WO2018155722A1 - Transmission belt - Google Patents

Abstract

According to the present invention, the hardness and modulus of a cured product of a rubber composition for transmission belts, said rubber composition being mainly composed of an ethylene-α-olefin elastomer, are enhanced without deteriorating cold resistance, heat resistance, adhesiveness, flex fatigue resistance and wear resistance. According to the present invention, a transmission belt is formed from a cured product of a rubber composition which contains a rubber component that contains an ethylene-α-olefin elastomer, an α,β-unsaturated carboxylic acid metal salt, magnesium oxide, an organic peroxide and an inorganic filler, and which is adjusted so that the ratio of the magnesium oxide is 2-20 parts by mass relative to 100 parts by mass of the rubber component, while being 5 parts by mass or more relative to 100 parts by mass of the α,β-unsaturated carboxylic acid metal salt. The ratio of the α,β-unsaturated carboxylic acid metal salt may be around 5-40 parts by mass relative to 100 parts by mass of the rubber component. This transmission belt is applicable as a transmission belt that is used for CVT driving, such as a raw edge cogged V-belt.

Description

Transmission belt

The present invention relates to a transmission belt including a cured product of a rubber composition including an ethylene-α-olefin elastomer capable of realizing high hardness and high modulus.

As a power transmission means, friction transmission belts and toothed belts have been used for a long time. For example, V-belts and V-ribbed belts are commonly used for driving automotive engine accessories, toothed belts for driving OHC (overhead camshaft), and low-edge cogged V-belts for driving CVT (continuously variable transmission). Yes. In these applications, in recent years, demands for increased transmission power and a compact layout have become strict, and further development of products that can withstand use under high and low temperature conditions is desired. In particular, the low-edge cogged V-belt used for driving CVTs such as snowmobiles has a wide temperature range from a low temperature to a high temperature because it is exposed to the heat generated by the engine while driving at a low temperature while starting. A rubber composition that can withstand the region is required. In addition, high adhesiveness for suppressing separation between the rubber composition and a fiber member such as a core wire or a reinforcing cloth, and bending fatigue resistance that can be applied to a small-diameter pulley are required for compactness. Further, a high wear resistance that can withstand wear due to contact with the pulley and a high side pressure resistance that can withstand the side pressure from the pulley are also required. In addition, a toothed belt is also required to have a small belt width for compactness, and in order to cope with this, high hardness and high modulus of tooth rubber are required. In order to meet such various demands, the use of ethylene-α-olefin elastomers as elastomers constituting rubber compositions is increasing.

Ethylene-α-olefin elastomers have high heat resistance and weather resistance because they do not have an unsaturated bond in the main chain. Furthermore, since the ethylene-α-olefin elastomer does not have a polar group, it can be highly filled with reinforcing agents such as short fibers and carbon black, and it is relatively easy to achieve high hardness and high modulus. It also has features. However, when an ethylene-α-olefin elastomer is highly filled with a reinforcing agent, it has the following drawbacks. That is, when a large amount of carbon black is added, the heat generated due to the bending of the belt increases, and the durability tends to decrease. Further, when a large amount of short fibers is added, poor dispersion is likely to occur, and cracks are likely to occur. For this reason, various formulations have been studied that increase the hardness and modulus while relatively reducing the amount of reinforcing agent.

For example, in International Publication No. 1996/13544 (Patent Document 1), 100 parts by weight of an ethylene-α-olefin elastomer having an ethylene content of 55 to 78% by weight and a metal salt 1 to 30 of an α, β-unsaturated organic acid are disclosed. A belt (synchronous belt, V-belt, V-ribbed belt) comprising a crosslinked product obtained by crosslinking an elastomer composition containing parts by weight and a reinforcing agent of 0 to 250 parts by weight (preferably 25 to 100 parts by weight) with a free radical donor. It is disclosed. As the reinforcing agent, carbon black, calcium carbonate, talc, clay and hydrous silica are described.

International Publication No. 1997/22662 (Patent Document 2) discloses that α-ethylene-propylene-diene terpolymer (EPDM) having an ethylene content of 50 to 65% by weight and a diene content of less than 10% by weight is α , Β-unsaturated carboxylic acid metal salt 32 to 100 parts by weight and filler 0 to 30 parts by weight, and a power transmission belt (V-ribbed belt, toothed belt) including a peroxide-crosslinked crosslinked product is disclosed. . In this document, as the filler, a white filler such as silicate; aluminum, calcium or magnesium oxide or carbonate is described. In the examples, a composition containing 40 to 60 parts by weight of zinc diacrylate, 10 parts by weight of white filler, 25 parts by weight of carbon black, and 5 parts by weight of dicumyl hydroperoxide is prepared with respect to 100 parts by weight of EPDM.

In WO2010 / 047029 (Patent Document 3), 100 parts by mass of an ethylene-α-olefin elastomer containing 5% by mass to less than 40% by mass of ethylene propylene diene monomer rubber having an ethylene content of 66 to 85% by mass, A power transmission belt comprising a crosslinked product obtained by crosslinking a composition containing 32 to 100 parts by mass of an α, β-unsaturated carboxylic acid metal salt with an organic peroxide is disclosed. In this document, as transmission belts, flat transmission belts, friction transmission belts such as V-belts and V-ribbed belts, and meshing transmission belts such as toothed belts are described. In Examples, based on 100 parts by mass of ethylene-α-olefin elastomer, 32.2 to 100 parts by mass of metal salt of di (meth) acrylic acid, 50 parts by mass of carbon black, 5 parts by mass of zinc oxide, 6 parts by mass of organic peroxide. A composition containing parts has been prepared.

In Patent Documents 1 to 3, the ethylene content of the ethylene-α-olefin elastomer is regulated within a certain range, and the addition amount of the organic acid metal salt is adjusted to obtain a rubber composition having the required performance. Can be estimated. However, these compositions only adjust the balance between the crystallinity due to the ethylene component and the crosslinking with the organic acid metal salt, and even if a belt is formed, cold resistance, heat resistance, adhesiveness, and bending resistance Various requirements required for a transmission belt such as fatigue and wear resistance cannot be satisfied at the same time.

Japanese Patent Application Laid-Open No. 2003-314616 (Patent Document 4) describes 20 to 40 parts by weight of an organic acid metal salt monomer per 100 parts by weight of a rubber component composed of an ethylene-α-olefin elastomer and a hydrogenated nitrile rubber. And a high load transmission belt (cogged V belt, hybrid V belt) comprising a crosslinked product obtained by crosslinking a composition containing 5 to 35 parts by weight of short fibers with peroxide. In the examples, 10 to 50 parts by weight of zinc dimethacrylate, 20 parts by weight of short fibers, 10 parts by weight of zinc oxide, 20 parts by weight of silica, and 7 parts by weight of peroxide are added to 100 parts by weight of EPDM and hydrogenated nitrile rubber. A composition comprising is prepared.

However, in the composition of Patent Document 4, hydrogenated nitrile rubber is blended with ethylene-α-olefin elastomer to improve crack resistance, but the properties of ethylene-α-olefin elastomer such as cold resistance are reduced. The result is a moderate or good performance. Moreover, since it becomes an inhomogeneous composition of the sea-island structure, there is a concern about separation at the time of deterioration over time.

In Japanese Patent Application Laid-Open No. 2002-257199 (Patent Document 5), a composition containing chloroprene rubber as a main rubber and containing a metal oxide, an organic peroxide, and an α, β-unsaturated fatty acid metal salt is disclosed. A power transmission belt (a V-ribbed belt, a V-belt, a cogged V-belt, a flat belt) including a crosslinked product crosslinked with an oxide is disclosed. In this document, zinc oxide, magnesium oxide, and calcium oxide are exemplified as metal oxides, and the function of the metal oxide is described as a function as a cross-linking agent and a function as an acid acceptor (corrosion prevention of mold). ing. In Examples, a V-ribbed belt using a composition containing 5 to 20 parts by mass of aluminum acrylate, 4 parts by mass of magnesium oxide, 5 parts by mass of zinc oxide and an organic peroxide with respect to 100 parts by mass of chloroprene rubber is disclosed. Has been.

