis[4-(4-maleimidophenoxy)phenyl]propane, 4,4'-diphenyletherdimaleimide, 4,4'-diphenylsulfonedimaleimide, and 1,3-bis(3-maleimidophenoxy)benzene]; Examples of suitable co-crosslinking agents include bismaleimide, polyfunctional (iso)cyanurates (such as triallyl isocyanurate (TAIC) and triallyl cyanurate (TAC)), polydienes (such as 1,2-polybutadiene), metal salts of α,β-unsaturated carboxylic acids (such as zinc (meth)acrylate and magnesium (meth)acrylate), oximes (such as quinone dioximes), guanidines (such as diphenyl guanidine), and polyfunctional (meth)acrylates (such as ethylene glycol di(meth)acrylate, butanediol di(meth)acrylate, and trimethylolpropane tri(meth)acrylate). These co-crosslinking agents (G) can be used alone or in combination. The co-crosslinking agent may be selected appropriately depending on the type of crosslinking agent (F).

[0077] Of these, bismaleimide compounds are preferred, and aromatic bismaleimides (arene bismaleimides) such as N,N'-m-phenylenedimaleimide are particularly preferred because they can improve wear resistance.

[0078] The proportion of the co-crosslinking agent (G) is, for example, 0.1 to 5 parts by mass, preferably 0.3 to 3 parts by mass, further preferably 0.5 to 2.5 parts by mass, further preferably 0.7 to 2 parts by mass, and most preferably 0.8 to 1.5 parts by mass, relative to 100 parts by mass of the rubber component (A). If the proportion of the co-crosslinking agent (G) is too low, the effect of improving abrasion resistance may decrease, whereas if it is too high, Vm may increase, resulting in a decrease in workability.

[0079] (H) Plasticizer The rubber composition for reinforcing fabric may further contain a plasticizer (H) to improve workability. Examples of the plasticizer (H) include oil-based plasticizers (paraffinic oils, alicyclic oils (naphthenic oils), aromatic oils, etc.), aliphatic carboxylic acid-based plasticizers (adipate ester-based plasticizers, sebacic acid ester-based plasticizers, etc.), aromatic carboxylic acid ester-based plasticizers (phthalate ester-based plasticizers, trimellitic acid ester-based plasticizers, etc.), oxycarboxylic acid ester-based plasticizers, phosphate ester-based plasticizers, ether-based plasticizers, and ether ester-based plasticizers. These plasticizers can be used alone or in combination. Of these, oil-based plasticizers are preferred, and alicyclic oils are particularly preferred.

[0080] The proportion of the plasticizer (H) relative to 100 parts by mass of the rubber component is, for example, 1 to 80 parts by mass, preferably 5 to 50 parts by mass, further preferably 10 to 40 parts by mass, further preferably 15 to 35 parts by mass, and most preferably 20 to 30 parts by mass. If the proportion of the plasticizer (H) is too low, the effect of improving workability may decrease, whereas if it is too high, the abrasion resistance may decrease.

[0081] (I) Other additives The rubber composition for reinforcing fabric may further contain, as other additives (I), conventional additives that are compounded in rubber.

[0082] Examples of commonly used additives include processing agents or processing aids (fatty acids or metal salts thereof such as stearic acid and metal stearates; fatty acid esters such as stearic acid esters; fatty acid amides such as stearic acid amide), antioxidants (antioxidants, heat-aging inhibitors, flex crack inhibitors, antiozonants, etc.), crosslinking accelerators, crosslinking retarders, colorants, coupling agents (silane coupling agents, etc.), stabilizers (ultraviolet absorbers, heat stabilizers, etc.), lubricants, flame retardants, antistatic agents, etc. These additives can be used alone or in combination of two or more.

[0083] Among these, processing agents or processing aids, anti-aging agents, etc. are commonly used.

[0084] The total proportion of the other additives (I) relative to 100 parts by mass of the rubber component (A) is, for example, 0.01 to 30 parts by mass, preferably 0.1 to 20 parts by mass, further preferably 1 to 15 parts by mass, and even more preferably 3 to 10 parts by mass.

[0085] (J) Metal particles and ceramic particles The rubber composition for reinforcing fabric preferably contains substantially no metal particles, and particularly preferably does not contain any metal particles. Unlike Patent Document 2, the present invention can improve abrasion resistance even if the rubber composition for reinforcing fabric does not substantially contain metal particles, thereby improving economic efficiency. Furthermore, a rubber composition for reinforcing fabric that does not substantially contain metal particles can suppress an increase in Vm, thereby improving workability.

[0086] The rubber composition for reinforcing fabric preferably does not substantially contain ceramic particles as a reinforcing agent, and particularly preferably does not contain ceramic particles as a reinforcing agent. Unlike Patent Document 1, the present invention can improve abrasion resistance even if the rubber composition for reinforcing fabric does not substantially contain ceramic particles, thereby improving economic efficiency. Furthermore, a rubber composition for reinforcing fabric that does not substantially contain ceramic particles can suppress an increase in Vm, thereby improving workability.

[0087] (fabric) Examples of fabrics include woven fabrics, knitted fabrics (weft-knitted fabrics and warp-knitted fabrics), nonwoven fabrics, etc. Among these, woven fabrics woven in a plain weave, twill weave, satin weave, etc., and woven fabrics and knitted fabrics woven at a wide angle between the warp and weft threads exceeding 90° and not exceeding 120° are preferred, and woven fabrics commonly used as cover fabrics for transmission belts for general industrial and agricultural machinery [plain weave fabrics in which the warp and weft threads cross at a right angle, and plain weave fabrics (wide-angle canvas) in which the warp and weft threads cross at a wide angle between the warp and weft threads exceeding 90° and not exceeding 120°] are particularly preferred.

