JP2021105243A - Rubber-reinforcing cord and rubber product using the same - Google Patents

Abstract

To provide a rubber-reinforcing cord that includes a polyparaphenylene terephthalamide fiber as a reinforcing fiber and achieves both of high tensile strength and high adhesive strength.SOLUTION: A rubber-reinforcing cord 12 according to the present invention is a rubber-reinforcing cord for reinforcing a rubber product 1 and includes at least one strand. The strand includes at least one filament bundle and a first film that is provided so as to cover at least a portion of the surface of the filament bundle. The filament bundle is substantially formed of polyparaphenylene terephthalamide fiber filaments. The first film contains a rubber component and a crosslinking agent. The rubber-reinforcing cord further contains a liquid component, and the liquid-component content in the rubber-reinforcing cord is in the range of 0.1 to 2.0 mass%.SELECTED DRAWING: Figure 1

Description

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

As a reinforcing material for rubber products such as rubber belts and tires that are repeatedly subjected to bending stress, a rubber reinforcing cord formed by using tough fibers is widely used. Since the rubber reinforcing cord is used as a tension body for enhancing the dimensional stability of the rubber product, it requires high tensile strength.

The manufacturing process of the rubber reinforcing cord generally includes a step of applying a treatment agent containing resorcin, formaldehyde, and rubber latex (RFL) to the fiber and drying it (RFL treatment step). Further, as the treatment agent to be applied to the fiber, a treatment agent containing a material crosslinked by heat treatment and not containing a resorcin-formaldehyde condensate may be used. Due to the coating formed by such a treatment agent, the rubber reinforcing cord can improve the adhesiveness with the matrix rubber when embedded in the rubber composition (matrix rubber) constituting the rubber product.

Examples of the fiber used for the rubber reinforcing cord include aramid fiber. Aramid fiber is generally a fiber having high strength and high elastic modulus, and is widely used as a reinforcing cord for a rubber belt for power transmission. Rubber reinforcing cords obtained by treating aramid fibers with a treatment agent containing RFL have been proposed, for example, in Patent Documents 1 to 3. Further, a rubber reinforcing cord obtained by treating an aramid fiber with a treatment agent containing a material crosslinked by heat treatment and not containing a resorcin-formaldehyde condensate has been proposed in Patent Document 4, for example.

Japanese Unexamined Patent Publication No. 8-100370 Special Table 2005-517097 JP-A-2010-95814 Patent No. 4217058

However, among the aramid fibers, the polyparaphenylene terephthalamide fiber known as the para-type aramid fiber has a problem that the tensile strength is significantly lowered by the heat treatment when the treatment agent is dried. In particular, the tensile strength is greatly reduced by heating during the RFL treatment step. On the other hand, in order to obtain good adhesive strength between the rubber reinforcing cord and the matrix rubber, it is necessary to provide a sufficient amount of heat for the RFL reaction in the heat treatment during the RFL treatment step. Therefore, if the amount of heat applied during the RFL treatment step is kept small, the decrease in tensile strength can be kept small, but this causes a problem that sufficient adhesive strength between the matrix rubber and the rubber reinforcing cord cannot be obtained. When a treatment agent containing a material crosslinked by heat treatment and not containing a resorcin-formaldehyde condensate is used, the amount of heat applied may be reduced as compared with the case of using a treatment agent containing RFL, but the matrix rubber is still used. When the amount of heat required to obtain sufficient adhesive strength between the rubber and the rubber reinforcing cord is applied, a decrease in tensile strength is unavoidable. As described above, it has been difficult to obtain a rubber reinforcing cord having both high tensile strength and high adhesive strength by using polyparaphenylene terephthalamide fiber.

Therefore, one of the objects of the present invention is to obtain a rubber reinforcing cord containing polyparaphenylene terephthalamide fiber as a reinforcing fiber and having both high tensile strength and high adhesive strength. Furthermore, one of the other objects of the present invention is a high-strength rubber reinforced by such a rubber reinforcing cord, which has a high tensile strength and also a high adhesive strength between the matrix rubber and the rubber reinforcing cord. To provide a product.

After diligent research, the present inventor uses polyparaphenylene terephthalamide fiber as a reinforcing fiber, and in the case of a rubber reinforcing cord obtained by forming a film on the surface of this fiber using a treatment agent, rubber reinforcement is performed. The ratio of the liquid component remaining in the cord (such as the solvent of the treatment agent and the water contained in the fiber) affects the tensile strength of the rubber reinforcing cord and the adhesive strength of the rubber reinforcing cord to the matrix rubber. We have reached the following rubber reinforcing cord of the present invention that can achieve both high tensile strength and high adhesive strength.