However, Patent Document 5 has a problem of improving adhesive wear of a transmission belt containing chloroprene rubber, and does not describe a problem of an ethylene-α-olefin elastomer having a structure and characteristics that are significantly different from those of chloroprene rubber. Furthermore, the cold resistance, heat resistance, and weather resistance of chloroprene rubber are not as good as those of ethylene-α-olefin elastomers, and are insufficient in the recent severe use environment such as low edge cogged V-belts.

That is, according to the above-mentioned patent document, the performance required for the recent transmission belt cannot be sufficiently satisfied. In particular, the hardness and modulus of rubber, the adhesiveness, the bending fatigue resistance required for the belt, and the durability in a wide temperature range (particularly adhesiveness and bending fatigue resistance) are in a trade-off relationship, It was difficult to achieve both.

International Publication No. 1996/13544 (Claims, page 10, lines 21 to 25, FIGS. 1 to 3) International Publication No. 1997/22662 (Claims, page 3, lines 14 to 17, line 3 from the bottom of page 3, line 1 to page 4, line 1) International Publication No. 2010/047029 (Claims, Paragraph [0039], Examples) Japanese Patent Application Laid-Open No. 2003-314616 (Claim 1, FIGS. 1 and 3, Examples) Japanese Patent Laid-Open No. 2002-257199 (Claim 1, paragraph [0022], Example)

The object of the present invention is to improve the hardness and modulus of a cured product of a rubber composition mainly composed of an ethylene-α-olefin elastomer without impairing cold resistance, heat resistance, adhesion, bending fatigue resistance, and wear resistance. An object of the present invention is to provide a transmission belt including a cured product of a rubber composition that can be enhanced.

As a result of intensive studies to achieve the above-mentioned problems, the present inventors have found that an ethylene-α-olefin elastomer, an α, β-unsaturated carboxylic acid metal salt, magnesium oxide, an organic peroxide, and an inorganic filler. In addition, by adjusting the ratio of the magnesium oxide, transmission with ethylene-α-olefin elastomer as the main component without impairing cold resistance, heat resistance, adhesion, bending fatigue resistance, and wear resistance. The present inventors have found that the hardness and modulus of the cured product of the rubber composition for belts can be increased.

That is, the transmission belt of the present invention is a rubber containing a rubber component containing an ethylene-α-olefin elastomer, an α, β-unsaturated carboxylic acid metal salt, magnesium oxide, an organic peroxide, and an inorganic filler. A transmission belt comprising a cured product of the composition, wherein the proportion of the magnesium oxide is 2 to 20 parts by mass with respect to 100 parts by mass of the rubber component, and the α, β-unsaturated carboxylic acid metal salt 100 It is 5 mass parts or more with respect to a mass part. The proportion of the α, β-unsaturated carboxylic acid metal salt may be about 5 to 40 parts by mass with respect to 100 parts by mass of the rubber component. The ratio of the organic peroxide may be about 2 to 6 parts by mass with respect to 100 parts by mass of the rubber component. The proportion of magnesium oxide may be about 5 to 300 parts by mass with respect to 100 parts by mass of the α, β-unsaturated carboxylic acid metal salt. The rubber component may contain 80% by mass or more of an ethylene-α-olefin elastomer. The ethylene-α-olefin elastomer may contain 80% by mass or more of an ethylene-propylene-diene terpolymer. The α, β-unsaturated carboxylic acid metal salt may be at least one selected from zinc methacrylate and zinc acrylate. The inorganic filler may contain carbon black. The proportion of the inorganic filler may be about 40 to 100 parts by mass with respect to 100 parts by mass of the rubber component. The inorganic filler may further contain silica. The mass ratio of the carbon black to the silica may be about the former / the latter = 60/40 to 99/1. The rubber composition may further contain zinc oxide. The cured product of the rubber composition may have a cured product having a rubber hardness (JIS-A) of about 91 to 98 degrees. The rubber composition may further contain short fibers. The proportion of the short fibers may be about 20 to 40 parts by mass with respect to 100 parts by mass of the rubber component. The short fiber may be an aramid short fiber. The rubber composition may include short fibers, and the cured product of the rubber composition may have a bending stress of about 8 to 15 MPa in a direction perpendicular to the orientation direction of the short fibers. The power transmission belt of the present invention may be a low edge cogged V belt used for CVT driving.

In the present specification and claims, the “direction orthogonal to the orientation direction” does not have to be a completely orthogonal direction, and may be a direction in the range of the orthogonal direction ± 5 °.

In the present invention, the ratio of the magnesium oxide is adjusted in a combination of an ethylene-α-olefin elastomer, an α, β-unsaturated carboxylic acid metal salt, magnesium oxide, an organic peroxide, and an inorganic filler. Therefore, the hardness and modulus of the cured product of the rubber composition mainly composed of ethylene-α-olefin elastomer can be increased without impairing cold resistance, heat resistance, adhesion, bending fatigue resistance, and wear resistance. Can do. Therefore, it can be used for a transmission belt such as a low-edge cogged V-belt or a toothed belt, which is required to increase transmission power and to make the layout compact, and particularly to a low-edge cogged V-belt used for CTV driving.

FIG. 1 is a schematic perspective view showing an example of a transmission belt (low edge cogged V belt) of the present invention. FIG. 2 is a schematic cross-sectional view of the transmission belt of FIG. 1 cut in the belt longitudinal direction. FIG. 3 is a schematic diagram for explaining a method of measuring the bending stress of the transmission belt obtained in the example. FIG. 4 is a schematic diagram for explaining a durability running test of the transmission belt obtained in the example. FIG. 5 is a schematic perspective view of a double cogged V-belt manufactured in the example.

[Rubber composition]
The transmission belt of the present invention is a rubber composition containing a rubber component containing an ethylene-α-olefin elastomer, an α, β-unsaturated carboxylic acid metal salt, magnesium oxide, an organic peroxide, and an inorganic filler. It is sufficient if the cured product is included.

(Rubber component)
The rubber component preferably contains an ethylene-α-olefin elastomer from the viewpoint of excellent cold resistance, heat resistance, and weather resistance.

Examples of the ethylene-α-olefin elastomer (ethylene-α-olefin rubber) include ethylene-α-olefin rubber and ethylene-α-olefin-diene rubber.

Examples of the α-olefin constituting the elastomer include linear α-C _3-12 olefins such as propylene, butene, pentene, methylpentene, hexene and octene. These α-olefins can be used alone or in combination of two or more. Of these α-olefins, α-C _3-4 olefins (particularly propylene) such as propylene are preferred.

Examples of the diene monomer constituting the elastomer usually include non-conjugated diene monomers such as dicyclopentadiene, methylene norbornene, ethylidene norbornene, 1,4-hexadiene, and cyclooctadiene. These diene monomers can be used alone or in combination of two or more. Of these diene monomers, ethylidene norbornene and 1,4-hexadiene (particularly ethylidene norbornene) are preferred.

Representative ethylene-α-olefin elastomers include, for example, ethylene-α-olefin rubber [ethylene-propylene rubber (EPM), ethylene-butene rubber (EBM), ethylene-octene rubber (EOM), etc.], ethylene-α-olefin. -Diene rubber [ethylene-propylene-diene terpolymer (EPDM)] and the like. These ethylene-α-olefin elastomers can be used alone or in combination of two or more.