[0088] Commonly used fibers for fabrics include synthetic fibers such as polyolefin fibers (polyethylene fibers, polypropylene fibers, etc.), polyamide fibers (polyamide 6 fibers, polyamide 66 fibers, polyamide 46 fibers, aramid fibers, etc.), polyester fibers (polyalkylene arylate fibers such as polyethylene terephthalate (PET) fibers and polyethylene naphthalate (PEN) fibers), vinyl alcohol fibers (polyvinyl alcohol, ethylene-vinyl alcohol copolymer fibers, vinylon fibers, etc.), and polyparaphenylene benzobisoxazole (PBO) fibers; cellulose fibers (cellulose fibers, cellulose derivative fibers, etc.), natural fibers such as wool; and inorganic fibers such as carbon fibers. These fibers may be used alone as a single yarn or may be combined to form a blended yarn of two or more types.

[0089] Among these fibers, cellulosic fibers are preferred because they are easy to support the rubber composition and are economical. Composite yarns (particularly blended yarns) of cellulosic fibers and synthetic fibers are particularly preferred because they are economical and have excellent abrasion resistance. From an economical standpoint, the proportion of cellulosic fibers may be 50% by mass or more of the total fibers, preferably 80% by mass or more, more preferably 90% by mass or more, or even 100% by mass. From an economical standpoint and abrasion resistance, the proportion of cellulosic fibers may be 10% by mass or more of the total fibers, for example, 10 to 80% by mass, preferably 20 to 50% by mass, and more preferably 30 to 40% by mass.

[0090] Cellulose-based fibers include cellulose fibers (cellulose fibers derived from plants, animals, bacteria, etc.) and cellulose derivative fibers. Examples of cellulose fibers include cellulose fibers (pulp fibers) derived from natural plants such as wood pulp (softwood, hardwood pulp, etc.), bamboo fiber, sugarcane fiber, seed hair fibers (cotton fiber (cotton linter), kapok, etc.), algae fiber (Manila hemp, New Zealand hemp, etc.), animal-derived cellulose fibers such as sea squirt cellulose, bacterial cellulose fiber, and algae cellulose. Examples of cellulose derivative fibers include cellulose ester fibers and regenerated cellulose fibers (rayon, cupra, lyocell, etc.).

[0091] In the composite yarn of cellulosic fiber and synthetic fiber, the synthetic fiber is preferably a polyolefin fiber, a polyamide fiber, or a polyester fiber, and particularly preferably a polyester fiber. The polyester fiber may be a polyalkylene arylate fiber. Examples of the polyalkylene arylate fiber include poly-C fibers such as PET fiber, polybutylene terephthalate (PBT) fiber, and PEN fiber. 2-4 Alkylene-C 8-14 Examples include arylate fibers.

[0092] In a composite yarn of cellulosic fiber and synthetic fiber, the mass ratio of cellulosic fiber to synthetic fiber (particularly polyester fiber) is, for example, former / latter = 90 / 10 to 10 / 90, preferably 80 / 20 to 15 / 85, further preferably 70 / 30 to 20 / 80, further preferably 50 / 50 to 25 / 75, and most preferably 40 / 60 to 30 / 70. If the proportion of cellulosic fiber is too low, the effect of improving economic efficiency may be reduced, and conversely, if it is too high, the effect of improving abrasion resistance may be reduced.

[0093] The average fineness of the fibers constituting the fabric is, for example, about 5 to 30 count, preferably about 10 to 25 count, and more preferably about 10 to 20 count. If the fineness (count) is too small, it may be difficult to uniformly penetrate the rubber composition between the fibers, and if it is too large, the mechanical strength of the reinforcing fabric may decrease.

[0094] The basis weight of the fabric (raw fabric) is, for example, 100 to 500 g / m 2 , preferably 200 to 400 g / m 2 , and more preferably 250 to 350 g / m 2 If the weight per unit area is too large, the flexibility of the belt may be reduced, and if it is too small, the reinforcing effect of the reinforcing fabric may be reduced.

[0095] When the fabric (raw fabric) is a woven fabric, the thread density (density of warp and weft threads) of the fabric is, for example, about 60 to 100 threads / 50 mm, preferably about 70 to 90 threads / 50 mm, and more preferably about 75 to 85 threads / 50 mm. If the density is too high, it may be difficult to uniformly penetrate the rubber composition between the fibers, and conversely, if the density is too low, the amount of rubber composition attached may increase, resulting in reduced abrasion resistance.

[0096] The fabric may be subjected to an adhesive treatment (for example, an adhesive treatment such as immersion in resorcinol-formalin-latex liquid (RFL liquid)).

[0097] The fabric may be single layer or multi-layer (for example, 2 to 5 layers, preferably 2 to 4 layers, and more preferably 2 to 3 layers), but from the standpoint of productivity, a single layer (1 ply) or two layers (2 ply) is preferred, and two layers is particularly preferred.

[0098] (Characteristics of reinforcing fabric) The proportion of the rubber composition for the reinforcing fabric can be selected from a range of about 5 to 80% by mass in the reinforcing fabric. Because the fabric and the rubber composition mutually reinforce each other and improve abrasion resistance, it is, for example, 10 to 70% by mass, preferably 20 to 60% by mass, more preferably 25 to 55% by mass, even more preferably 30 to 50% by mass, and most preferably 35 to 45% by mass. If the proportion of the rubber composition is too low, the fabric may be easily exposed, resulting in reduced abrasion resistance (the fabric may be more susceptible to abrasion). On the other hand, if the proportion is too high, there may be a large amount of "free and weak" rubber composition that is not incorporated into the weave of the fabric, resulting in reduced abrasion resistance (the rubber may be more susceptible to abrasion).