The present invention is a rubber reinforcing cord for reinforcing a rubber product.
The rubber reinforcing cord comprises at least one strand and
The strands include at least one filament bundle and a first coating provided to cover at least a portion of the surface of the filament bundle.
Includes
The filament bundle is substantially composed of polyparaphenylene terephthalamide fiber filaments.
The first coating contains a rubber component and a cross-linking agent, and contains a rubber component and a cross-linking agent.
The rubber reinforcing cord further contains a liquid component, and the content of the liquid component in the rubber reinforcing cord is in the range of 0.1 to 2.0% by mass.

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

According to the present invention, even when a polyparaphenylene terephthalamide fiber is used as a reinforcing fiber, a rubber reinforcing cord having both high tensile strength and high adhesive strength with a matrix rubber is provided. can. Further, since the rubber product of the present invention is reinforced with such a rubber reinforcing cord, high tensile strength and high adhesive strength between the matrix rubber and the rubber reinforcing cord can be realized.

It is a partially disassembled perspective view schematically showing an example of the rubber product of this invention.

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

[Rubber reinforcement cord]
The rubber reinforcing cord of the present embodiment is a cord for reinforcing a rubber product. The rubber reinforcing cord comprises at least one strand. The strands include at least one filament bundle and a first coating provided to cover at least a portion of the surface of the filament bundle. The filament bundle consists substantially of polyparaphenylene terephthalamide fiber filaments. The first coating contains a rubber component and a cross-linking agent. The rubber reinforcing cord of the present embodiment further contains a liquid component, and the content of the liquid component in the rubber reinforcing cord is in the range of 0.1 to 2.0% by mass. The liquid component contained in the rubber reinforcing cord is, for example, a solvent contained in the aqueous treatment agent (first aqueous treatment agent for coating) used when producing the first coating, or water contained in the filament itself. It is composed of the residuals such as.

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

In the rubber reinforcing cord of the present embodiment, the filament bundle constituting the strand includes a plurality of filaments. As mentioned above, the filament bundle is substantially composed of polyparaphenylene terephthalamide fiber filaments. Here, "the filament bundle is substantially composed of a polyparaphenylene terephthalamide fiber filament" means that the filament bundle is a filament other than the polyparaphenylene terephthalamide fiber filament to the extent that the effect of the invention is not significantly affected. It means that it may be included. For example, the filament bundle may contain filaments other than the polyparaphenylene terephthalamide fiber filament at a ratio of 10% or less (for example, 5% or less or 1% or less) in the cross-sectional area of the filament bundle. Examples of the polyparaphenylene terephthalamide fiber include "Twaron" manufactured by Teijin Limited and "Kevlar" manufactured by Toray DuPont Co., Ltd. As the filament other than the polyparaphenylene terephthalamide fiber filament, a filament of a fiber generally used as a fiber for reinforcing a rubber reinforcing cord can be used. The filament bundle may consist solely of polyparaphenylene terephthalamide fibers.

The number of filaments contained in the filament bundle is not particularly limited. The filament bundle can include, for example, 200 to 2000 filaments.

The surface of the polyparaphenylene terephthalamide fiber filament contained in the filament bundle is preferably pretreated to increase the adhesive strength. A preferred example of a pretreatment agent is a compound containing at least one functional group selected from the group consisting of an epoxy group and an amino group. Examples of pretreatment agents include aminosilane, epoxysilane, novolak 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 include the Denacol series of Nagase ChemteX Corporation, the Epicron series of DIC Corporation, and the Epicoat series of Mitsubishi Chemical Corporation. Further, as the pretreatment agent, a polyurethane resin and an isocyanate compound can also be used in the same manner. For example, as the pretreatment agent, 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. By pretreating with such a treatment agent, a resin layer containing at least one selected from the group consisting of an epoxy resin, a urethane resin and an isocyanate compound between the filament bundle and the first coating film. Is further provided. By using a polyparaphenylene terephthalamide fiber filament whose surface has been pretreated, it is possible to improve the adhesiveness between the matrix rubber and the rubber reinforcing cord.

The number of filament bundles included in the rubber reinforcing cord is not limited, and may be one or a plurality of filament bundles. The filament bundle may be a bundle of a plurality of filament bundles. In this case, each of the plurality of filament bundles may or may not be twisted. Further, a plurality of filament bundles may or may not be twisted in a combined state.

The first coating is provided so as to cover at least a part of the surface of the filament bundle. The first coating film may be provided directly on the surface of the filament bundle, or may be provided through another layer (for example, a coating film formed by the above-mentioned filament pretreatment (for example, the above-mentioned resin layer)). May cover the surface of the filament bundle.