Among these ethylene-α-olefin elastomers, ethylene-α-olefin-dienes such as ethylene-α-C _3-4 olefin-diene terpolymer rubbers are excellent because of their excellent cold resistance, heat resistance, and weather resistance. Ternary copolymer rubber is preferred, and EPDM is particularly preferred. Therefore, the proportion of EPDM may be 50% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more (particularly 95% by mass) with respect to the total ethylene-α-olefin elastomer. It may be mass% (EPDM only).

In the ethylene-α-olefin elastomer, the ratio (mass ratio) of ethylene to α-olefin is the former / the latter = 40/60 to 90/10, preferably 45/55 to 85/15 (for example, 50/50 to 80). / 20), more preferably about 52/48 to 70/30 (particularly 55/45 to 60/40).

When the ethylene-α-olefin elastomer contains a diene monomer, the proportion of the diene monomer can be selected from the range of about 1 to 15% by mass, for example, 1.5 to 12% by mass, preferably 2 to 10%, based on the whole elastomer. It may be about mass% (especially 2.5 to 5 mass%).

The iodine value of the ethylene-α-olefin elastomer containing a diene monomer may be, for example, about 3 to 40, preferably about 5 to 30, and more preferably about 10 to 20. If the iodine value is too small, vulcanization of the rubber composition will be insufficient and wear and adhesion will easily occur. Conversely, if the iodine value is too large, the scorch of the rubber composition will become short and difficult to handle and heat resistance Tend to decrease.

As long as the rubber component does not impair the effects of the present invention, in addition to the ethylene-α-olefin elastomer, other rubber components such as diene rubber [natural rubber, isoprene rubber, butadiene rubber, chloroprene rubber, styrene Butadiene rubber (SBR), vinylpyridine-styrene-butadiene copolymer rubber, acrylonitrile butadiene rubber (nitrile rubber); hydrogenated nitrile rubber (including mixed polymer of hydrogenated nitrile rubber and unsaturated carboxylic acid metal salt), etc. Hydrogenated products of the diene rubbers, etc.], olefin rubbers (polyoctenylene rubber, ethylene-vinyl acetate copolymer rubber, chlorosulfonated polyethylene rubber, alkylated chlorosulfonated polyethylene rubber, etc.), epichlorohydrin rubber, acrylic Rubber, silicone rubber, cormorant Tangomu, may contain a such as fluorine rubber.

The ratio of the ethylene-α-olefin elastomer may be 50% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more (particularly 95% by mass or more), and 100% by mass. It may be mass% (rubber component is ethylene-α-olefin elastomer only). If the proportion of the ethylene-α-olefin elastomer is too small, the cold resistance and heat resistance may be lowered.

(Α, β-unsaturated carboxylic acid metal salt)
The α, β-unsaturated carboxylic acid metal salt may be a compound in which an unsaturated carboxylic acid having one or more carboxyl groups and a metal are ionically bonded. Examples of the unsaturated carboxylic acid include unsaturated monocarboxylic acids such as (meth) acrylic acid and crotonic acid, and unsaturated dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid, and citraconic acid. These unsaturated carboxylic acids can be used alone or in combination of two or more. Of these unsaturated carboxylic acids, unsaturated monocarboxylic acids such as (meth) acrylic acid are preferred.

Examples of the metal include Group 2 metals (magnesium, calcium, etc.), Group 4 metals (titanium, zirconium, etc.), Group 8 metals (iron, etc.), Group 10 metals (nickel, etc.), Examples include Group metals (such as copper), Group 12 metals (such as zinc), Group 13 metals (such as aluminum), and Group 14 metals (such as lead). These metals can be used alone or in combination of two or more. Of these metals, polyvalent metals, for example, divalent metals such as magnesium, calcium and zinc, and trivalent metals such as aluminum (especially divalent metals such as zinc) are preferable.

Among these, bifunctional monocarboxylic acid divalent metal salts having two radical polymerizable groups in one molecule, for example, zinc (meth) acrylate such as zinc methacrylate [zinc di (meth) acrylate or bis (Meth) acrylic acid zinc], magnesium (meth) acrylates such as magnesium methacrylate, and trifunctional monocarboxylic acid trivalent metal salts having three radical polymerizable groups in one molecule, such as (meth) acrylic Preferred are aluminum acrylate [aluminum tri (meth) acrylate], more preferably zinc (meth) acrylate and / or aluminum acrylate, selected from zinc (meth) acrylate (ie, zinc methacrylate and zinc acrylate). At least one) is particularly preferred. Furthermore, a bifunctional monocarboxylic acid divalent metal salt (particularly zinc methacrylate) is preferable from the viewpoint of excellent balance of various properties.

The proportion of the α, β-unsaturated carboxylic acid metal salt is 1 to 50 parts by weight, preferably 5 to 40 parts by weight, more preferably 8 to 35 parts by weight (particularly 10 to 30 parts by weight) based on 100 parts by weight of the rubber component. Part) degree. If the proportion of the α, β-unsaturated carboxylic acid metal salt is too small, the hardness and modulus of the cured product of the rubber composition may be reduced. On the other hand, if the proportion is too large, the adhesion and bending fatigue resistance will be reduced. There is a risk of doing.

(Magnesium oxide)
In the present invention, by combining magnesium oxide at a predetermined ratio with the α, β-unsaturated carboxylic acid metal salt, cold resistance, heat resistance, adhesiveness, and bending fatigue resistance of the cured product of the rubber composition The hardness and modulus can be improved while maintaining the wear resistance.

The proportion of magnesium oxide is 2 to 20 parts by weight, preferably 3 to 18 parts by weight, more preferably 5 to 15 parts by weight (particularly 8 to 13 parts by weight) with respect to 100 parts by weight of the rubber component. May be. The proportion of magnesium oxide is 5 parts by mass or more (eg, 5 to 300 parts by mass) with respect to 100 parts by mass of the α, β-unsaturated carboxylic acid metal salt, for example, 5 to 250 parts by mass (eg, 5 to 200 parts by mass). Part), preferably 10 to 150 parts by weight, more preferably about 15 to 100 parts by weight (particularly 20 to 80 parts by weight). If the proportion of magnesium oxide is too small, the hardness and modulus of the cured product of the rubber composition may be decreased. Conversely, if the proportion is too large, adhesiveness and bending fatigue resistance may be decreased.

(Organic peroxide)
As the organic peroxide, organic peroxides usually used for crosslinking of rubber and resin, for example, diacyl peroxide, peroxy ester, dialkyl peroxide (for example, dicumyl peroxide, t-butyl cumyl peroxide) are used. Oxide, 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 organic peroxides can be used alone or in combination of two or more. Further, the organic peroxide is preferably a peroxide having a decomposition temperature of about 150 to 250 ° C. (for example, 175 to 225 ° C.) for obtaining a half-life of 1 minute by thermal decomposition.

The proportion of the organic peroxide is, for example, about 1 to 10 parts by weight, preferably 2 to 8 parts by weight, more preferably 2 to 6 parts by weight (eg 3 to 6 parts by weight) with respect to 100 parts by weight of the rubber component. It may be.

(Inorganic filler)
In the present invention, by adding an inorganic filler to the combination of the α, β-unsaturated carboxylic acid metal salt and magnesium oxide, the cured product of the rubber composition has cold resistance, heat resistance, adhesion, and bending resistance. Wear resistance, hardness, and modulus can be improved while maintaining fatigue.

Examples of inorganic fillers (inorganic fillers) include carbonaceous materials (carbon black, graphite, etc.), metal compounds or synthetic ceramics [metal oxides such as calcium oxide, barium oxide, iron oxide, copper oxide, titanium oxide, and aluminum oxide. (Metal oxides other than magnesium oxide and zinc oxide), metal silicates such as calcium silicate and aluminum silicate, metal carbides such as silicon carbide and tungsten carbide, metal nitride such as titanium nitride, aluminum nitride and boron nitride , Metal carbonates such as magnesium carbonate and calcium carbonate, metal sulfates such as calcium sulfate and barium sulfate], mineral materials (zeolite, diatomaceous earth, calcined diatomaceous earth, activated clay, alumina, silica, talc, mica, kaolin , Sericite, bentonite, montmorillo Ito, smectite, such as clay), and the like. These inorganic fillers can be used alone or in combination of two or more.