[0099] The reinforcing fabric may have at least one surface thereof friction-treated with the rubber composition for the reinforcing fabric, but it is preferred that both surfaces (front and back) of the reinforcing fabric be friction-treated with the rubber composition for the reinforcing fabric. Friction-treating both surfaces of the reinforcing fabric with the rubber composition for the reinforcing fabric makes it easier to achieve both workability and abrasion resistance, and in particular, when the fabric is multi-layered, it can improve the tackiness when the friction-treated fabric is wound in multiple layers and the adhesion between the friction-treated fabrics.

[0100] The average thickness of the reinforcing fabric (in the case of a multi-layer structure, the total average thickness of all the layers) is, for example, 0.4 to 2 mm, preferably 0.5 to 1.4 mm, and more preferably 0.6 to 1.2 mm. If the reinforcing fabric is too thin, the abrasion resistance may decrease, and if it is too thick, the flexibility of the belt may decrease.

[0101] In this specification and claims, the average thickness of the reinforcing fabric can be measured based on a scanning electron microscope (SEM) photograph, and is calculated as the average value of values ​​at any five or more points by image analysis or the like.

[0102] [Belt body] The belt body typically includes a compression rubber layer, a core layer, and a tension rubber layer. Depending on the type of belt, a tension layer may be formed using a backing fabric instead of the tension rubber layer. Meanwhile, the adhesive rubber layer is not an essential layer in the belt body, and the belt may be configured either to include an adhesive rubber layer or not to include an adhesive rubber layer.

[0103] (Compressed rubber layer) The compressed rubber layer is formed of a rubber composition containing the rubber component (a) (rubber composition for the compressed rubber layer). The average thickness of the compressed rubber layer can be appropriately selected depending on the type of belt, and is, for example, 1 to 30 mm, preferably 1.5 to 25 mm, and more preferably 2 to 20 mm.

[0104] (a) Rubber component Examples of the rubber component (a) include the rubber components exemplified in the section on rubber component (A), etc. The rubber components can be used alone or in combination of two or more.

[0105] Among the rubber components, diene rubber is preferred, and a combination of natural rubber and styrene-butadiene rubber is preferred. The mass ratio of the natural rubber to the styrene-butadiene rubber is 1 / 99 to 90 / 10, preferably 5 / 95 to 80 / 20, more preferably 10 / 90 to 50 / 50, and even more preferably 20 / 80 to 30 / 70.

[0106] The proportion of the rubber component (a) in the rubber composition for the compressed rubber layer is 20 to 80 mass %, preferably 30 to 75 mass %, further preferably 40 to 70 mass %, further preferably 45 to 65 mass %, and most preferably 50 to 60 mass %.

[0107] (b) Carbon black The rubber composition for the compressed rubber layer may further contain carbon black (b). The average particle size and iodine adsorption capacity of the carbon black (b), including preferred embodiments, can be selected from the ranges of the average particle size and iodine adsorption capacity described in the section on carbon black (B).

[0108] The proportion of carbon black (b) relative to 100 parts by mass of the rubber component (a) is, for example, 10 to 100 parts by mass, preferably 30 to 80 parts by mass, further preferably 40 to 70 parts by mass, even more preferably 45 to 65 parts by mass, and most preferably 50 to 60 parts by mass.

[0109] (c) Crosslinking agent The rubber composition for the compressed rubber layer may further contain a crosslinking agent (c). The crosslinking agent (c), including preferred embodiments thereof, can be selected from the crosslinking agents described in the section on crosslinking agent (F). The proportion of the crosslinking agent (c) is, for example, 1 to 15 parts by mass, preferably 3 to 13 parts by mass, and more preferably 5 to 10 parts by mass, per 100 parts by mass of the rubber component (a). The proportion of the metal oxide as the crosslinking agent (c) is, for example, 1 to 15 parts by mass, preferably 2 to 10 parts by mass, and more preferably 3 to 8 parts by mass, per 100 parts by mass of the rubber component (a). When a metal oxide and a sulfur-based crosslinking agent are combined as the crosslinking agent (c), the proportion of the sulfur-based crosslinking agent is, for example, 10 to 100 parts by mass, preferably 30 to 70 parts by mass, and more preferably 40 to 60 parts by mass, per 100 parts by mass of the metal oxide.

[0110] (d) Crosslinking accelerator The rubber composition for the compressed rubber layer may further contain a crosslinking accelerator (d). Examples of the crosslinking accelerator (d) include thiuram accelerators [e.g., tetramethylthiuram monosulfide (TMTM), tetramethylthiuram disulfide (TMTD), tetraethylthiuram disulfide (TETD), tetrabutylthiuram disulfide (TBTD), dipentamethylenethiuram tetrasulfide (DPTT), N,N'-dimethyl-N,N'-diphenylthiuram disulfide, etc.], sulfenamide accelerators [e.g., N-cyclohexyl-2-benzothiazylsulfenamide (CBS), N,N'-dicyclohexyl-2-benzothiazylsulfenamide, Nt-butyl-2-benzothiazylsulfenamide (TBBS)], thiomorpholine accelerators [e.g., 4,4'-dithiodimorpholine (DTDM), 2-(4'-morpholinodithio)benzothiazol- azoles, etc.), thiazole-based accelerators [e.g., 2-mercaptobenzothiazole (MBT), zinc salt of MBT, 2-mercaptobenzothiazoledibenzothiazyl disulfide (MBTS), 2-mercaptothiazoline, dibenzothiazyl disulfide, 2-(4'-morpholinodithio)benzothiazole, etc.], urea- or thiourea-based accelerators [e.g., ethylenethiourea, trimethylthiourea (TMU), diethylthiourea (EDE)], guanidine-based accelerators (diphenylguanidine, di-o-tolylguanidine), dithiocarbamate-based accelerators [e.g., sodium dimethyldithiocarbamate, zinc diethyldithiocarbamate (EZ), zinc dibutyldithiocarbamate (BZ)], xanthate-based accelerators (e.g., zinc isopropylxanthate), etc. These crosslinking accelerators may be used alone or in combination.