The first coating film is formed by supplying at least a part of the surface of the filament bundle with the first aqueous treatment agent for coating film described later and drying it by heat treatment. The supply of the first aqueous treatment agent to the surface of the filament bundle is, for example, impregnating the first aqueous treatment agent for coating with the filament bundle, or impregnating at least a part of the surface of the filament bundle with the first aqueous treatment for coating. It can be carried out by applying a treatment agent. The heat treatment at this time substantially removes the water content of the filament itself and the solvent (for example, water) of the aqueous treatment agent.

The first coating contains a rubber component. The rubber component preferably contains at least one selected from the group consisting of nitrile rubber, hydrogenated nitrile rubber, carboxyl-modified nitrile rubber and carboxyl-modified hydrogenated nitrile rubber. The first coating film may contain only one type of the rubber as a rubber component, or may contain a plurality of types of the rubber. These rubbers are preferable because they have little swelling due to oil and are excellent in oil resistance. In the present specification, the term "nitrile rubber" means a nitrile rubber (acrylonitrile-butadiene copolymer rubber) that has not been hydrogenated or carboxyl-modified unless otherwise specified. The iodine value of hydrogenated nitrile rubber is usually 120 or less, and may be 100 or less, for example. The iodine value of an example hydrogenated nitrile rubber is in the range of 0 to 50.

The first coating film may contain other rubbers in addition to the above rubbers. Examples of other rubbers include butadiene / styrene copolymers, dicarboxylated butadiene / styrene copolymers, vinylpyridine / butadiene / styrene copolymers, chloroprene rubbers, butadiene rubbers and chlorosulfonated polyethylenes.

The first coating further contains a cross-linking agent. Since the first film contains a cross-linking agent, the rubber reinforcing cord of the present embodiment can improve the adhesiveness with the matrix rubber. Examples of cross-linking agents include quinone-dioxime-based cross-linking agents such as P-quinone dioxime, methacrylate-based cross-linking agents such as lauryl methacrylate and methyl methacrylate, DAF (diallyl fumarate), DAP (diallyl phthalate), and TAC. Allyl-based cross-linking agents such as (triallyl cyanurate) and TAIC (triallyl isocyanurate), maleimide-based cross-linking agents such as bismaleimide, phenylmaleimide and N, N'-m-phenylenedimaleimide, aromatic or aliphatic. Includes organic diisocyanates, polyisocyanates, blocked isocyanates, blocked polyisocyanates, aromatic nitroso compounds, sulfur, and peroxides. These cross-linking agents may be used alone or in combination of two or more. These cross-linking agents are selected in consideration of the type of rubber contained in the first coating film, the type of matrix rubber in which the rubber reinforcing cord is embedded, and the like. It is preferable that these cross-linking agents are used in the form of an aqueous dispersion in order for the cross-linking agent to be uniformly present in the aqueous treatment agent for producing the first coating film. The cross-linking agent may be at least one selected from the group consisting of maleimide-based cross-linking agents, organic diisocyanates, and aromatic nitroso compounds.

Among the above-mentioned cross-linking agents, it is preferable to use at least one selected from the group consisting of maleimide-based cross-linking agents and polyisocyanates. Among the maleimide-based cross-linking agents, 4,4'-bismaleimide diphenylmethane is preferably used because it has good stability when dispersed in water, has a high cross-linking effect, and has high heat resistance after cross-linking. By combining the maleimide-based cross-linking agent and the polyisocyanate with the rubber latex, the adhesiveness between the reinforcing cord and the matrix rubber can be specifically enhanced. In particular, a combination of a carboxyl-modified hydrogenated nitrile rubber latex and a maleimide-based cross-linking agent is preferable because the adhesiveness can be further enhanced.

The first coating may further contain a filler. Examples of fillers include fine particles of covalent bond compounds such as carbon black and silica, fine particles of sparingly soluble salts, fine particles of metal oxides, fine particles of metal hydroxides, and fine particles of composite metal oxide salts such as talc. included. Among these, at least one selected from the group consisting of carbon black and silica is preferable.

The average particle size of carbon black is preferably in the range of 5 to 300 nm, for example in the range of 100 to 200 nm, and more preferably in the range of 130 to 170 nm. The average particle size of silica is preferably in the range of 5 to 200 nm, for example in the range of 7 to 100 nm, and more preferably in the range of 7 to 30 nm. Here, the average particle size is a value obtained by measuring the particle size of 50 or more particles using a transmission electron microscope and dividing the total particle size by the number of measured particles. When the particles were not spherical, the average of the longest diameter and the shortest diameter of each particle was taken as the particle size.