Of these inorganic fillers, carbon black and / or silica are preferable, and it is particularly preferable that at least carbon black is included in the cured product of the rubber composition from the viewpoint of improving the hardness, modulus, and wear resistance.

Examples of carbon black include SAF, ISAF, HAF, FEF, GPF, and HMF. These carbon blacks can be used alone or in combination of two or more. Among these, FEF is preferable because the balance between the reinforcing effect and the dispersibility is good and the heat generated when the belt is bent is small.

The average particle size of carbon black can be selected from the range of, for example, about 5 to 200 nm, and is, for example, about 10 to 150 nm, preferably 15 to 100 nm, and more preferably 20 to 80 nm (particularly 30 to 50 nm). If the average particle size of the carbon black is too small, uniform dispersion may be difficult, and if it is too large, the hardness, modulus, and wear resistance may be reduced.

It is particularly preferable that the inorganic filler containing carbon black is combined with silica from the viewpoint that adhesion can be improved in addition to hardness, modulus and wear resistance.

Silica is a fine bulky white powder formed of silicic acid and / or silicate, and has a plurality of silanol groups on its surface, so it can be chemically bonded to the rubber component.

Silica includes dry silica, wet silica, surface-treated silica, and the like. Silica can also be classified into, for example, dry process white carbon, wet process white carbon, colloidal silica, precipitated silica, and the like according to the classification in the production method. These silicas can be used alone or in combination of two or more. Of these, wet-type white carbon containing hydrous silicic acid as a main component is preferable because it has many surface silanol groups and a strong chemical bonding force with a rubber component.

The average particle diameter of silica is, for example, about 1 to 1000 nm, preferably 3 to 300 nm, more preferably 5 to 100 nm (particularly 10 to 50 nm). If the particle size of the silica is too large, the cured product of the rubber composition may have reduced mechanical properties. If it is too small, it may be difficult to uniformly disperse.

Silica may be non-porous or porous, but the nitrogen adsorption specific surface area by the BET method is, for example, 50 to 400 m ² / g, preferably 70 to 350 m ² / g, more preferably 100. It may be about ˜300 m ² / g (especially 150 to 250 m ² / g). If the specific surface area is too large, it may be difficult to uniformly disperse, and if the specific surface area is too small, the mechanical properties of the rubber layer may be deteriorated.

The proportion of the inorganic filler can be selected from the range of about 10 to 150 parts by mass with respect to 100 parts by mass of the rubber component, for example, 40 to 100 parts by mass, preferably 50 to 80 parts by mass, and more preferably 60 to 70 parts by mass. About a part. If the proportion of the inorganic filler is too small, the hardness, modulus and wear resistance of the cured product of the rubber composition may be reduced, and conversely if too large, the bending fatigue resistance may be reduced.

When the inorganic filler contains carbon black and silica, the mass ratio of carbon black to silica can be selected from the range of the former / the latter = 50/50 to 99.9 / 0.1, for example, 60/40 to 99 / 1, preferably 70/30 to 95/5, more preferably about 80/20 to 90/10. If the proportion of carbon black is too small, the hardness, modulus and wear resistance of the cured product of the rubber composition may be reduced, and conversely if too high, the adhesion may be reduced.

The total ratio of carbon black and silica (in the case of carbon black alone, the ratio of carbon black) may be 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass with respect to the entire inorganic filler. % Or more (especially 80% by mass or more), or 90% by mass or more (particularly 100% by mass).

(Zinc oxide)
The rubber composition may further contain zinc oxide. By combining zinc oxide as the metal oxide in addition to the magnesium oxide, hardness and modulus can be improved and the balance of various properties can be improved in the cured product of the rubber composition.

The proportion of zinc oxide is, for example, about 0.5 to 20 parts by weight, preferably 1 to 15 parts by weight, more preferably 2 to 10 parts by weight (particularly 3 to 8 parts by weight) with respect to 100 parts by weight of the rubber component. It may be. The proportion of zinc oxide is, for example, about 10 to 1000 parts by weight, preferably 20 to 500 parts by weight, more preferably 30 to 200 parts by weight (particularly 50 to 100 parts by weight) with respect to 100 parts by weight of magnesium oxide. Also good. If the proportion of zinc oxide is too small or too large, the balance of various properties may be lowered.

(Short fiber)
The rubber composition may further contain short fibers. Examples of short fibers include polyolefin fibers (polyethylene fibers, polypropylene fibers, etc.), polyamide fibers (polyamide 6 fibers, polyamide 66 fibers, polyamide 46 fibers, aramid fibers, etc.), polyalkylene arylate fibers (polyethylene terephthalate (PET)). Fibers, poly C _2-4 alkylene C _6-14 arylate fibers such as polyethylene naphthalate (PEN) fibers, etc.], vinylon fibers, polyvinyl alcohol fibers, synthetic fibers such as polyparaphenylene benzobisoxazole (PBO) fibers; Natural fibers such as cotton, hemp and wool; inorganic fibers such as carbon fibers are widely used. These short fibers can be used alone or in combination of two or more. Among these short fibers, synthetic fibers and natural fibers, especially synthetic fibers (polyamide fibers, polyalkylene arylate fibers, etc.), among others, are rigid and have high strength and modulus, and are at least easy to protrude from the surface of the compressed rubber layer. Short fibers including aramid fibers are preferred. Aramid short fibers also have high wear resistance. Aramid fibers are commercially available, for example, under the trade names “Conex”, “Nomex”, “Kevlar”, “Technola”, “Twaron”, and the like.

The average fiber diameter of the short fibers is, for example, about 1 to 100 μm, preferably 3 to 50 μm, more preferably about 5 to 30 μm (particularly 10 to 20 μm). If the average fiber diameter is too large, the cured product of the rubber composition may have reduced mechanical properties. If it is too small, it may be difficult to disperse uniformly.

The average length of the short fibers may be, for example, about 1 to 20 mm, preferably about 1.2 to 15 mm (for example, 1.5 to 10 mm), and more preferably about 2 to 5 mm (especially 2.5 to 4 mm). If the average length of the short fibers is too short, when the cured product of the rubber composition is used for the belt, the mechanical properties (for example, the modulus) in the direction of preparation may not be sufficiently improved. In addition, the dispersibility of the short fibers in the rubber composition may be reduced, and the bending fatigue resistance may be reduced.

From the viewpoint of dispersibility and adhesiveness of the short fibers in the rubber composition, at least the short fibers are preferably subjected to an adhesion treatment (or surface treatment). In addition, it is not necessary for all the short fibers to be subjected to the adhesion treatment, and the short fibers subjected to the adhesion treatment and the short fibers not subjected to the adhesion treatment (untreated short fibers) may be mixed or used together.

In the short fiber adhesion treatment, various adhesion treatments, for example, treatment solutions containing an initial condensate of phenols and formalin (such as a prepolymer of a novolak or resol type phenol resin), treatment solutions containing a rubber component (or latex). , Treatment with a treatment liquid containing the initial condensate and a rubber component (latex), a silane coupling agent, an epoxy compound (epoxy resin, etc.), a treatment liquid containing a reactive compound (adhesive compound) such as an isocyanate compound, etc. be able to. In a preferred adhesion treatment, the short fibers are treated with a treatment solution containing the precondensate and a rubber component (latex), particularly at least a resorcin-formalin-latex (RFL) solution. Such treatment liquids may be used in combination. For example, short fibers may be pre-treated with a conventional adhesive component such as an epoxy compound (epoxy resin or the like) or a reactive compound (adhesive compound) such as an isocyanate compound. After processing, you may process with RFL liquid.

