阅读说明：本技术 橡胶增强用线和使用其的橡胶制品 (Rubber reinforcing cord and rubber product using same ) 是由 片桐真也 于 2018-06-08 设计创作，主要内容包括：本发明的橡胶增强用线(12)具备至少1条股线。股线包含至少1条丝束和按照覆盖上述丝束的至少一部分表面的方式设置的覆膜。覆膜包含橡胶成分、异氰酸酯化合物、双马来酰亚胺系化合物、炭黑和橡胶改性环氧树脂,所述橡胶成分包含选自羧基改性丁腈橡胶和羧基改性氢化丁腈橡胶中的至少任一者。在覆膜中,相对于橡胶成分100质量份,异氰酸酯化合物为10～50质量份、双马来酰亚胺系化合物为5～25质量份、炭黑为2～18质量份、橡胶改性环氧树脂为5～30质量％。(The rubber reinforcing cord (12) of the present invention comprises at least 1 strand. The strand comprises at least 1 tow and a coating film provided so as to cover at least a part of the surface of the tow. The coating film comprises a rubber component, an isocyanate compound, a bismaleimide compound, carbon black and a rubber-modified epoxy resin, wherein the rubber component comprises at least one selected from carboxyl-modified nitrile rubber and carboxyl-modified hydrogenated nitrile rubber. In the coating film, the amount of the isocyanate compound is 10 to 50 parts by mass, the amount of the bismaleimide compound is 5 to 25 parts by mass, the amount of the carbon black is 2 to 18 parts by mass, and the amount of the rubber-modified epoxy resin is 5 to 30 parts by mass, based on 100 parts by mass of the rubber component.)

1. A rubber-reinforcing cord for reinforcing a rubber product,

the rubber reinforcing cord comprises at least 1 strand,

the strand comprises at least 1 tow and a coating disposed in a manner to cover at least a portion of a surface of the tow,

the coating film comprises a rubber component, an isocyanate compound, a bismaleimide compound, carbon black and a rubber-modified epoxy resin, wherein the rubber component comprises at least one selected from carboxyl-modified nitrile rubber and carboxyl-modified hydrogenated nitrile rubber,

in the coating, the isocyanate compound is 10 to 50 parts by mass, the bismaleimide compound is 5 to 25 parts by mass, the carbon black is 2 to 18 parts by mass, and the rubber-modified epoxy resin is 5 to 30% by mass, based on 100 parts by mass of the rubber component.

2. The rubber-reinforcing cord according to claim 1, wherein the rubber-modified epoxy resin is a nitrile rubber-modified epoxy resin.

3. The rubber-reinforcing cord according to claim 1 or 2, wherein no other coating film is contained other than the coating film.

4. The rubber-reinforcing cord as claimed in any one of claims 1 to 3, wherein the total amount of said isocyanate compound, said bismaleimide compound, said carbon black and said rubber-modified epoxy resin is 100 parts by mass or less with respect to 100 parts by mass of said rubber component.

5. The rubber-reinforcing cord according to any one of claims 1 to 4, wherein the coating film does not contain a resorcinol-formaldehyde condensate.

6. A rubber product reinforced with the rubber reinforcing cord according to any one of claims 1 to 5.

7. The rubber product according to claim 6, which is a rubber tape comprising a matrix rubber and the rubber-reinforcing thread embedded in the matrix rubber.

8. The rubber article of claim 7 wherein said matrix rubber comprises hydrogenated nitrile rubber.

Technical Field

The present invention relates to a rubber reinforcing cord (cord) and a rubber product using the same.

Background

Rubber belts and metal chains are used for driving camshafts of internal combustion engines for automobiles, driving auxiliary machines such as injection pumps, and transmitting power to industrial machines. In recent years, attention has been increasingly paid to energy saving, and from the viewpoint of improvement in fuel consumption and the like, use of a rubber belt having excellent power transmission efficiency has been attracting attention. Further, the rubber belt has advantages of high strength and elastic modulus and being usable even under high load conditions, compared with a metal chain. However, the rubber belt may be reduced in strength when repeatedly subjected to stress, and the use thereof is limited.

Generally, a rubber product such as a rubber belt includes a matrix rubber and a rubber reinforcing cord embedded in the matrix rubber. The strength of the rubber belt depends on the strength of the rubber reinforcing cord. Therefore, the rubber reinforcing cord is an important member for determining the life of the rubber belt.