Since the filler is dispersed in the rubber, it has an effect of improving properties such as tensile strength and tear strength of the coating film. In addition to these effects, the filler also has an effect of improving the adhesive strength by increasing the cohesive force of the adhesive component between the fiber and the coating film and between the coating film and the matrix rubber. It should be noted that the particle size and the blending amount of the filler have a great influence on these effects.

The first coating preferably does not contain a resorcin-formaldehyde condensate. In that case, when producing the first film, it is not necessary to use substances having a large environmental load such as formaldehyde and ammonia, so that environmental measures for workers become unnecessary. However, the first coating may contain a resorcin-formaldehyde condensate.

The first coating further contains a filler and other components (for example, a metal oxide other than the metal oxide added as the filler, a resin, etc.) in addition to the rubber component and the cross-linking agent. You may.

The content of the rubber component and the cross-linking agent in the first coating film is not particularly limited. The content of the rubber component in the first coating film can be, for example, 50 to 90% by mass. Further, the content of the cross-linking agent in the first coating film can be in the range of, for example, 10 to 50% by mass.

The mass of the first coating film provided on at least the surface of the filament bundle is not particularly limited and may be appropriately adjusted, but it is preferably provided so as to be within the range of 5 to 35% of the mass of the filament bundle. The mass of the first coating film may be in the range of 10 to 25% by mass of the filament bundle, or may be in the range of 12 to 20% by mass. If the mass of the first coating film is too large, problems such as a decrease in dimensional stability of the rubber reinforcing cord in the rubber product and a decrease in the elastic modulus of the rubber reinforcing cord may occur. On the other hand, if the mass of the first coating is too small, the strands may easily fray, or the function of protecting the fibers by the first coating may be reduced, and as a result, the life of the rubber product may be shortened. ..

In order to improve the adhesiveness with the matrix rubber, the rubber reinforcing cord of the present embodiment may further include a second coating formed on the first coating. The treatment agent for forming the second film may be the same as or different from the water-based treatment agent for the first film. For example, the second coating may be formed with a treatment agent whose component or solvent is different from that of the first aqueous treatment agent for coating. It is also possible to provide a further coating on the second coating in order to further improve the adhesion to the matrix rubber.

The number of twists of the rubber reinforcing cord of the present embodiment is not particularly limited. The number of twists (hereinafter, also referred to as lower twists) applied to one strand is, for example, in the range of 20 to 160 times / m, in the range of 30 to 120 times / m, or 40 to 100 times / m. It may be a range. Further, the number of twists added to the plurality of strands (hereinafter, also referred to as top twists) is similarly, for example, in the range of 20 to 160 times / m, in the range of 30 to 120 times / m, or 40 to 100 times. It may be in the range of times / m. It may be a rung twist in which the lower twist direction and the upper twist direction are the same, or a Moro twist in which the lower twist direction and the upper twist direction are opposite to each other. The twisting direction is not limited, and may be the S direction or the Z direction.

The content of the liquid component in the rubber reinforcing cord of the present embodiment is in the range of 0.1 to 2.0% by mass. As described above, the liquid component is a residue of the solvent (for example, water) contained in the aqueous treatment agent used when forming the film, the water content of the filament itself, and the like. In the rubber reinforcing cord of the present embodiment, in the heat treatment for producing the first coating film, further, when the rubber reinforcing cord of the present embodiment further includes the second coating film, a second coating film is produced. In the heat treatment, the tension of the polyparaphenylene terephthalamide fiber is obtained by adjusting the amount of heat so that the liquid component remains in the rubber reinforcing cord within the range of 0.1 to 2.0% by mass. Sufficient adhesive strength with the rubber matrix can be realized while suppressing the decrease in strength or suppressing the degree of decrease to a small degree. The content of the liquid component is less than 0.1% by mass, that is, the heat treatment at the time of forming the first film and the heat treatment at the time of forming the second film are contained in the solvent of the treatment agent for forming the film and the fiber. If it is carried out so that almost all of the water is removed, the tensile strength of the polyparaphenylene terephthalamide fiber is reduced, and as a result, the tensile strength of the rubber reinforcing cord is reduced. On the other hand, when the content of the liquid component exceeds 2.0% by mass, it means that a sufficient amount of heat has not been applied to the coating film so as to realize sufficient adhesive strength with the matrix rubber. It is not possible to obtain a rubber reinforcing cord that can achieve sufficient adhesive strength.