The proportion of short fibers is, for example, about 5 to 100 parts by weight, preferably 10 to 50 parts by weight, more preferably 20 to 40 parts by weight (especially 25 to 35 parts by weight) with respect to 100 parts by weight of the rubber component. May be. If the proportion of short fibers is too small, the mechanical properties of the cured product of the rubber composition may be reduced. Conversely, if the proportion is too large, it may be difficult to uniformly disperse and the bending fatigue resistance may be reduced. There are (other additives)
The rubber composition may be prepared by using conventional additives, vulcanization aids, vulcanization accelerators, vulcanization retarders, and softeners (oils such as paraffinic oil, naphthenic oil, and process oil) as necessary. , Processing agents or processing aids (stearic acid, stearic acid metal salts, wax, paraffin, fatty acid amide, etc.), anti-aging agents (antioxidants, thermal anti-aging agents, anti-bending cracking agents, anti-ozone degradation agents, etc.) , Colorants, tackifiers, plasticizers, coupling agents (such as silane coupling agents), stabilizers (such as UV absorbers and heat stabilizers), lubricants, flame retardants, antistatic agents, etc. Good. These additives can be used alone or in combination of two or more.

The total proportion of other additives may be about 1 to 100 parts by weight, preferably about 5 to 50 parts by weight, and more preferably about 10 to 20 parts by weight with respect to 100 parts by weight of the rubber component. For example, with respect to 100 parts by mass of the rubber component, the ratio of the softening agent is 1 to 20 parts by mass (especially 5 to 15 parts by mass), and the ratio of the processing (auxiliary) agent is 0.1 to 5 parts by mass (particularly 0.5). To 3 parts by mass), and the proportion of the antioxidant may be about 0.5 to 20 parts by mass (particularly 1 to 10 parts by mass).

(Characteristics of cured product of rubber composition)
The cured product of the rubber composition has a large rubber hardness and modulus. Specifically, the rubber hardness (JIS-A) of the cured product of the rubber composition is, for example, 90 to 100 degrees, preferably 91 to 98 degrees (eg 93 to 97 degrees), more preferably 95 to 98 degrees (particularly 96). (About 97 degrees). In the present specification and claims, rubber hardness (JIS-A) is measured in accordance with JIS K6253 (2012) for a cured product obtained by press vulcanization at a temperature of 170 ° C. and a pressure of 2.0 MPa for 20 minutes. In detail, it measures by the method as described in the below-mentioned Example.

The cured product of the rubber composition has a bending stress of, for example, 8 to 15 MPa, preferably 10 to 15 MPa, more preferably 12 to 14.5 MPa (particularly 13 to 14.5 MPa) in a direction perpendicular to the orientation direction of the short fibers. It may be a degree. In the present specification and claims, the bending stress is measured by the method described in Examples described later. The “direction orthogonal to the orientation direction” is not limited to a direction orthogonal to the orientation direction, but may be a direction in a range of ± 5 ° in the orthogonal direction. Therefore, the “direction orthogonal to the alignment direction” can also be referred to as a “direction substantially orthogonal to the alignment direction”.

When the rubber composition contains short fibers, the short fibers are usually oriented in a predetermined direction. For example, when the compression rubber layer of the transmission belt is formed with the rubber composition, in order to suppress the compression deformation of the belt against the pressure from the pulley, the short fibers are embedded in the compression rubber layer oriented in the belt width direction. It is preferable.

The rubber composition is used as a cured product vulcanized by a method according to the application. The vulcanization temperature may be, for example, about 120 to 200 ° C. (especially 150 to 180 ° C.).

[Power transmission belt]
Examples of the transmission belt of the present invention include friction transmission belts such as flat belts, V-belts, V-ribbed belts, wrapped V-belts, low-edge V-belts, low-edge cogged V-belts, resin block belts, and meshing transmission belts such as toothed belts. Etc. These power transmission belts only need to contain the rubber composition, but usually the belt body (particularly the compression rubber layer and / or the stretch rubber layer) is formed of a cured product of the rubber composition.

Of these belts, transmission belts such as cogged belts and toothed belts, which are required to increase transmission power and make the layout compact, are preferable, and cogged belts are particularly preferable.

The cogged belt of the present invention includes an adhesive rubber layer in contact with at least a part of a core wire extending in the longitudinal direction of the belt, an extended rubber layer formed on one surface of the adhesive rubber layer, and the other surface of the adhesive rubber layer. A compression rubber layer having a plurality of convex portions (cog portions) formed at predetermined intervals along the longitudinal direction of the belt and frictionally engaging with the pulleys on the side surfaces As long as it has. Such a cogged belt includes a cogged belt in which the cogged portion is formed only on the compressed rubber layer, and a double cogged belt in which a similar cogged portion is formed on the outer peripheral surface of the stretched rubber layer in addition to the compressed rubber layer. The cogged belt is preferably a V-belt whose side surface of the compression rubber layer is in contact with the pulley (in particular, a transmission belt used in a transmission in which the transmission ratio changes steplessly while the belt is running). Examples of the cogged V belt include a low edge cogged V belt in which a cog is formed on the inner peripheral side of the low edge belt, and a low edge double cogged V belt in which cogs are formed on both the inner peripheral side and the outer peripheral side of the low edge belt. Can be mentioned. Of these, the low-edge cogged V-belt used for CTV driving is particularly preferable.

FIG. 1 is a schematic perspective view showing an example of a transmission belt (low edge cogged V belt) of the present invention, and FIG. 2 is a schematic sectional view of the transmission belt of FIG. 1 cut in the longitudinal direction of the belt.

In this example, the low edge cogged V-belt 1 has a plurality of cogs 1a formed at predetermined intervals along the longitudinal direction of the belt (A direction in the figure) on the inner peripheral surface of the belt body. The cross-sectional shape in the longitudinal direction of the cog 1a is substantially semicircular (curved or corrugated), and the cross-sectional shape in the direction (width direction or B direction in the figure) perpendicular to the longitudinal direction. Is trapezoidal. That is, each cog 1a protrudes from the cog bottom 1b in a cross section in the A direction in a substantially semicircular shape in the belt thickness direction. The low-edge cogged V-belt 1 has a laminated structure, and the reinforcing cloth 2, the stretch rubber layer 3, and the adhesive rubber layer 4 from the belt outer peripheral side toward the inner peripheral side (side where the cog portion 1a is formed). The compressed rubber layer 5 and the reinforcing cloth 6 are sequentially laminated. The cross-sectional shape in the belt width direction is a trapezoidal shape in which the belt width decreases from the belt outer peripheral side toward the inner peripheral side. Furthermore, a core body 4a is embedded in the adhesive rubber layer 4, and the cog 1a is formed on the compressed rubber layer 5 by a cog-molding mold.

The height and pitch of the cog are the same as the conventional cogged V belt. In the compressed rubber layer, the height of the cog portion is about 50 to 95% (especially 60 to 80%) with respect to the thickness of the entire compressed rubber layer, and the pitch of the cog portion (between the central portions of adjacent cog portions). The distance) is about 50 to 250% (especially 80 to 200%) with respect to the height of the cog portion. The same applies to the case where a cog portion is formed in the stretched rubber layer.

In this example, the stretch rubber layer 3 and the compression rubber layer 5 are formed of a cured product of the rubber composition of the present invention. As the adhesive rubber layer, the core, and the reinforcing cloth, a conventional adhesive rubber layer, core, and reinforcing cloth can be used. For example, the following adhesive rubber layer, core, and reinforcing cloth may be used.