The rubber reinforcing cord is generally formed of a reinforcing fiber (a yarn bundle including a plurality of filaments) and a coating film for protecting the surface of the reinforcing fiber. This coating film can also improve the adhesion between the rubber-reinforcing cord and the matrix rubber when the rubber-reinforcing cord is embedded in the matrix rubber of the rubber product.

Conventionally, when the matrix rubber is hydrogenated nitrile rubber, a rubber reinforcing cord using a primary coating layer as a base coating layer and a secondary coating layer as a top coating layer contacting the matrix rubber as a rubber product, in which a coating containing chlorosulfonated polyethylene is used as the secondary coating layer, has been known (for example, patent document 1).

Disclosure of Invention

Problems to be solved by the invention

However, the conventional rubber reinforcing cord and rubber product described above have the following problems.

In rubber products, mainly toothed belts for automobiles, hydrogenated nitrile rubber is mainly used as a base rubber. For example, in a conventional first coating film itself formed of a mixed solution (RFL) of a resorcinol-formaldehyde condensate and a rubber latex, adhesion to hydrogenated nitrile rubber is insufficient for a rubber reinforcing cord applied to a rubber product using such a matrix rubber. Therefore, the rubber reinforcing cord needs to have a second coating film mainly composed of chlorosulfonated polyethylene, that is, two or more coating films. In addition, in the case where a large amount of a crosslinking agent is added to impart high adhesiveness to the conventional first coating, there is a case where the first coating itself can obtain adhesion to hydrogenated nitrile rubber as a matrix rubber, but since the crosslinking component is large, there is a new problem that the coating becomes hard and the bending fatigue resistance is lowered.

On the other hand, when the material used for the conventional second coating is used for the first coating, a rubber product reinforced with the rubber reinforcing cord has a problem of poor bendability. This is because: since a film made of chlorosulfonated polyethylene as a main material has high hardness and is hard, the problem of adhesion is solved, but the resistance to repeated bending is weak.

Accordingly, an object of the present invention is to provide a rubber reinforcing cord which has good adhesion to a matrix rubber of a rubber product, particularly a matrix rubber containing hydrogenated nitrile rubber, and can realize higher bending performance without providing a plurality of coating films. Further, another object of the present invention is to provide a rubber product having high bending properties by being reinforced with such a rubber reinforcing cord.

Means for solving the problems

The present invention is a rubber-reinforcing cord for reinforcing a rubber product,

the rubber reinforcing cord comprises at least 1 strand,

the strand comprises at least 1 tow and a coating film provided so as to cover at least a part of the surface of the tow,

the coating film comprises a rubber component, an isocyanate compound, a bismaleimide compound, carbon black and a rubber-modified epoxy resin, wherein the rubber component comprises at least one selected from carboxyl-modified nitrile rubber and carboxyl-modified hydrogenated nitrile rubber,

in the coating film, the isocyanate compound is 10 to 50 parts by mass, the bismaleimide compound is 5 to 25 parts by mass, the carbon black is 2 to 18 parts by mass, and the rubber-modified epoxy resin is 5 to 30 parts by mass, based on 100 parts by mass of the rubber component.

The present invention also provides a rubber product reinforced with the rubber reinforcing cord of the present invention.

Effects of the invention

According to the rubber-reinforcing cord of the present invention, even if a plurality of coatings are not provided, the cord has good adhesion to a matrix rubber of a rubber product, particularly a matrix rubber containing hydrogenated nitrile rubber, and can achieve higher bending performance. Further, the rubber product of the present invention is reinforced with such a rubber reinforcing cord and therefore has high bending properties.

Drawings

Fig. 1 is a partially exploded perspective view schematically showing an example of a rubber product of the present invention.

Fig. 2 is a sectional view showing a strand of the embodiment.

FIG. 3 is a sectional view showing a rubber reinforcing cord of an example.

Fig. 4 is a diagram schematically showing a bending test method performed on the rubber reinforcing cord of the examples and comparative examples.

Detailed Description

Hereinafter, embodiments of the present invention will be specifically described.

[ rubber reinforcing cord ]

The rubber-reinforcing cord of the present embodiment is a cord for reinforcing a rubber product. The rubber reinforcing cord comprises at least 1 strand. The strand comprises at least 1 tow (reinforcing fiber) and a coating film provided so as to cover at least a part of the surface of the tow. The coating film comprises a rubber component, an isocyanate compound, a bismaleimide compound, carbon black and a rubber-modified epoxy resin, wherein the rubber component comprises at least one selected from carboxyl-modified nitrile rubber and carboxyl-modified hydrogenated nitrile rubber.