[0111] Of these crosslinking accelerators, TMTD, DPTT, CBS, MBTS, etc. are commonly used, and thiazole accelerators such as MBTS are preferred.

[0112] The proportion of the crosslinking accelerator (d) relative to 100 parts by mass of the rubber component (a) is, for example, 0.1 to 5 parts by mass, preferably 0.2 to 4 parts by mass, further preferably 0.3 to 3 parts by mass, even more preferably 0.5 to 2.5 parts by mass, and most preferably 1 to 2 parts by mass.

[0113] (e) Plasticizers The rubber composition for the compressed rubber layer may further contain a plasticizer (e). Examples of the plasticizer (e) include the plasticizers exemplified in the section on plasticizer (H). The plasticizers can be used alone or in combination of two or more. Among the plasticizers, oil-based plasticizers are preferred, and aromatic oils are particularly preferred.

[0114] The proportion of the plasticizer (e) relative to 100 parts by mass of the rubber component (a) is, for example, 1 to 50 parts by mass, preferably 3 to 30 parts by mass, further preferably 5 to 25 parts by mass, and even more preferably 10 to 20 parts by mass.

[0115] (f) Other additives The rubber composition for the compressed rubber layer may further contain, as other additives (f), conventional additives that are blended into rubber. Examples of conventional additives include those exemplified in the section on other additives (I), as well as short fibers (cellulose-based fibers such as cotton and rayon, polyester fibers such as polyethylene terephthalate fibers, and polyamide fibers such as nylon fibers and aramid fibers), fillers (metal oxides such as calcium oxide, barium oxide, iron oxide, copper oxide, titanium oxide, and aluminum oxide; metal carbides such as silicon carbide and tungsten carbide; metal nitrides such as titanium nitride, aluminum nitride, and boron nitride; and mineral materials such as zeolite, diatomaceous earth, calcined diatomaceous earth, activated clay, alumina, mica, kaolin, sericite, bentonite, montmorillonite, smectite, and clay). The total proportion of the other additives (f) relative to 100 parts by mass of the rubber component (a) is, for example, 0.01 to 100 parts by mass, preferably 0.1 to 50 parts by mass, further preferably 1 to 30 parts by mass, and even more preferably 2 to 10 parts by mass.

[0116] (Tension rubber layer) The rubber composition forming the tension rubber layer (rubber composition for tension rubber layer) may be a different rubber composition from the rubber composition for the compression rubber layer, or may be the same rubber composition. From the viewpoint of productivity, the rubber composition for the compression rubber layer and the rubber composition for the tension rubber layer are preferably the same rubber composition. Even if the rubber composition for the tension rubber layer is a different rubber composition from the rubber composition for the compression rubber layer, it is preferably a rubber composition selected from the preferred embodiments of the rubber composition for the compression rubber layer.

[0117] The average thickness of the tension rubber layer can be appropriately selected depending on the type of belt, and is, for example, 0.5 to 10 mm, preferably 0.6 to 5 mm, and more preferably 0.6 to 2 mm.

[0118] (Adhesive rubber layer) The rubber composition for forming the adhesive rubber layer (rubber composition for adhesive rubber layer) is not particularly limited as long as it is a composition having enhanced adhesive function compared to the rubber composition for compressed rubber layer. From the viewpoint of improving the adhesion between layers, the rubber composition for adhesive rubber layer is preferably a rubber composition obtained by adding a tackifier (g) to the composition of the rubber composition for compressed rubber layer and adjusting the composition ratio.

[0119] Examples of the tackifier (g) include the tackifiers exemplified in the section on tackifier (E). The tackifiers can be used alone or in combination of two or more. Among the tackifiers, petroleum resins are preferred.

[0120] The proportion of the tackifier (g) relative to 100 parts by mass of the rubber component is, for example, 0.1 to 30 parts by mass, preferably 0.3 to 10 parts by mass, further preferably 0.5 to 5 parts by mass, and even more preferably 1 to 3 parts by mass.

[0121] The composition ratio may be adjusted by adjusting the proportions of carbon black, crosslinking agent, and crosslinking accelerator.

[0122] The amount of carbon black is, for example, 30 to 100 parts by mass, preferably 50 to 80 parts by mass, further preferably 55 to 75 parts by mass, and even more preferably 60 to 70 parts by mass, per 100 parts by mass of the rubber component.

[0123] The proportion of the crosslinking agent is, for example, 1 to 12 parts by mass, preferably 2 to 10 parts by mass, and more preferably 3 to 8 parts by mass, relative to 100 parts by mass of the rubber component. When a metal oxide and a sulfur-based crosslinking agent are combined as the crosslinking agent, the proportion of the sulfur-based crosslinking agent is, for example, 3 to 50 parts by mass, preferably 5 to 40 parts by mass, and more preferably 10 to 30 parts by mass, relative to 100 parts by mass of the metal oxide.