(Adhesive rubber layer)
The rubber composition for forming the adhesive rubber layer is a rubber component, a vulcanizing agent or a cross-linking agent (such as a sulfur-based vulcanizing agent such as sulfur) in the same manner as the vulcanized rubber composition of the compressed rubber layer and the stretch rubber. Co-crosslinking agent or crosslinking aid (such as maleimide crosslinking agent such as N, N'-m-phenylene dimaleimide), vulcanization accelerator (such as TMTD, DPTT, CBS), inorganic filler (such as carbon black, silica) , Softeners (oils such as paraffinic oils), processing agents or processing aids, anti-aging agents, adhesion improvers [resorcin-formaldehyde cocondensates, amino resins (condensates of nitrogen-containing cyclic compounds and formaldehyde, For example, melamine resins such as hexamethylol melamine, hexaalkoxymethyl melamine (hexamethoxymethyl melamine, hexabutoxymethyl melamine, etc.), methyl Urea resins such as roll urea, benzoguanamine resins such as methylol benzoguanamine resin), co-condensates thereof (such as resorcin-melamine-formaldehyde co-condensate)], colorants, tackifiers, plasticizers, coupling agents, It may contain a stabilizer, a flame retardant, an antistatic agent, and the like. In the adhesion improver, the resorcin-formaldehyde cocondensate and amino resin may be an initial condensate (prepolymer) of a nitrogen-containing cyclic compound such as resorcin and / or melamine and formaldehyde.

In this rubber composition, as the rubber component, the same type or type of rubber as the rubber component of the rubber composition of the compressed rubber layer and the stretched rubber layer is often used. Further, the ratios of the vulcanizing agent or crosslinking agent, co-crosslinking agent or crosslinking aid, vulcanization accelerator, softening agent and anti-aging agent are the same ranges as the rubber composition of the compression rubber layer and the stretch rubber layer, respectively. You can choose from. In the rubber composition of the adhesive rubber layer, the proportion of the inorganic filler is 10 to 100 parts by weight, preferably 20 to 80 parts by weight, more preferably about 30 to 50 parts by weight with respect to 100 parts by weight of the rubber component. There may be. The ratio of the adhesion improver (resorcin-formaldehyde cocondensate, hexamethoxymethylmelamine, etc.) is 0.1 to 20 parts by weight, preferably 1 to 10 parts by weight, more preferably 100 parts by weight of the rubber component. May be about 2 to 8 parts by mass.

(Core)
Although it does not specifically limit as a core, Usually, the core wire (twisted cord) arranged at predetermined intervals in the belt width direction can be used. The cores are arranged to extend in the longitudinal direction of the belt, and are usually arranged to extend in parallel at a predetermined pitch in parallel with the longitudinal direction of the belt. The core wire only needs to be at least partially in contact with the adhesive rubber layer. The adhesive rubber layer embeds the core wire, the core wire embeds between the adhesive rubber layer and the stretch rubber layer, and the adhesive rubber. Any form of embedding a core wire between the layer and the compressed rubber layer may be employed. Among these, the form in which the adhesive rubber layer embeds the core wire is preferable from the viewpoint that durability can be improved.

Examples of the fibers constituting the core wire include the same fibers as the short fibers. Among these fibers, from the viewpoint of high modulus, synthesis of polyester fibers (polyalkylene arylate fibers) mainly composed of C _2-4 alkylene arylates such as ethylene terephthalate and ethylene-2,6-naphthalate, aramid fibers, etc. Inorganic fibers such as fibers and carbon fibers are widely used, and polyester fibers (polyethylene terephthalate fibers, polyethylene naphthalate fibers) and polyamide fibers are preferable. The fiber may be a multifilament yarn. The fineness of the multifilament yarn may be, for example, about 2200 to 13500 dtex (particularly 6600 to 11000 dtex). The multifilament yarn may contain, for example, 100 to 5,000, preferably 500 to 4,000, more preferably about 1,000 to 3,000 monofilament yarns.

As the core wire, usually a twisted cord using multifilament yarn (for example, various twists, single twists, rung twists, etc.) can be used. The average wire diameter (fiber diameter of the twisted cord) of the core wire may be, for example, 0.5 to 3 mm, preferably 0.6 to 2 mm, more preferably about 0.7 to 1.5 mm. Good.

The core wire may be subjected to adhesion treatment (or surface treatment) in the same manner as the short fibers of the compression rubber layer and the stretch rubber layer in order to improve the adhesion with the rubber component. Similarly to the short fiber, the core wire is preferably subjected to adhesion treatment with at least the RFL solution.

(Reinforcing cloth)
When a reinforcing cloth is used in the friction transmission belt, the reinforcing cloth is not limited to a form in which the reinforcing cloth is laminated on the surface of the compressed rubber layer. For example, the reinforcing cloth is applied to the surface of the stretched rubber layer (the surface opposite to the adhesive rubber layer). It may be laminated, or may be a form in which a reinforcing layer is embedded in a compressed rubber layer and / or a stretched rubber layer (for example, a form described in Japanese Patent Application Laid-Open No. 2010-230146). The reinforcing cloth can be formed of, for example, a cloth material (preferably a woven cloth) such as a woven cloth, a wide angle sail cloth, a knitted cloth, and a non-woven cloth. If necessary, the above-described adhesion treatment, for example, treatment with an RFL solution (immersion treatment) Or the like, or after the adhesive rubber and the cloth material are laminated, they may be laminated on the surface of the compression rubber layer and / or the stretch rubber layer.

[Production method of transmission belt]
The method for producing the transmission belt of the present invention is not particularly limited, and a conventional method can be used. In the case of a low-edge cogged V-belt, for example, a laminated body composed of a reinforcing cloth (lower cloth) and a sheet for a compressed rubber layer (unvulcanized rubber sheet), and teeth and grooves are alternately arranged with the reinforcing cloth facing down. Installed on a flat cogged mold and cogged with a cog pad by press-pressing at a temperature of 60-100 ° C (especially 70-80 ° C) (not fully vulcanized, semi-vulcanized) After producing the pad in the state, both ends of the cog pad may be cut vertically from the top of the cog crest. Furthermore, an inner mother mold (mold formed of vulcanized rubber) in which teeth and grooves are alternately arranged is placed on a cylindrical mold, and a cog pad is wound around the teeth and grooves so that a cog pad is wound. After the first adhesive rubber layer sheet (lower adhesive rubber: unvulcanized rubber sheet) is laminated on this wound cog pad, the core wire (twisting cord) that forms the core body is joined Spinning in a spiral shape, a second adhesive rubber layer sheet (upper adhesive rubber: the same as the adhesive rubber layer sheet), a stretch rubber layer sheet (unvulcanized rubber sheet), a reinforcing cloth (upper cloth) ) May be sequentially wound to produce a molded body. Then, a jacket (jacket made of vulcanized rubber) is put on and the mold is placed in a vulcanizing can, and vulcanized at a temperature of about 120 to 200 ° C (especially 150 to 180 ° C) to prepare a belt sleeve. After passing through the sulfur process, a cutting process may be performed using a cutter or the like to form a compressed rubber layer by cutting so as to form a V-shaped cross section.

In the stretched rubber layer sheet and the compressed rubber layer sheet, as a method of aligning the orientation direction of the short fibers in the belt width direction, a conventional method, for example, rubber between a pair of calendar rolls provided with a predetermined gap is used. Rolled into a sheet shape, cut both sides of the rolled sheet with short fibers oriented in the rolling direction in a direction parallel to the rolling direction, and rolled the rolled sheet to have a belt forming width (length in the belt width direction) Examples include a method in which side surfaces cut in a direction perpendicular to the direction and in a direction parallel to the rolling direction are joined together. For example, a method described in Japanese Patent Laid-Open No. 2003-14054 can be used. In this method, the unvulcanized sheet in which short fibers are oriented by such a method is placed and vulcanized so that the orientation direction of the short fibers is the width direction of the belt.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. In the following examples, the raw materials used in the examples and the measurement methods or evaluation methods for each physical property are shown below. Unless otherwise specified, “part” and “%” are based on mass.