The method for manufacturing the reinforcing cord of the present embodiment will be described in more detail below.

In the rubber reinforcing cord of the present embodiment, the filament bundle constituting the cord includes a plurality of filaments. The material of the filament is not particularly limited. As the yarn of the rubber reinforcing yarn in the present embodiment, for example, a glass fiber yarn, a polyvinyl alcohol fiber yarn typified by vinylon fiber, a polyester fiber yarn, a polyamide fiber yarn such as nylon or aramid fiber (aromatic polyamide), a carbon fiber yarn, a poly-p-Phenylene Benzobisoxazole (PBO) fiber yarn, or the like can be used. Among these, filaments of fibers excellent in dimensional stability, tensile strength, modulus and bending fatigue resistance are preferably used. It is preferable to use, for example, at least 1 kind of filament selected from the group consisting of glass filament, aramid filament, polyparaphenylene benzobisoxazole filament and carbon filament, and it is particularly preferable to use glass filament. The tow may be composed of 1 kind of filament or a plurality of kinds of filaments.

The number of filaments contained in the tow is not particularly limited. The tow may contain, for example, in the range of 200 to 24000 filaments.

The surface of the filaments included in the tow may be pretreated for improving the bonding strength. One preferable example of the pretreatment agent is a compound containing at least any 1 functional group selected from an epoxy group and an amino group. Examples of the pretreatment agent include aminosilane, epoxysilane, novolac type epoxy resin, bisphenol a type epoxy resin, bisphenol F type epoxy resin, brominated epoxy resin, bisphenol AD type epoxy resin, glycidylamine type epoxy resin, and the like. Specific examples thereof include the Denacol series by Nagase ChemteX, the EPICLON series by DIC, and the Epikote series by Mitsubishi chemical corporation. Further, as the pretreatment agent, a polyurethane resin and an isocyanate compound can be similarly used. For example, a treatment agent containing at least one selected from the group consisting of an epoxy resin, a urethane resin, and an isocyanate compound may be used as the pretreatment agent. By performing a pretreatment using such a treating agent, a resin layer containing at least one selected from the group consisting of an epoxy resin, a urethane resin, and an isocyanate compound is further provided between the tow and the coating film. By pretreating the surface, the adhesiveness between the matrix rubber and the rubber reinforcing cord can be improved even when a fiber such as a poly (p-phenylene terephthalamide) fiber is used, for example, which hardly exhibits adhesion. A coating film (pretreatment agent film) containing a pretreatment agent formed on the surface of a yarn by pretreatment of the yarn is different from a coating film covering at least a part of the surface of the yarn bundle as specified in the present embodiment, and is not included in the coating film specified in the present embodiment.

The number of strands contained in the rubber reinforcing cord is not limited, and may be 1 or more. The tow may be a product obtained by bundling a plurality of tows. In this case, the plurality of tows may or may not be twisted. Further, the plurality of tows may or may not be twisted in a combined state.

The coating film is provided so as to cover at least a part of the surface of the tow. The coating film may be provided directly on the surface of the tow, or may cover the surface of the tow with another layer interposed therebetween. In the rubber reinforcing cord of the present embodiment, a coating film other than the coating film may not be further provided. As described above, the "other coating film" herein does not include the pretreatment agent coating film described above. Therefore, even if the coating film is provided on the rubber reinforcing cord including the surface of the filament bundle provided with the yarn having the pretreatment agent film, the rubber reinforcing cord may be "a rubber reinforcing cord provided with no coating film other than the coating film".

The coating is formed by supplying an aqueous coating treatment agent described later to at least a part of the surface of the tow and drying the aqueous coating treatment agent by heat treatment. The supply of the aqueous treatment agent to the surface of the tow can be carried out, for example, by impregnating the tow with the aqueous treatment agent for coating or by applying the aqueous treatment agent for coating to at least a part of the surface of the tow. In this case, the heat treatment substantially removes the moisture contained in the yarn itself and the solvent (e.g., water) of the aqueous treatment agent.