In order to obtain a rubber reinforcing cord having higher tensile strength and higher adhesive strength, the content of the liquid component in the rubber reinforcing cord is preferably 0.2 to 1.5% by mass, and is 0. More preferably, it is 3 to 1.3% by mass.

Here, the "content rate of the liquid component in the rubber reinforcing cord" specified in the present invention is a value obtained as follows. A cord having a length of 5 m is taken as a sample from the rubber reinforcing cord, the sample is measured with an electronic balance, and this value is defined as the mass A of the cord. The sample was placed in a dryer heated to 150 ° C. for 30 minutes to remove the solvent in the sample, placed in a desiccator for 30 minutes, and then the value measured by an electronic balance was taken as mass B, and the difference between mass A and mass B was taken. Was defined as the mass (AB) of the liquid component contained in the cord. The percentage ({(AB) / A} × 100) of the mass (AB) of the liquid component contained in the cord with respect to the mass A of the cord is defined as the content ratio (%) of the liquid component. Here, assuming that the solvent of the treatment agent is water, heat treatment is performed at 150 ° C. for 30 minutes in order to completely remove water from the sample, but a solvent other than water is used. If so, an appropriate heating temperature and heating time may be set so that the solvent can be completely removed.

If the rubber reinforcing cord further includes a second coating provided on the first coating, heat treatment will also be performed when the second coating is produced. Therefore, it is preferable that the heat treatment for producing the second coating is also carried out within a range that prevents a decrease in tensile strength and adhesive strength, and in that case, the second coating is applied to the liquid component in the rubber reinforcing cord. It may contain a liquid such as a solvent remaining in the heat treatment. Therefore, in the case of the rubber reinforcing cord containing the second coating film, the content of the liquid component in the rubber reinforcing cord is preferably in the range of 0.5 to 2.0% by mass.

[Manufacturing method of rubber reinforcement cord]
An example of the method for manufacturing the rubber reinforcing cord of the present embodiment will be described below. Since the items described for the rubber reinforcing cord of the present embodiment can be applied to the following manufacturing methods, duplicate explanations may be omitted. In addition, the matters described in the following manufacturing method can be applied to the rubber reinforcing cord of the present embodiment. An example of this manufacturing method includes the following steps.

First, a plurality of filaments are bundled to prepare a filament bundle, and an aqueous treatment agent (first aqueous treatment agent for coating) used for producing the first coating is prepared. Next, the first aqueous treatment agent for coating is supplied to at least a part of the surface of the filament bundle. Then, a heat treatment is performed to remove the solvent in the first aqueous treatment agent for coating film. As a specific example, first, 1000 filaments are aligned to form a bundle, and the surface of the bundle is coated or impregnated with a first aqueous treatment agent for coating. Then, the solvent in the first aqueous treatment agent for coating is removed by heat treatment. The filament bundle consists substantially of polyparaphenylene terephthalamide fiber filaments.

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

The conditions of the heat treatment for removing the solvent of the first aqueous treatment agent for coating film are not particularly limited, but the content of the liquid component of the code obtained after the heat treatment is 0.1 to 2.0% by mass. , The treatment temperature and treatment time are adjusted as appropriate. Preferably, the treatment temperature and the treatment time are appropriately adjusted so that the content of the liquid component of the cord obtained after the heat treatment is 0.2 to 1.5% by mass, more preferably 0.3 to 1.3% by mass. It is to be. The treatment temperature is preferably 220 ° C. or lower, for example. The treatment time is not particularly limited, and the amount of heat applied is within the range specified in the present embodiment (0.1 to 2.0 mass) in consideration of the temperature of the heat treatment and the content of the liquid component in the completed rubber reinforcing cord. %) May be appropriately adjusted so that the amount of heat can be realized.

The filament bundle on which the first coating is formed is usually twisted in one direction. The twisting direction may be the S direction or the Z direction. Since the number of filaments contained in the filament bundle and the number of twists of the filament bundle have been described above, the description thereof will be omitted. In this way, the rubber reinforcing cord of the present embodiment can be manufactured. A plurality of filament bundles on which the first coating is formed may be formed, and the plurality of filament bundles may be bundled and top-twisted. The direction of the upper twist may be the same as or different from the direction of the twist of the filament bundle (the direction of the lower twist). Further, a plurality of filament bundles on which the first film is formed may be formed, and twists may be added to the bundles of the plurality of filament bundles without giving twists to each of the filament bundles.

The first film may be formed after twisting the filament bundle. The type, number, and number of twists of the filament are as described above.

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

When the second film is formed on the first film, a treatment agent for forming the second film is applied on the first film, and the solvent in the treatment agent is removed. The second coating may be formed by. The type of the second coating film can be appropriately selected according to the matrix rubber of the rubber product to which the rubber reinforcing cord is applied, and is particularly desirable from the viewpoint of improving the adhesiveness.