[material]
EPDM1: "EP93" manufactured by JSR Corporation, ethylene content 55 wt%, diene content 2.7 wt%
EPDM2: “EP24” manufactured by JSR Corporation, ethylene content 54% by weight, diene content 4.5% by weight
Para-type aramid short fiber: Teijin Co., Ltd., Twaron cut yarn Meta-type aramid short fiber: Teijin Ltd., Cornex cut yarn Carbon black: “Cabot Japan Co., Ltd.” “N550”
Silica: “Ultrasil VN3” manufactured by Evonik Degussa Japan, BET specific surface area of 175 m ² / g
Paraffin oil: “Diana Process Oil PW90” manufactured by Idemitsu Kosan Co., Ltd.
Anti-aging agent A: “NOCRACK CD” manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Anti-aging agent B: “NOCRACK MB” manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Anti-aging agent C: “Nonflex OD3” manufactured by Seiko Chemical Co., Ltd.
Zinc oxide: “Zinc oxide 2 types” manufactured by Sakai Chemical Industry Co., Ltd.
Magnesium oxide: “Kyowa Mug 150” manufactured by Kyowa Chemical Industry Co., Ltd.
Stearic acid: Tsubaki stearic acid manufactured by NOF Corporation
Zinc methacrylate: Sanshin Chemical Industry Co., Ltd., “Sunester SK-30”
Bismaleimide: Ouchi Shinsei Chemical Co., Ltd., “Barnock PM”
Organic peroxide: NOF "P-40MB (K)"
Titanium oxide: DuPont "R960"
Resorcinol resin: “Penacolite Resin (B-18-S)” manufactured by INDSPEC Chemical Corporation
Hexamethoxymethylolmelamine: “PP-1890S” manufactured by Power Plast
Vulcanization accelerator A: “Noxeller TT” manufactured by Ouchi Shinsei Chemical Co., Ltd.
Vulcanization accelerator B: “Noxeller CZ” manufactured by Ouchi Shinsei Chemical Co., Ltd.
Vulcanization accelerator C: “Noxeller DM” manufactured by Ouchi Shinsei Chemical Co., Ltd.
Sulfur: Made by Bigen Chemical Co., Ltd. Core wire: Total fineness of two aramid fiber bundles with a fineness of 1,680 dtex, twisted together and twisted together, and twisted in the opposite direction to the twist 10,080 dtex plied cords Reinforcement fabric: Nylon canvas with a 2/2 twill weave (thickness 0.50 mm).

[Physical properties of vulcanized rubber composition]
(1) Hardness An unvulcanized rubber sheet obtained using the rubber composition shown in Table 1 was subjected to press vulcanization (pressure 2.0 MPa) at a temperature of 170 ° C. for 20 minutes to obtain a vulcanized rubber sheet ( 100 mm in length, 100 mm in width, and 2 mm in thickness). In accordance with JIS K6253 (2012), three vulcanized rubber sheets with a thickness of 2 mm were superposed to form a sample with a thickness of 6 mm, and the hardness was measured using a durometer A type hardness tester.

(2) Bending stress The rubber composition shown in Table 1 was press vulcanized at a temperature of 170 ° C. for 20 minutes to prepare a vulcanized rubber molded body (60 mm × 25 mm × 6.5 mm thickness). The short fibers were oriented parallel to the longitudinal direction of the vulcanized rubber molding. As shown in FIG. 3, this vulcanized rubber molded body 21 is placed on and supported on a pair of rolls (diameter 6 mm) 22a and 22b that can be rotated with an interval of 20 mm, and is centered on the upper surface of the vulcanized rubber molded body. The metal pressing member 23 was placed in the width direction (direction perpendicular to the orientation direction of the short fibers) in the portion. The front end portion of the pressing member 23 has a semicircular shape with a diameter of 10 mm, and the vulcanized rubber molded body 21 can be smoothly pressed by the front end portion. Further, at the time of pressing, a frictional force acts between the lower surface of the vulcanized rubber molded body 21 and the rolls 22a and 22b along with the compression deformation of the vulcanized rubber molded body 21, but the rolls 22a and 22b can be rotated. This reduces the influence of friction. A state where the tip of the pressing member 23 is in contact with the upper surface of the vulcanized rubber molded body 21 and is not pressed is set as an initial position. From this state, the vulcanized rubber molded body is moved downward at a speed of 100 mm / min. The upper surface of 21 was pressed, and the stress when the bending strain was 8% was measured as the bending stress. By measuring the bending stress in the direction perpendicular to the orientation direction of the short fibers, it can be judged that if the bending stress is high, the resistance to buckling deformation called dishing during belt running is high, and high load transmission and high durability It can be an index of sex. The measurement temperature was 120 ° C. assuming the belt temperature during running.

[Durability test]
As shown in FIG. 4, the endurance running test was performed using a two-axis running tester including a driving (Dr.) pulley 32 having a diameter of 110 mm and a driven (Dn.) Pulley 33 having a diameter of 240 mm. A low-edge cogged V-belt 31 was hung on each pulley, a drive pulley rotation speed of 6000 rpm and a load of 25 kW was applied, and the belt was run at an ambient temperature of 80 ° C. for 70 hours. The side of the belt after running (the surface in contact with the pulley) was visually observed, and the presence or absence of delamination between the compressed rubber layer and the core wire was examined and the presence or absence of cracks in the lower cog valley was evaluated.

○: No peeling or cracking occurred (high durability, no problem in practical use)
X: Peeling or cracking occurs (durability is low and has practical problems).

The overall judgment was evaluated according to the following criteria.

A: No peeling or cracking occurred in the durability running test and the rubber hardness was 96 degrees or more. ○: No peeling or cracking occurred in the durability running test and the rubber hardness was less than 96 degrees. A crack occurred.

Examples 1 to 9 and Comparative Examples 1 to 7
[Properties of rubber composition of compressed rubber layer and stretched rubber layer]
(Formation of rubber layer)
The rubber compositions in Table 1 (compressed rubber layer, stretched rubber layer) and Table 2 (adhesive rubber layer) were each kneaded using a known method such as a Banbury mixer, and the kneaded rubber was passed through a calender roll. Rolled rubber sheets (compressed rubber layer sheet, stretch rubber layer sheet, adhesive rubber layer sheet) were prepared. The rubber hardness and bending stress were measured for the compressed rubber layer sheet. Table 3 shows the measurement results. Furthermore, the following belts were manufactured using these sheets.

[Manufacture of belts]
A sheet-like cog pad in which the cog portion is molded by molding a laminated body in which a sheet for a compressed rubber layer and a reinforcing cloth with a predetermined thickness is laminated in advance on the surface of a cog-shaped vulcanized rubber inner mold attached to the mold. After being wound and jointed, a lower adhesive rubber sheet, a core wire, an upper adhesive rubber sheet, and a flat stretched rubber layer were sequentially wound to prepare a molded body. Subsequently, the outer surface of the molded body is covered with a cog-shaped outer rubber mold and jacket, and the mold is placed in a vulcanizing can. The temperature is 170 ° C., time 40 minutes, and vulcanized at 0.9 MPa. To obtain a belt sleeve. As vulcanization conditions, conditions similar to vulcanization of unvulcanized adhesive rubber layer sheets, compressed rubber layer sheets and stretched rubber layer sheets were selected. This sleeve was cut into a V shape by a cutter to finish a transmission belt. That is, a double cogged V belt having the structure shown in FIG. 5 was produced. Specifically, in the low-edge cogged V belt in which the compression rubber layer 13 and the stretch rubber layer 14 are formed on both surfaces of the adhesive rubber layer 11 in which the core wire 12 is embedded, respectively, the compression rubber layer 13 and the stretch rubber layer 14 In addition, a belt (size: upper width 35 mm, thickness 15 mm, outer peripheral length 1100 mm) in which the cog portions 16 and 17 are respectively formed was produced. Table 3 shows the evaluation results of the obtained belt running test.