The coating contains a rubber component. The rubber component contains at least one selected from the group consisting of a carboxyl-modified nitrile rubber (X-NBR) and a carboxyl-modified hydrogenated nitrile rubber (X-HNBR). The rubber component preferably contains 70 mass% or more of the total amount of the carboxyl-modified nitrile rubber and the carboxyl-modified hydrogenated nitrile rubber, and more preferably 90 mass% or more. The rubber component may consist of only carboxyl-modified nitrile rubber and/or carboxyl-modified hydrogenated nitrile rubber. That is, the total amount of the carboxyl-modified nitrile rubber and the carboxyl-modified hydrogenated nitrile rubber in the rubber component may be 100% by mass. The coating film may further contain a rubber other than the carboxyl-modified nitrile rubber and the carboxyl-modified hydrogenated nitrile rubber. Examples of rubbers other than the carboxyl-modified nitrile rubber and the carboxyl-modified hydrogenated nitrile rubber include butadiene-styrene copolymer, dicarboxylated butadiene-styrene polymer, vinylpyridine-butadiene-styrene terpolymer, chloroprene, butadiene rubber, chlorosulfonated polyethylene, acrylonitrile-butadiene copolymer, nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), and the like.

The coating film further contains an isocyanate compound. The content of the isocyanate compound in the coating film is 10 to 50 parts by mass, preferably 20 to 40 parts by mass, and more preferably 25 to 35 parts by mass, per 100 parts by mass of the rubber component. Examples of the isocyanate compound include aromatic or aliphatic organic diisocyanates, polyisocyanates, blocked isocyanates, and blocked polyisocyanates.

The coating film further contains a bismaleimide compound. The content of the bismaleimide compound in the coating film is 5 to 25 parts by mass, preferably 10 to 20 parts by mass, and more preferably 12 to 18 parts by mass, per 100 parts by mass of the rubber component. Examples of the bismaleimide-based compound include bismaleimide, phenylmaleimide, and N, N' -m-phenylenedimaleimide.

The coating film further contains carbon black. The content of carbon black in the coating film is 2 to 18 parts by mass, preferably 5 to 15 parts by mass, and more preferably 7 to 13 parts by mass, per 100 parts by mass of the rubber component.

The cover film further contains a rubber-modified epoxy resin. The content of the rubber-modified epoxy resin in the coating film is 5 to 30 parts by mass, preferably 10 to 25 parts by mass, and more preferably 12 to 20 parts by mass, per 100 parts by mass of the rubber component. Examples of the rubber-modified epoxy resin include a nitrile-butadiene rubber (NBR) -modified epoxy resin, a butadiene rubber-modified epoxy resin, and the like. Among them, NBR-modified epoxy resins are preferable.

The coating film can achieve fiber protection performance, high adhesion performance, and bending fatigue resistance even by itself by containing a rubber component, an isocyanate compound, a bismaleimide compound, carbon black, and a rubber-modified epoxy resin so as to satisfy the content ranges described above, and by including at least one selected from the group consisting of a carboxyl-modified nitrile rubber and a carboxyl-modified hydrogenated nitrile rubber in the rubber component. In particular, when the reinforcing cord of the present embodiment is applied to a rubber product whose matrix rubber contains hydrogenated nitrile rubber, good adhesion between the coating and the matrix rubber can be obtained. It can be considered that: good adhesion between the coating and the matrix rubber is obtained due to the compatibility of the rubber-modified epoxy resin contained in the coating of the present embodiment with the nitrile rubber of the rubber component contained in the coating and the nitrile rubber contained in the matrix rubber on the rubber product side. Further, it is considered that: the reason why the adhesion between the coating and the matrix rubber is improved is that the epoxy resin reacts with the carboxyl group of the rubber component contained in the coating, and that the hydrogenated nitrile rubber of the matrix rubber on the rubber product side reacts with the carboxyl group contained in the carboxyl group-modified hydrogenated nitrile rubber to form a network structure in the case where the hydrogenated nitrile rubber is, for example, a carboxyl group-modified hydrogenated nitrile rubber. In addition, when the NBR modified epoxy resin is used as the rubber modified epoxy resin, a coating film having further improved flexibility can be obtained, and the bending fatigue resistance of the reinforcing cord can be further improved. The rubber-modified epoxy resin reacts with the isocyanate compound, contributing to more firmly bonding the coating films to each other. Further, the rubber-modified epoxy resin promotes the polymerization reaction of the bismaleimide compound, and the network structure formed in the coating film can be made denser. In this manner, the rubber-modified epoxy resin can be used in combination with the isocyanate compound and the bismaleimide compound to improve the strength of the coating film and the adhesiveness.