The conditions of the heat treatment for removing the solvent of the second coating treatment agent are not particularly limited, but the content of the liquid component of the cord obtained after the heat treatment is 0.5 to 2.0% by mass. It is preferable to adjust the treatment temperature and the treatment time as appropriate.

Next, the first aqueous treatment agent for coating film will be described.

The first aqueous treatment agent for coating may contain a latex of at least one rubber selected from the group consisting of nitrile rubber, hydrogenated nitrile rubber, carboxyl-modified nitrile rubber, and carboxyl-modified hydrogenated nitrile rubber. preferable. The aqueous treatment agent may contain only one kind of these rubber latexes, or may contain a plurality of kinds of these rubber latexes.

The first aqueous treatment agent for coating may contain other rubber latex in addition to the above rubber latex. Examples of other rubber latexes include butadiene / styrene copolymer latex, dicarboxylated butadiene / styrene copolymer latex, vinylpyridine / butadiene / styrene terpolymer latex, chloroprene latex, butadiene latex, and chlorosulfonated polyethylene latex. included. The aqueous treatment agent may contain a plurality of types of these rubber latexes.

The first aqueous treatment agent for coating further contains a cross-linking agent. Since the cross-linking agent contained in the first aqueous treatment agent for a coating film is the same as that described above as the cross-linking agent contained in the first coating film, the description thereof is omitted here. The cross-linking agent is preferably used in the form of an aqueous dispersion in order to uniformly exist in the aqueous treatment agent.

The first aqueous treatment agent for coating may further contain a filler. Since the filler contained in the first aqueous treatment agent for coating is the same as that described above as the filler contained in the first coating, the description thereof is omitted here.

The first aqueous treatment agent for coatings preferably does not contain a resorcin-formaldehyde condensate. However, the first aqueous treatment agent for coating may contain a resorcin-formaldehyde condensate.

The first aqueous treatment agent for coating may contain a filler and other components in addition to the rubber latex and the cross-linking agent. For example, the first aqueous treatment agent for coating may contain a resin, a plasticizer, an antiaging agent, a stabilizer, a metal oxide other than the metal oxide added as the filler, and the like. However, the aqueous treatment agent may not contain a resin.

[Rubber product]
The rubber product of the present embodiment is a rubber product reinforced with the rubber reinforcing cord of the present embodiment. There are no particular restrictions on rubber products. Examples of rubber products of the present embodiment include tires for automobiles and bicycles, transmission belts, and the like. Examples of transmission belts include meshing transmission belts, friction transmission belts, and the like. Examples of meshing transmission belts include toothed belts such as timing belts for automobiles. Examples of friction transmission belts include flat belts, round belts, V-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 round 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 of embedding the rubber reinforcing cord in the matrix rubber is not particularly limited, and a known method may be applied. The rubber reinforcing cord of the present embodiment is embedded in the rubber product (for example, a rubber belt) of the present embodiment. 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 timing belt for a vehicle engine and a belt for driving an auxiliary machine for a vehicle.

The rubber contained in the rubber composition in which the rubber reinforcing cord of the present embodiment is embedded is not particularly limited, and may be chloroprene rubber, chlorosulfonated polyethylene rubber, ethylene propylene rubber, hydride nitrile rubber, or the like. The hydrogenated nitrile rubber may be a hydrogenated nitrile rubber in which a zinc acrylate derivative (for example, zinc methacrylate) is dispersed. At least one rubber selected from the hydrogenated nitrile rubber and the hydrogenated nitrile rubber in which the zinc acrylate derivative is dispersed is preferable from the viewpoint of water resistance and oil resistance. The matrix rubber may further include a carboxyl-modified hydrogenated nitrile rubber. It is preferable that the coating of the rubber reinforcing cord and the rubber composition of the rubber product contain the same type of rubber or are made of the same type of rubber in terms of adhesiveness.

As an example of a rubber product, a toothed belt is shown in FIG. The toothed belt 1 shown in FIG. 1 includes a belt main body 11 and a plurality of rubber reinforcing cords 12. The belt main body 11 includes a belt portion 13 and a plurality of tooth portions 14 protruding from the belt portion 13 at regular 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.

Hereinafter, embodiments of the present invention will be described in more detail with reference to Examples and Comparative Examples.