[0124] The proportion of the crosslinking accelerator relative to 100 parts by mass of the rubber component is, for example, 0.1 to 4 parts by mass, preferably 0.2 to 3 parts by mass, further preferably 0.3 to 2 parts by mass, and even more preferably 0.5 to 1.5 parts by mass.

[0125] The average thickness of the adhesive rubber layer can be appropriately selected depending on the type of belt, etc., and is, for example, 0.2 to 5 mm, preferably 0.3 to 3 mm, and more preferably 0.5 to 2 mm.

[0126] (Core layer) The core body is not particularly limited, but typically, a core wire (twisted cord) arranged at a predetermined interval in the width direction of the belt can be used. The core wires are arranged to extend in the length direction of the belt, and may be arranged in parallel with the length direction of the belt at a predetermined pitch. However, from the viewpoint of productivity, they are usually arranged in a spiral shape, extending in parallel with the length direction of the belt at a predetermined pitch. When arranged in a spiral shape, the angle of the core wire with respect to the length direction of the belt may be, for example, 5° or less, and from the viewpoint of belt running performance, the closer to 0° the angle is, the more preferable. Furthermore, the pitch or interval, which is the distance between the centers of adjacent core bodies (particularly the spinning pitch of the core wire), is preferably set in the range of 1.5 to 2.5 mm, and more preferably in the range of 1.8 to 2.2 mm.

[0127] The fibers constituting the core wire include, for example, C fibers such as ethylene terephthalate and ethylene-2,6-naphthalate. 2-4 Alkylene-C 8-14 Polyester fibers (polyalkylene arylate fibers) having arylate as the main structural unit, synthetic fibers such as aramid fibers, and inorganic fibers such as carbon fibers are commonly used, with polyester fibers (polyethylene terephthalate fibers, polyethylene naphthalate fibers, etc.) and aramid fibers being preferred, and polyester fibers being particularly preferred.

[0128] These fibers may be used as multifilament yarns in which a large number of fibers (filaments) are aligned. The number of filaments contained in the multifilament yarn may be, for example, 100 to 5000, preferably 200 to 3000, and more preferably 300 to 1000. The fineness of the multifilament yarn may be, for example, 100 to 2000 dtex, preferably 300 to 1700 dtex, and more preferably 500 to 1250 dtex.

[0129] The core wire can usually be a twisted cord (e.g., double twist, single twist, Lang twist, etc.) using multifilament yarn. The average wire diameter of the core wire (diameter of the twisted cord) may be, for example, 0.5 to 3 mm, preferably 0.6 to 2.5 mm, and more preferably 0.7 to 2 mm. The total fineness of the core wire (twisted cord) may be, for example, 2,000 to 30,000 dtex, preferably 5,000 to 25,000 dtex, and more preferably 10,000 to 20,000 dtex. The number of filaments contained in the core wire (twisted cord) may be, for example, 2,000 to 20,000, preferably 3,000 to 12,000, and more preferably 5,000 to 8,000.

[0130] The core wire may be subjected to an adhesive treatment (or surface treatment) using a conventional method (such as an adhesive treatment using an RFL liquid, an epoxy compound, an isocyanate compound, or the like) to improve adhesion to the rubber component.

[0131] [Manufacturing method of friction transmission belt] The friction transmission belt of the present invention is obtained through a friction process in which at least one surface of a fabric is friction-treated with the reinforcing fabric rubber composition containing an uncrosslinked rubber component to produce a reinforcing fabric precursor. That is, in the friction process, a specific rubber composition is used to adjust the Mooney scorch minimum viscosity and rubber hardness Hs of the rubber composition. In addition, since the present invention uses friction as a method for producing a reinforcing fabric, unlike methods such as soaking and surface coating, it does not require a drying step using a solvent, which reduces the environmental impact. Furthermore, with methods in which a sheet-like rubber composition is laminated, it is difficult to reduce the sheet thickness and to sufficiently penetrate the rubber composition between the fibers, making it difficult to improve adhesion and abrasion resistance. In contrast, friction allows the rubber composition to efficiently penetrate between the fibers, thereby reducing the amount of rubber composition used and improving adhesion and abrasion resistance.

[0132] In the friction step, a friction method (friction) is used in which the rubber composition for reinforcing fabric is rubbed into at least one surface of the fabric. In the friction method, for example, a calender roll may be used to simultaneously pass a solid composition (such as an uncrosslinked rubber composition) and the fabric between rolls rotating at different speeds, thereby applying pressure (squeezing) and rubbing the solid composition into the fibers of the fabric. The shape of the rubber composition for reinforcing fabric is not particularly limited, but it may be in the form of a sheet so that it can be uniformly imprinted onto the fabric. The friction treatment may be performed once on the front surface and once on the back surface.

[0133] The reinforcing fabric precursor obtained in the friction step is subjected to a conventional crosslinking step for producing a friction transmission belt. In the crosslinking step, at least a portion of the surface of the belt body precursor is covered with the reinforcing fabric precursor and crosslinked to firmly integrate the belt body and the reinforcing fabric, and the crosslinking step can be carried out by a known or conventional method except for the use of the reinforcing fabric. The crosslinking temperature can be selected depending on the type of rubber component and is, for example, 120 to 200°C, preferably 150 to 180°C.