The total amount of the isocyanate compound, the bismaleimide compound, the carbon black and the rubber-modified epoxy resin is preferably 100 parts by mass or less with respect to 100 parts by mass of the rubber component. If the total amount of the isocyanate compound, the bismaleimide compound, the carbon black and the rubber-modified epoxy resin exceeds 100 parts by mass, the coating may be difficult, and the protection of the wire and the improvement of the bending fatigue resistance may be hindered.

The coating is preferably free of resorcinol-formaldehyde condensates. When the coating does not contain a resorcinol-formaldehyde condensate, it is not necessary to use a substance having a large environmental load such as formaldehyde or ammonia in the production of the coating. Therefore, no environmental measures are required for the operator.

The coating film may further contain other components in addition to the above components.

The total content of the rubber component, the isocyanate compound, the bismaleimide compound, the carbon black and the rubber-modified epoxy resin (hereinafter, may be simply referred to as "5 components") in the coating film is not particularly limited. The total content of the 5 components in the coating is preferably 70% by mass or more, and more preferably 90% by mass or more. The coating film may be formed substantially from only the above 5 components. The substantially only 5 components means that the total content of the 5 components in the coating film is 97% by mass or more. Further, the coating film may be formed of only the above 5 components.

The quality of the coating film provided on at least the surface of the tow is not particularly limited, and may be appropriately adjusted. For example, the coating is preferably provided so as to be within a range of 5 to 30 mass%, more preferably within a range of 10 to 25 mass%, and particularly preferably within a range of 13 to 19 mass% with respect to the entire reinforcing cord. When the mass% of the coating film is too large, there may be a case where the dimensional stability of the rubber reinforcing cord in the rubber product is lowered and the elastic modulus of the rubber reinforcing cord is lowered. On the other hand, if the mass of the coating film is too small, the strands may easily become loose or the function of protecting the fibers with the coating film may be reduced, which may result in a reduction in the life of the rubber product.

The number of twists of the rubber-reinforcing cord of the present embodiment is not particularly limited. The number of twists (hereinafter sometimes referred to as primary twists) applied to 1 strand may be, for example, in the range of 1 to 6 times/25 mm. Further, the number of twists (hereinafter, also referred to as double twists) applied to the plurality of strands may be, for example, in the range of 1 to 8 times/25 mm. The first twist direction and the second twist direction can be the same forward twist, and the first twist direction and the second twist direction can also be reverse common twist. The twisting direction is not limited, and may be the S direction or the Z direction.

[ method for producing rubber-reinforcing cord ]

An example of the method for producing the rubber reinforcing cord of the present embodiment is described below. Note that, the matters described for the rubber reinforcing cord of the present embodiment can be applied to the following manufacturing method, and therefore, the overlapping description may be omitted. Note that the matters described in the following manufacturing method can be applied to the rubber reinforcing cord of the present embodiment. An example of the manufacturing method includes the following steps.

First, a plurality of filaments are bundled to produce a tow, and an aqueous coating treatment agent for producing a coating is prepared. Next, an aqueous coating treatment agent is supplied to at least a part of the surface of the tow. Thereafter, a heat treatment for removing the solvent in the aqueous coating treatment agent is performed.

Through the above steps, a coating is formed on at least a part of the surface of the tow. The method of supplying the aqueous coating treatment agent to at least a part of the surface of the tow is not limited, and for example, the aqueous coating treatment agent may be applied to the surface of the tow or the tow may be immersed in the aqueous coating treatment agent.

The heat treatment conditions for removing the solvent of the aqueous coating treatment agent are not particularly limited, and drying under such conditions that the reaction of the crosslinking agent in the coating is completely carried out is not to be avoided. Therefore, when drying is performed at a relatively high temperature (for example, 80 ℃ or higher), it is preferable to set the drying time to a short time (for example, 5 minutes or less). For example, in the case of an atmosphere of 150 ℃ or lower, the drying time may be set to 5 minutes or less. In one example, the drying is carried out in an atmosphere of 80 to 280 ℃ for 0.1 to 2 minutes.

The tow having the coating film formed thereon may be twisted in one direction. The twisting direction may be the S direction or the Z direction. The number of filaments included in the tow and the number of twists of the tow are as described above, and therefore, the description thereof is omitted. In this way, the rubber reinforcing cord of the present embodiment can be manufactured. It is also possible to form a plurality of bundles of filaments on which a coating film is formed, and bundle the plurality of bundles and apply a double twist. The direction of the secondary twist may be the same as or different from the twisting direction (primary twist direction) of the tow. In addition, a plurality of tows on which the coating film is formed may be formed, and the plurality of tows may be laid and twisted without being twisted separately.