[Examples 1 to 10 and Comparative Examples 1 to 6]
<Manufacturing of rubber reinforcement cords>
First, "Kevlar 29" (1670dtex) manufactured by Toray DuPont, which was pretreated with a pretreatment agent containing an epoxy resin, was prepared. 1000 of these "Kevlar 29" were focused and used as a filament bundle. After immersing the filament bundle in the first aqueous treatment agent for coating having the composition shown in Table 1 below, the solvent was evaporated by heat treatment at 200 ° C. to obtain the "content of liquid component" shown in Tables 3 and 4. The first coating was formed so as to be. The solid content of the first aqueous treatment agent for coating was 20% by mass, and the mass of the first coating was 20% of the mass of the filament bundle. The "content of the liquid component" was adjusted by changing the heat treatment time. The first film-coated filament bundle thus produced is down-twisted in a Z-twist at a rate of 40 times / m, and two of them are bundled and twisted up in a Z-twist at a rate of 100 times / m. , Obtained a rubber reinforcement cord. The content of liquid components, tensile strength and adhesive strength of the obtained rubber reinforcing cord were measured. The methods for measuring the content of liquid components, tensile strength and adhesive strength are as follows.

<Liquid component content>
Within 30 minutes after the heat treatment performed after immersing the filament bundle in the first aqueous treatment agent for coating, a cord having a length of 5 m was taken as a sample from the obtained rubber reinforcing cord. The sample was measured with an electronic balance, and this value was taken as the mass A of the code. Next, the sample was placed in a dryer heated to 150 ° C. for 30 minutes to remove the solvent in the sample, placed in a desiccator for 30 minutes, and then the value measured by an electronic balance was taken as mass B. The difference between the mass A and the mass B was defined as the mass (AB) of the liquid component contained in the code. The percentage ({(AB) / A} × 100) of the mass (AB) of the liquid component contained in the cord with respect to the mass A of the cord was determined and used as the content ratio (%) of the liquid component. Tables 3 and 4 show the content of the liquid component of the rubber reinforcing cords of Examples 1 to 10 and Comparative Examples 1 to 6.

<Tensile strength>
The rubber reinforcing cords of each example and comparative example were subjected to a tensile test using a commonly used tensile tester and a commonly used cord grip, and the breaking strength obtained at that time was used as the tensile strength. And said. The breaking strength was measured according to ASTM7269. The unit is N / code. Tables 3 and 4 show the tensile strength of the rubber reinforcing cords of Examples 1 to 10 and Comparative Examples 1 to 6.

<Adhesive strength>
A test piece for an adhesive strength test was prepared by stacking a canvas, a rubber reinforcing cord, and a matrix rubber sheet in this order and pressing at 160 ° C. for 30 minutes. The dimensions of the test piece were 25 mm in width, 150 mm in length, and 3 mm in thickness. In the test piece, the length direction of the rubber reinforcing cord was substantially parallel to the length direction of the test piece. As the matrix rubber, one containing hydrogenated nitrile rubber as a main component having the composition shown in Table 2 was used. Next, the cord and the matrix rubber were grasped, one was fixed, and the other was peeled off in the length direction of the rubber reinforcing cord, and the strength per 25 mm width was measured.

The content of the liquid component of the rubber reinforcing cords of Examples 1 to 10 was in the range of 0.1 to 2.0% by mass. On the other hand, in the rubber reinforcing cord of Comparative Example 1, the content of the liquid component was less than 0.1% by mass because the solvent in the first coating and the water in the filament were completely removed by heat treatment. .. In the rubber reinforcing cords of Comparative Examples 2 to 6, the content of the liquid component exceeded 2.0% by mass. In other words, the rubber reinforcing cord of Comparative Example 1 is subjected to excessive heat treatment beyond the range of heat treatment assumed in order to obtain the rubber reinforcing cord of the present invention, and is subjected to excessive heat treatment in Comparative Examples 2 to 6. The rubber reinforcing cord was subjected to insufficient heat treatment that was less than the range of heat treatment assumed in order to obtain the rubber reinforcing cord of the present invention.

As shown in Table 3, in the rubber reinforcing cords of Examples 1 to 10, both the tensile strength and the adhesive strength were high, the tensile strength was 500 N / cord or more, and the adhesive strength was 150 N / 25 mm or more. On the other hand, as shown in Table 4, in the rubber reinforcing cords of Comparative Examples 1 to 6, either the tensile strength or the adhesive strength was low. In Comparative Example 1, the tensile strength was less than 500 N / cord, and in Comparative Examples 2 to 6, the adhesive strength was less than 150 N / 25 mm. When the adhesive strength was 150 N / 25 mm or more, there was partial rubber breakage at the peeling interface, and when it was less than 150 N / 25 mm, the interface was peeled off in the vicinity of the first coating film. From this result, it was confirmed that the ratio of the liquid component (mainly the solvent of the aqueous treatment agent for the first coating film) remaining in the cord after the formation of the first coating film correlates with the tensile strength and the adhesive strength. rice field.

