CROSS REFERENCE TO RELATED APPLICATIONS

This is a U.S. National Phase Application under 35 U.S.C. § 371 of International Application No. PCT/JP2017/019164, filed May 23, 2017, which claims priority to Japanese Application Nos. 2016-102618 filed May 23, 2016 and 2017-096586 filed May 15, 2017, which was published Under PCT Article 21(2), the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a power transmission belt such as a toothed belt having a power transmission surface (meshing power transmission surface) covered with a fiber material (tooth fabric).

BACKGROUND ART

A fiber-reinforced material formed of rubber and fibers has been used in industrial products such as tires, belts, hoses, and rubber covering fabrics. As rubber commonly used for a power transmission belt among these industrial products, ethylene-α-olefin elastomers such as ethylene-propylene-diene copolymer rubber (EPDM) have been known. Since the ethylene-α-olefin elastomers have no unsaturated bond in a main chain and are nonpolar, they have excellent heat resistance and cold resistance; on the other hand, it is very difficult to adhere them with fibers. For example, a rubber toothed belt containing EPDM as a base material is insufficient in adhesive force between the EPDM and a cover fabric or cord, and particularly when traveling at a high temperature, the rubber and the cover fabric at a tooth root part are repeatedly deformed together with thermal deterioration. Therefore, there has been a problem in that peeling occurs between the5rubber and the cord to cause tooth chipping or peeling occurs at an interface between the cover fabric and the rubber, leading to a significant deterioration in durability of the toothed belt.

Regarding the power transmission belt which rubber component is EPDM, as a method for enhancing adhesive force under a high temperature between rubber and a cord, PTL 1 discloses a power transmission belt containing the cord buried in an adhesion rubber layer along a longitudinal direction of the belt, a compression rubber layer disposed on the power transmission surface side adjacent to the adhesion rubber layer, and a tension rubber layer disposed on the back surface side, in which the adhesion rubber layer is formed of an organic peroxide-crosslinked product of a rubber composition obtained by blending from 20 to 70 parts by mass of silica to 100 parts by mass of rubber component containing an ethylene-α-olefin elastomer. This document discloses that the adhesion rubber layer preferably further contains a resorcinol-formalin resin (resorcinol resin) or a melamine polymer from the viewpoint that the adhesiveness between the cord and the belt main body can be maintained at a high level even at high temperature. In addition, a V-ribbed belt and cogged V-belt are disclosed as the power transmission belt.

As disclosed in this document, in a frictional power transmission belt such as a V-ribbed belt and cogged V belt, rubbers of different compositions are often laminated in the adhesion rubber layer and the compression rubber layer. It is considered that a reason for this is because it is advantageous to incorporate more carbon black in order to enhance mechanical properties of the rubber, such as abrasion resistance and modulus, but on the other hand, the adhesive force tends to be decreased as the amount of carbon black is increased. Therefore, in the frictional power transmission belt, it is common to dispose rubber blended specifically for adhesiveness around the fiber material and to form the belt main body with rubber blended with enhanced mechanical properties. Also in PTL 1, a filler (reinforcing agent) blended in the adhesion rubber layer is only silica, which is considered to be a result of avoiding the addition of carbon black which leads to deterioration in the adhesiveness. Therefore, in the frictional power transmission belt, the mechanical properties of the adhesion rubber layer itself are not sufficient, and there is also a structural defect that the belt structure becomes complicated due to the presence of the adhesion rubber layer.

On the other hand, in the case of a toothed belt, there are few cases of using the adhesion rubber layer, and the rubber of the belt main body comes into direct contact with the cord and cover fabric. Therefore, in addition to the abrasion resistance and high modulus required for power transmission, it is required for the rubber layer of the toothed belt to be compatible with the adhesive force with the cord and cover fabric. Therefore, it is not possible to adopt a composition containing only silica as a filler as disclosed in PTL 1, but a composition containing carbon black and having high adhesive force with fiber members is required for the rubber layer of the toothed belt.

PTL 2 discloses a power transmission belt provided with a rubber portion formed by vulcanizing a rubber composition containing rubber, resorcinol and a melamine compound. It is also disclosed that an organic peroxide vulcanizing agent is preferable as a vulcanizing agent (or a crosslinking agent) to be blended in the rubber composition, and it is also used in Examples. As the rubber, hydrogenated nitrile rubber and EPDM are used in Examples. Furthermore, in Examples, 40 parts by mass of silica, 5 parts by mass of carbon black, 1.7 parts by mass or 3.4 parts by mass of melamine compound are blended with respect to 100 parts by mass of EPDM in the rubber composition containing EPDM.