The coating may be formed after twisting the tow. The types, the numbers, and the twist numbers of the filaments are as described above.

In a preferred example of the production method of the present embodiment, the yarn bundle is coated or impregnated with the aqueous coating agent, and then the bundled product is twisted in one direction to form the rubber reinforcing cord.

Next, the aqueous treating agent for coating will be described.

The aqueous coating treatment agent preferably contains a latex of rubber constituting the rubber component of the coating. The rubber component of the coating film comprises at least 1 rubber selected from the group consisting of carboxyl-modified nitrile rubber (X-NBR) and carboxyl-modified hydrogenated nitrile rubber (X-HNBR), and therefore the aqueous treating agent for coating film comprises a latex of at least 1 rubber selected from the group consisting of carboxyl-modified nitrile rubber (X-NBR) and carboxyl-modified hydrogenated nitrile rubber (X-HNBR). The aqueous treatment agent for coating may further contain other rubber latex depending on the rubber component of the coating.

The aqueous treating agent for coating film further contains an isocyanate compound, a bismaleimide compound, carbon black and a rubber-modified epoxy resin. These components contained in the aqueous coating treatment agent are the same as those described above, and therefore, the description thereof is omitted here. In order to be uniformly present in the aqueous treatment agent, these components are preferably used in the form of an aqueous dispersion.

The aqueous coating treatment agent preferably does not contain a resorcinol-formaldehyde condensate.

The aqueous coating treatment agent may further contain other components than the above. For example, the aqueous coating treatment agent may further contain a resin, a plasticizer, an antioxidant, a stabilizer, a filler, and the like as other components.

[ rubber products ]

The rubber product of the present embodiment is a rubber product reinforced with the rubber reinforcing cord of the present embodiment. The rubber product is not particularly limited. Examples of the rubber product of the present embodiment include tires and transmission belts of automobiles and bicycles. Examples of the transmission belt include a meshing transmission belt, a friction transmission belt, and the like. Examples of the engaging transmission belt include a toothed belt typified by a timing belt for an automobile or the like. Examples of friction drive belts include flat belts, circular belts, V-ribbed belts, and the like. That is, the rubber product of the present embodiment may be a toothed belt, a flat belt, a circular belt, a V-belt, or a V-ribbed belt.

The rubber product of the present embodiment is formed by embedding the rubber reinforcing cord of the present embodiment in a rubber composition (matrix rubber). The method for embedding the rubber reinforcing cord in the matrix rubber is not particularly limited, and a known method can be applied. The rubber product (for example, a rubber belt) according to the present embodiment has the rubber reinforcing cord according to the present embodiment embedded therein. Therefore, the rubber product of the present embodiment has high bending fatigue resistance. Therefore, the rubber product of the present embodiment is particularly suitable for applications such as a synchronous belt of an engine for a vehicle, a belt for driving auxiliary machines for a vehicle, and the like.

The rubber contained in the rubber composition in which the rubber reinforcing cord of the present embodiment is embedded is not particularly limited, but is preferably hydrogenated nitrile rubber. As described above, this is because the coating film of the rubber-reinforcing cord of the present embodiment can maintain flexibility and achieve bending fatigue resistance and improve adhesion when used in combination with a matrix rubber containing hydrogenated nitrile rubber. The hydrogenated nitrile rubber may be a hydrogenated nitrile rubber in which a zinc acrylate derivative (e.g., zinc methacrylate) is dispersed. From the viewpoint of water resistance and oil resistance, at least 1 rubber selected from the group consisting of hydrogenated nitrile rubbers and hydrogenated nitrile rubbers in which zinc acrylate derivatives are dispersed is preferable. The matrix rubber may further comprise a hydrogenated nitrile rubber modified with carboxyl groups.

Fig. 1 shows a toothed belt as an example of a rubber product. The toothed belt 1 shown in fig. 1 includes a belt main body 11 and a plurality of rubber reinforcing cords 12. The belt body 11 includes a belt portion 13 and a plurality of teeth 14 projecting from the belt portion 13 at fixed intervals. The rubber reinforcing cord 12 is embedded inside the belt portion 13 so as to be parallel to the longitudinal direction of the belt portion 13. The rubber reinforcing cord 12 is the rubber reinforcing cord of the present embodiment.