[0134] A conventional method can be used to manufacture a belt body precursor depending on the type of belt. For example, in the case of a wrapped V-belt, a wrapped V-belt can be obtained by cutting an uncrosslinked compression rubber layer sheet obtained by rolling and setting it on a mantle, wrapping a core around it, and further wrapping an uncrosslinked tension rubber layer sheet around the wrapped core. The resulting annular laminate can be cut (sliced) on the mantle. Finally, the cut annular laminate can be placed over a pair of pulleys and cut into a V-shape while rotating. The resulting belt body precursor can then be wrapped with the reinforcing fabric precursor and subjected to a crosslinking process. For example, methods described in JP-A-6-137381 and WO2015 / 104778 can also be used to manufacture such wrapped V-belts. [Example]

[0135] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Details of the materials used in the examples are shown below.

[0136] [Raw materials for rubber compositions] Chloroprene rubber: Denka Co., Ltd. "PM-40" Natural rubber: SVR20 (standard Vietnamese rubber) SBR: "Nipol1502" manufactured by Nippon Zeon Co., Ltd. Magnesium oxide: Kyowa Mag 150 manufactured by Kyowa Chemical Co., Ltd. Zinc oxide: Sakai Chemical Industry Co., Ltd. "Zinc oxide type 2" Plasticizer A (naphthenic oil): "SUNTHENE 410" manufactured by Japan Sun Oil Co., Ltd. Plasticizer B (aromatic oil): Idemitsu Kosan Co., Ltd. "Diana Process Oil AH-16" Tackifier A: "Black Sub 21" manufactured by Tenma Sub Chemical Co., Ltd. Tackifier B: "Coumarone Indene Oil" manufactured by Kobe Oil Chemical Industry Co., Ltd. Tackifier C: ExxonMobil "ESCOLETZ 1102" Carbon black SRF: "Seast S" manufactured by Tokai Carbon Co., Ltd., average primary particle diameter 66 nm Carbon black HAF: "Seast 3" manufactured by Tokai Carbon Co., Ltd., average primary particle size 28 nm Carbon black GPF: "HTC#G" manufactured by Nippon Steel Carbon Co., Ltd. Calcium carbonate: "Super 1500" manufactured by Maruo Calcium Co., Ltd. Clay: "Catalpo" manufactured by Sanyo Clay Industries Co., Ltd. Antioxidant ODPA: "Nocrac AD-F" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Stearic acid: "Camellia Stearate" manufactured by NOF Corporation Adhesion improver A: Cytec Industries' "Syrets 964RPC", a mixture of hexamethoxymethylmelamine (65% by mass) and amorphous silica (35% by mass) Adhesion improver B (phenolic resin): "Sumilite Resin PR51732" manufactured by Sumitomo Bakelite Co., Ltd. Co-crosslinking agent MPBM: "Valnoc PM" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Crosslinking accelerator MBTS: "Noccela DM-P" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Sulfur: "MIDAS" manufactured by Bigen Chemical Co., Ltd.

[0137] Core A treated cord (diameter 1.55 mm) made by combining three 1100 dtex PET fiber bundles (360 filaments) and twisting them at a twist factor of 3.0 to form a first twisted yarn, which is then combined with five strands of yarn and twisted at a twist factor of 3.0 to form a ply-twisted cord with a total fineness of 16500 dtex, which has been subjected to an adhesive treatment.

[0138] [Preparation of Sheet-Shaped Rubber Composition] Rubber compositions (compositions for tension rubber layer or compression rubber layer, and adhesive rubber layer) having the formulations shown in Table 1 were kneaded in a Banbury mixer, and the kneaded rubber was passed through a calendar roll to produce uncrosslinked rolled rubber sheets of the specified thickness (sheets for tension rubber layer, compression rubber layer, and adhesive rubber layer).

[0139] [Table 1]

[0140] [Reinforcing fabric] Reinforcement fabric A: Cotton woven fabric (plain weave, consisting of 20-count warp yarns and 20-count weft yarns, warp and weft yarn density 75 threads / 50 mm, basis weight 280 g / m 2 ) Reinforcing fabric B: Woven fabric of blended cotton and PET yarn (mass ratio of cotton to PET: cotton / PET = 35 / 65) (plain weave, composed of 20-count warp yarn and 20-count weft yarn, warp and weft yarn density: 75 threads / 50 mm, basis weight: 280 g / m 2 ).

[0141] Examples 1 to 12 and Comparative Examples 1 to 4 [Preparation of Friction Rubber Composition] A rubber composition having the formulation shown in Table 2 was kneaded in a Banbury mixer to prepare a friction rubber composition (lump uncrosslinked rubber composition).

[0142] [Mooney Scorch Minimum Viscosity (Vm) and Scorch Time] The minimum Mooney scorch viscosity was measured using a friction rubber composition according to the Mooney scorch test of JIS K 6300-1 (2013). An L-shaped rotor was used, and the test temperature was 125°C. A polyester film (Lumirror, manufactured by Toray Industries, Inc.) with a thickness of approximately 0.04 mm was placed between the surface where the test piece (the friction rubber composition) and the die came into contact. The die was preheated for 1 minute after closing, and then the rotor was rotated, and the Mooney viscosity was recorded over time. The recorded Mooney viscosity generally exhibited the behavior shown in Figure 2. The value at which the Mooney viscosity reached its minimum was taken as the minimum Mooney scorch viscosity (Vm). The time (time from the start of the test) until the Mooney viscosity increased by 5 points after reaching its minimum value was recorded as the scorch time (t5).

[0143] [Rubber hardness Hs of cross-linked rubber] The friction rubber composition was passed through a calender roll to prepare an uncrosslinked rolled rubber sheet of a predetermined thickness, and the resulting uncrosslinked rolled rubber sheet was then press-heated at 153°C, 2 MPa, and 20 minutes to produce a crosslinked rubber sheet (100 mm x 100 mm x 2 mm thick). Three crosslinked rubber sheets were stacked to form a laminate, which was used as a sample. The rubber hardness Hs (Type A) of the crosslinked rubber sheet was measured using a Type A durometer in accordance with the spring durometer hardness test specified in JIS K 6253 (2012) (Vulcanized rubber and thermoplastic rubber - Determination of hardness).