 

As is apparent from Table 3, in Examples 1 to 9, in which the ratio of magnesium oxide is 2 to 20 parts by mass, and the ratio of magnesium oxide to 100 parts by mass of zinc methacrylate is 5 parts by mass or more, the comprehensive judgment is ◎ And it became (circle) and was a favorable result.

In Comparative Example 1 (corresponding to Patent Document 3) not containing magnesium oxide and Comparative Example 2 containing only 1 part by mass of magnesium oxide with respect to 100 parts by mass of the rubber component, the rubber hardness is as low as 90 degrees. Peeling occurred. When the proportion of magnesium oxide is small, the rubber hardness does not increase, and stress is concentrated on the adhesion interface due to buckling deformation, which is considered to cause peeling. Further, Comparative Example 6 and Comparative Example 7 are examples in which the amount of zinc oxide was increased and titanium oxide was added in Comparative Example 1. In these examples, the hardness and bending stress were low as in Comparative Example 1, and peeling occurred in the durability running test. From these results, it can be seen that magnesium oxide is not effective in increasing the amount of zinc oxide or adding titanium oxide in place of magnesium oxide, and in order to maintain durability and improve hardness and bending stress, It turns out to be important. On the other hand, Comparative Example 5 is an example in which zinc methacrylate was not included and bismaleimide was blended as a co-crosslinking agent, but in this case also, the rubber hardness was low and peeling occurred. Thus, for the problem of the present invention, it is not possible to select anything from general-purpose metal oxides and co-crosslinking agents, and the combination of magnesium oxide and α, β-unsaturated carboxylic acid metal salt is particularly effective. I understand that there is.

Comparative Example 3 is an example containing a large amount of magnesium oxide, and Comparative Example 4 is an example containing a large amount of zinc methacrylate. In both examples, although the rubber hardness and bending stress increased greatly, cracks occurred in the durability running test. This is presumably because the dispersion was poor due to too much magnesium oxide, or the rubber composition became stiff due to too much zinc methacrylate and the bending fatigue resistance decreased. It can be seen that magnesium oxide and the α, β-unsaturated carboxylic acid metal salt need to be blended in a well-balanced manner.

On the other hand, in Examples 1 to 9 containing both magnesium oxide and zinc methacrylate and appropriately adjusting the amounts, the rubber hardness and bending stress increased, and no cracks or peeling occurred in the durability running test. The nature was high.

Examples 1 and 2 are examples in which the types of short fibers were changed, but the configuration of the present invention was equally effective for both para-aramid short fibers and meta-aramid short fibers. .

Example 3 is an example in which the amount of magnesium oxide is increased with respect to Example 1, but the hardness and bending stress are increased, and it can be seen that the effect is enhanced.

Example 4 is an example in which the amount of zinc methacrylate is increased with respect to Example 3, and Example 7 is an example in which the amount of zinc methacrylate is increased with respect to Example 1. The hardness and bending stress are remarkably high, and the effect is particularly high.

Similarly, Example 5 is an example in which the amount of magnesium oxide was increased with respect to Example 3. However, the hardness and bending stress were also significantly increased, and particularly good results were obtained.

Example 6 is an example in which a large amount of magnesium oxide was blended and the mass ratio of magnesium oxide to zinc methacrylate was 2.86, but the increase in hardness and bending stress was small. However, in the durability running test, peeling and cracking did not occur, and the performance had no problem in practical use.

Example 8 is an example in which a part of carbon black was replaced with silica as an inorganic filler from the formulation of Example 3, but the hardness and bending stress were slightly increased, and particularly good results were obtained. Silica also has a function of improving the adhesiveness, and it is expected that the resistance to peeling will increase even when running for a longer time.

Example 9 is an example in which the amount of organic peroxide was reduced from the formulation of Example 4, but compared with Example 4, hardness and bending stress were slightly reduced. However, even when the amount of the organic peroxide (crosslinking agent) is small, the hardness and bending stress are high, and even in the durability running test, peeling or cracking does not occur, and the performance has no practical problem.

The transmission belt of the present invention has various transmission belts (flat belt, V-belt, V-ribbed belt, wrapped V-belt, low-edge V-belt) that are required to have cold resistance, heat resistance, adhesion, bending fatigue resistance, wear resistance, and the like. Friction power transmission belts such as low edge cogged V belts and resin block belts; meshing power transmission belts such as toothed belts). In particular, since the transmission belt of the present invention has high hardness and modulus, it can be preferably used as a transmission belt such as a cogged belt or a toothed belt, which is required to increase transmission power and to make the layout compact. As a low-edge cogged V-belt used as

Although the invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit and scope of the invention.
This application is based on Japanese Patent Application No. 2017-035198 filed on Feb. 27, 2017 and Japanese Patent Application No. 2018-012694 filed on Jan. 29, 2018, the contents of which are incorporated herein by reference.

DESCRIPTION OF SYMBOLS 1 ... Power transmission belt 2, 6 ... Reinforcement cloth 3 ... Stretch rubber layer 4 ... Adhesive rubber layer 4a ... Core body 5 ... Compression rubber layer

Claims (14)

1. Transmission belt comprising a cured product of a rubber composition comprising an ethylene-α-olefin elastomer-containing rubber component, an α, β-unsaturated carboxylic acid metal salt, magnesium oxide, an organic peroxide, and an inorganic filler The ratio of magnesium oxide is 2 to 20 parts by mass with respect to 100 parts by mass of the rubber component, and 5 parts by mass or more with respect to 100 parts by mass of the α, β-unsaturated carboxylic acid metal salt. Is a transmission belt.
2. The transmission belt according to claim 1, wherein the ratio of the α, β-unsaturated carboxylic acid metal salt is 5 to 40 parts by mass with respect to 100 parts by mass of the rubber component.
3. The transmission belt according to claim 1 or 2, wherein the ratio of the organic peroxide is 2 to 6 parts by mass with respect to 100 parts by mass of the rubber component.
4. The transmission belt according to any one of claims 1 to 3, wherein the proportion of magnesium oxide is 5 to 300 parts by mass with respect to 100 parts by mass of the α, β-unsaturated carboxylic acid metal salt.
5. The rubber component contains 80% by mass or more of an ethylene-α-olefin elastomer, and the ethylene-α-olefin elastomer contains 80% by mass or more of an ethylene-propylene-diene terpolymer. The power transmission belt according to any one of the above.
6. The transmission belt according to any one of claims 1 to 5, wherein the α, β-unsaturated carboxylic acid metal salt is at least one selected from zinc methacrylate and zinc acrylate.
7. The transmission belt according to any one of claims 1 to 6, wherein the inorganic filler contains carbon black, and the proportion of the inorganic filler is 40 to 100 parts by mass with respect to 100 parts by mass of the rubber component.
8. The transmission belt according to claim 7, wherein the inorganic filler further contains silica, and the mass ratio of carbon black to the silica is the former / the latter = 60/40 to 99/1.
9. The transmission belt according to any one of claims 1 to 8, wherein the rubber composition further contains zinc oxide.
10. The power transmission belt according to any one of claims 1 to 9, wherein the cured product of the rubber composition has a rubber hardness (JIS-A) of 91 to 98 degrees.
11. The transmission belt according to any one of claims 1 to 10, wherein the rubber composition further comprises short fibers, and the proportion of the short fibers is 20 to 40 parts by mass with respect to 100 parts by mass of the rubber component.
12. The power transmission belt according to claim 11, wherein the short fibers are aramid short fibers.
13. The transmission belt according to any one of claims 1 to 12, wherein the rubber composition includes short fibers, and the cured product of the rubber composition has a bending stress of 8 to 15 MPa in a direction perpendicular to the orientation direction of the short fibers. .
14. The power transmission belt according to any one of claims 1 to 13, which is a low edge cogged V belt used for CVT driving.
    

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