However, in this toothed belt, an organic peroxide is used as a crosslinking agent. Since the organic peroxide attacks, hardens, and deteriorates the resorcinol resin, which is an adhesion treatment agent for the cover fabric, it is difficult to enhance the adhesive force with the cover fabric. In the toothed belt, due to a stress concentrated on the tooth root part, tearing resistance of the rubber is also important. However, since the crosslinking is progressed with the organic peroxide, the tearing resistance is not sufficient. In addition, probably due to the low ratio of the melamine compound to silica, the adhesive force between the rubber portion and the cord is not sufficient, and probably due to a low ratio of carbon black, the mechanical properties such as the abrasion resistance and modulus are also not sufficient.

CITATION LIST

Patent Literature

[PTL 1] JP-A-2008-261489[PTL 2] JP-A-2013-108564

SUMMARY OF INVENTION

Technical Problem

An object of the present invention is to provide a power transmission belt even having a rubber layer containing an ethylene-α-olefin elastomer and a fiber member in contact with the rubber layer provided, the power transmission belt can suppress peeling between the rubber layer and the fiber member and has high mechanical properties such abrasion resistance and modulus.

Another object of the present invention is to provide a power transmission belt which can improve durability even when being used as a toothed belt at high temperature.

Still another object of the present invention is to provide a power transmission belt which can suppress peeling even with the fiber member formed of any fiber of an inorganic fiber or an organic fiber.

Solution to Problem

As a result of intensive studies to achieve the above objects, the present inventors have found that when a rubber layer of a power transmission belt is formed by combining a rubber component containing an ethylene-α-olefin elastomer, a filler containing silica, a vulcanizing agent containing a sulfur vulcanizing agent, and a curable resin containing an amino resin, even in the case where the rubber layer containing an ethylene-α-olefin elastomer and a fiber member in contact with the rubber layer are provided, peeling between the rubber layer and the fiber member can be suppressed and the mechanical properties such abrasion resistance and modulus can be improved. With this the present invention has been completed.

That is, the power transmission belt of the present invention is a power transmission belt provided with a rubber layer and a fiber member being in contact with the rubber layer, in which the rubber layer is formed of a vulcanizate of a rubber composition containing a rubber component containing an ethylene-α-olefin elastomer, a filler containing silica, a vulcanizing agent containing a sulfur vulcanizing agent, and a curable resin containing an amino resin. The amino resin may contain a melamine resin. The filler may further contain carbon black. The ratio of the amino resin may be from about 10 to 50 parts by mass with respect to 100 parts by mass of silica. The ratio of the silica may be from about 10 to 150 parts by mass with respect to 100 parts by mass of carbon black. The rubber layer may contain from 5 to 30 parts by mass of silica and from 10 to 100 parts by mass of carbon black with respect to 100 parts by mass of the rubber component. The sulfur vulcanizing agent may be sulfur. The curable resin may not contain a resorcinol resin. The vulcanizing agent may not contain an organic peroxide. The power transmission belt of the present invention may be a toothed belt which contains a belt main body including a plurality of tooth portions arranged at predetermined intervals along a belt longitudinal direction and a back portion in which a tension member is buried, and a cover fabric covering the surfaces of the plurality of tooth portions. The belt main body (tooth portion and back portion) may be the rubber layer. The tension member may contain an inorganic fiber.

Advantageous Effects of Invention

In the present invention, a rubber layer of the power transmission belt is formed by combining a rubber component containing an ethylene-α-olefin elastomer, a filler containing silica, a vulcanizing agent containing a sulfur vulcanizing agent, and a curable resin containing an amino resin. Therefore, even in the case where the rubber layer containing an ethylene-α-olefin elastomer and a fiber member in contact with the rubber layer are provided peeling between the rubber layer and the fiber member can be suppressed, and the mechanical properties such abrasion resistance and modulus can be improved. Therefore, even in the case of being used as a toothed belt at high temperature, durability can be improved. Furthermore, in the power transmission belt of the present invention, peeling can be suppressed even with the fiber member formed of any fiber of an inorganic fiber or an organic fiber.