[0144] [Soft carbon / hard carbon ratio in friction rubber composition] The primary particle diameter of the carbon black in the crosslinked rubber sheet prepared for the rubber hardness measurement was measured, and the ratio of the number of primary particles of carbon black with a primary particle diameter of 40 nm or more to the number of primary particles of carbon black with a primary particle diameter of less than 40 nm was calculated. The primary particle diameter of the carbon black was measured by taking a measurement sample with a thickness of 100 nm from the crosslinked rubber sheet and using a transmission electron microscope (JEOL Ltd., "JEM-2100") at a magnification of 100,000 times to measure all the primary carbon black particles in the field of view as the diameter of a circle having an area equal to the projected area (area-equivalent circle diameter).

[0145] [Preparation of reinforced fabric precursor by friction] Using a calendar roll with three rolls (top roll, center roll, bottom roll) arranged vertically, the friction rubber composition was passed between the top roll and the center roll to roll out a sheet-like rubber composition. The sheet-like rubber composition was then continuously passed through the center roll and the bottom roll, which rotated at different speeds, simultaneously with the reinforcing fabric, to rub the rubber composition into the fibers of the fabric, thereby obtaining a reinforcing fabric precursor. The rotation speeds were 15 rpm for the top roll, 20 rpm for the center roll, and 10 rpm for the bottom roll, and the clearance between the center roll and the bottom roll was 1 mm. Note that only Example 8 used reinforcing fabric B as the reinforcing fabric, while the other Examples and Comparative Examples used reinforcing fabric A.

[0146] [Peeling force] Two friction-treated reinforcement fabric precursors (rubber-coated fabrics) were stacked with the warp yarns aligned and press-heated at 153°C, 2 MPa, and 20 minutes. After heating, the samples were cut into rectangular shapes measuring 150 mm in length in the warp direction and 25 mm in width in the weft direction to prepare samples for peel force measurement. The two fabrics were separated from one end of the sample's length to create a gripping section, and the peel force (the tensile force required to peel the two fabrics) was measured by pulling both gripping sections using a tensile tester [Shimadzu Corporation, "AGS-J10kN"]. The peel force was measured as a wavy curve, and its average was calculated according to Method E of JIS K 6274 (2018). Ignoring the initial rising curve at the start of the test, the maximum and minimum values ​​were read from all peaks of the wavy curve and then averaged.

[0147] [Workability] In producing the reinforcing fabric precursor by friction, the workability was evaluated according to the following criteria.

[0148] 〇…Friction can be handled smoothly ×: There are areas where the friction rubber composition does not adhere to the fabric, and friction processing cannot be carried out smoothly.

[0149] [cost] The raw material costs of the friction rubber compositions were evaluated as a relative value, with the raw material costs of Comparative Example 1 taken as 100.

[0150] [Friction rubber adhesion amount and adhesion rate] 1m for fabric 2 The mass of the friction rubber composition per unit area is referred to as the friction rubber adhesion amount (g / m 2 ) was calculated based on the following formula, and the mass proportion of the friction rubber composition in the reinforcing fabric precursor was calculated based on the following formula as the friction rubber adhesion rate (mass %).

[0151] Friction rubber adhesion amount (g / m 2 ) = basis weight (g / m) of the reinforcing fabric precursor (rubber-attached fabric) after friction treatment 2 ) - Weight (g / m) of the reinforcing fabric precursor (fabric before rubber is attached) before friction treatment 2 ).

[0152] Friction rubber adhesion rate (mass%) = [friction rubber adhesion amount (g / m 2 ) / Balance of reinforcement fabric precursor (rubber-attached fabric) after friction treatment (g / m 2 )]×100.

[0153] [Making wrapped V-belts] The compression rubber layer sheet, the first adhesive rubber layer sheet, the cord, the second adhesive rubber layer sheet, and the tension layer sheet were laminated and attached in this order to the outer circumferential surface of the cylindrical drum to form a cylindrical uncrosslinked sleeve in which the uncrosslinked rubber layer and the cord were laminated. The obtained uncrosslinked sleeve was cut in the circumferential direction while placed on the outer periphery of the cylindrical drum to form a ring-shaped uncrosslinked rubber belt.

[0154] Next, the uncrosslinked rubber belt was removed from the drum, and both side surfaces of the uncrosslinked rubber belt were cut (skived) at a predetermined angle to form the cross section of the uncrosslinked rubber belt into a V-shaped cross section. The uncrosslinked rubber belt with a V-shaped cross section was subjected to a cover wrapping treatment twice to cover it with the reinforcing fabric precursor, thereby forming an uncrosslinked belt molding in which the periphery of the belt main body was covered twice with the reinforcing fabric precursor.

[0155] The resulting uncrosslinked belt molded body was inserted into the groove of a ring mold. Furthermore, a cylindrical rubber sleeve was fitted onto the outer peripheral surface of the ring mold and the uncrosslinked belt molded body, and they were placed in a vulcanization can and pressurized to 1.2 MPa at a temperature of 160°C to obtain a crosslinked belt. The resulting crosslinked belt was removed from the ring mold to obtain a wrapped V-belt with a belt size of SPB1500 [DIN SPB type, cross-sectional dimensions: width 16.3 mm x thickness 13.0 mm, belt length 1500 mm, average thickness of reinforcing fabric (2 ply) 0.55 mm x 2 = 1.1 mm].

[0156] [Wear test] A wrapped V-belt was run under the following conditions, and the wear rate was calculated from the change in the wrapped V-belt's mass before and after running to evaluate its wear resistance. The wrapped V-belt was hung on a biaxial running test machine consisting of a drive (Dr.) pulley with a diameter of 140 mm and a driven (Dn.) pulley also with a diameter of 140 mm. The belt was run for 10 minutes at an ambient temperature of 25°C with an axial load of 1160 N, a drive pulley rotation speed of 1200 rpm, and a load on the driven pulley of 49.3 N·m. The mass of the belt was measured before and after running to evaluate the mass change rate (wear rate).

[0157] Wear rate (%) = [(belt mass before running - belt mass after running) / belt mass before running] x 100.

[0158] Table 2 shows the evaluation results of Examples 1 to 12 and Comparative Examples 1 to 4.

[0159] [Table 2]

[0160] In Examples 1 to 12, the friction rubber had low viscosity and high rubber hardness Hs, so that both processability and abrasion resistance were achieved. A comparison of Examples 1 to 3 showed that adding an appropriate amount of co-crosslinking agent improved abrasion resistance.

[0161] A comparison of Examples 2, 4, and 12 showed that adding an adhesion improver improved the peel strength and abrasion resistance. Furthermore, a comparison of Examples 4 and 12 showed that Example 12, which used a phenolic resin as the adhesion improver, had slightly inferior peel strength and abrasion resistance compared to Example 4, which used adhesion improver A containing a melamine resin.

[0162] A comparison of Examples 4 to 7 shows that the addition of calcium carbonate can improve the abrasion resistance while suppressing an increase in viscosity, and can also reduce costs.

[0163] Comparing Examples 6 and 8, Example 8, which used a woven fabric of a cotton and PET blended yarn as the reinforcing fabric, had improved abrasion resistance compared to Example 6, which used a cotton woven fabric, although the cost was slightly higher.

[0164] A comparison of Examples 4, 9, and 10 shows that changing the carbon black SRF, which contains a large amount of soft carbon, to the carbon black HAF, which contains a large amount of hard carbon, improved abrasion resistance, but increased costs and Vm. In particular, in Example 9, which used only the carbon black HAF, it was necessary to reduce the amount of carbon black blended in order to suppress the increase in Vm and ensure processability.

[0165] A comparison of Examples 6 and 11 shows that Example 11, which used clay as a non-reinforcing filler, had slightly improved abrasion resistance but increased Vm compared to Example 6, which used calcium carbonate.

[0166] Comparative Example 1 had a low amount of carbon black and a low rubber hardness Hs, resulting in poor abrasion resistance. Comparative Examples 2 to 4 each had a high amount of carbon black, co-crosslinking agent, and calcium carbonate, resulting in high viscosity and poor processability. [Industrial Applicability]

[0167] The friction transmission belt of the present invention is not particularly limited as long as it is a friction transmission belt in which at least a portion of the friction transmission surface is covered with a reinforcing fabric, and can be used, for example, as a flat belt, a V-belt (such as a wrapped V-belt, a raw-edge V-belt, or a raw-edge cog V-belt), or a V-ribbed belt, and is particularly useful as a wrapped V-belt because of its significant effect of improving wear resistance. [Explanation of symbols]

[0168] 1...Wrapped V-belt 2...Stretch layer 3... Core body 4...Compressed layer 5…Outer covering fabric

Claims

1. A friction transmission belt in which at least a portion of a friction transmission surface is covered with a reinforcing fabric, The reinforcing fabric includes a rubber composition containing a rubber component and a fabric, The friction transmission belt is characterized in that the rubber composition has a Mooney scorch minimum viscosity at 125°C of 21 or less when uncrosslinked, and a rubber hardness Hs of 55 or more when crosslinked.

2. 2. The friction transmission belt according to claim 1, wherein the rubber composition contains carbon black, and the proportion of the carbon black is 45 to 55 parts by mass per 100 parts by mass of the rubber component.

3. 3. The friction transmission belt according to claim 1, wherein the rubber composition contains a co-crosslinking agent, and the ratio of the co-crosslinking agent is 0.5 to 2.5 parts by mass per 100 parts by mass of the rubber component.

4. 3. The friction transmission belt according to claim 1, wherein the rubber composition contains an adhesion improver, and the proportion of the adhesion improver is 0.5 to 4 parts by mass per 100 parts by mass of the rubber component.

5. 3. The friction transmission belt according to claim 1, wherein the rubber composition contains a non-reinforcing filler, and the proportion of the non-reinforcing filler is 10 to 45 parts by mass per 100 parts by mass of the rubber component.

6. 3. The friction transmission belt according to claim 1, wherein the rubber composition contains a tackifier, and the proportion of the tackifier is 5 to 30 parts by mass per 100 parts by mass of the rubber component.

7. 3. The friction transmission belt according to claim 1, wherein both surfaces of said reinforcing fabric are friction-treated with said rubber composition.

8. 3. The friction power transmission belt according to claim 1, wherein the ratio of the rubber composition in the reinforcing fabric is 30 to 50% by mass.

9. 3. The friction transmission belt according to claim 1, which is substantially free of metal particles.

10. 3. The friction power transmission belt according to claim 1, wherein the reinforcing fabric forms an outer cover fabric of a wrapped V-belt.

11. 3. The method for producing a friction transmission belt according to claim 1, further comprising a friction step of producing a reinforcing fabric precursor by friction-treating at least one surface of a fabric with a rubber composition containing an uncrosslinked rubber component.

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