[Examples 11 to 20 and Comparative Examples 7 to 11]
<Manufacturing of rubber reinforcement cords>
First, a first coating was formed on the surface of the filament bundle in the same manner as in Examples 1 to 10 and Comparative Examples 2 to 6, and the filament bundle with the first coating was Z-twisted at a rate of 40 times / m. The cord was twisted downward, and two of them were bundled to obtain a cord that was twisted upward in Z twist at a rate of 100 times / m. Next, a second coating treatment agent having the composition shown in Table 5 below was applied onto the cord after the top twist and dried to form a second coating. The rubber reinforcing cords obtained by forming a second coating on the upper-twisted cords produced in the same manner as in Examples 1 to 10 and Comparative Examples 2 to 6 were compared with Examples 11 to 20, respectively. The rubber reinforcing cords of Examples 7 to 11 were used. In Examples 11 to 20 and Comparative Examples 7 to 11, the amount of the second coating film was 10% by mass with respect to the cord after the upper twist. The second coating treatment agent was dried at a treatment temperature of 100 ° C. and a treatment time of 2 minutes. The content of the liquid component after forming the second film is in the range of 0.5 to 1.9% by mass as shown in Table 6, and the liquid component of the rubber reinforcing cord is treated for the second film. It is considered that the solvent of the agent is also contained. The content of liquid components, tensile strength and adhesive strength of the obtained rubber reinforcing cord were measured. The method for measuring the content of the liquid component, the tensile strength and the adhesive strength is the same as in Examples 1 to 20 and Comparative Examples 1 to 6. However, the content of the liquid component was measured within 30 minutes after the heat treatment after applying the second coating treatment agent. These results are shown in Tables 6 and 7. Tables 6 and 7 also show the content of the liquid component measured within 30 minutes after the heat treatment when the first film was formed and before the second film was formed.

In the rubber reinforcing cords of Examples 11 to 20, the content of the liquid component after the formation of the second coating film was in the range of 0.5 to 2.0% by mass. The rubber reinforcing cords of Comparative Examples 7 to 11 had a liquid component content of more than 2% by mass. In other words, the rubber reinforcing cords of Comparative Examples 7 to 11 were subjected to insufficient heat treatment that was less than the range of heat treatment assumed for obtaining the rubber reinforcing cord of the present invention.

As shown in Table 6, in the rubber reinforcing cords of Examples 11 to 20, both the tensile strength and the adhesive strength were high, the tensile strength was 500 N / cord or more, and the adhesive strength was 200 N / 25 mm or more. In Comparative Examples 7 to 11, the adhesive strength was less than 200 N / 25 mm even though the second coating film for improving the adhesiveness with the matrix rubber was provided. When the adhesive strength was 200 N / 25 mm or more, the peeling interface was rubber fracture, and when the adhesive strength was less than 200 N / 25 mm, the interface was peeled near the first coating film. That is, it was confirmed that the ratio of the liquid component contained in the rubber reinforcing cord also correlates with the tensile strength and the adhesive strength even in the rubber reinforcing cord provided with the coating of a plurality of layers.

Since the rubber reinforcing cord of the present invention can realize high adhesive strength with matrix rubber and high tensile strength, it can be applied to reinforcing various rubber products. For example, it can be suitably used as a reinforcing cord for a timing belt or the like, which is required to have high heat resistance and bending fatigue resistance. Further, since the rubber product of the present invention can withstand a high load, it can be applied to various uses.

Claims (10)

A rubber reinforcement cord for reinforcing rubber products.
The rubber reinforcing cord comprises at least one strand and
The strands include at least one filament bundle and a first coating provided to cover at least a portion of the surface of the filament bundle.
Includes
The filament bundle is substantially composed of polyparaphenylene terephthalamide fiber filaments.
The first coating contains a rubber component and a cross-linking agent, and contains a rubber component and a cross-linking agent.
The rubber reinforcing cord further contains a liquid component, and the content of the liquid component in the rubber reinforcing cord is in the range of 0.1 to 2.0% by mass.
Rubber reinforcement cord. The rubber reinforcing cord further includes a second coating provided on the first coating.
The content of the liquid component in the rubber reinforcing cord is in the range of 0.5 to 2.0% by mass.
The rubber reinforcing cord according to claim 1. The rubber component comprises at least one selected from the group consisting of nitrile rubber, hydrogenated nitrile rubber, carboxyl-modified nitrile rubber and carboxyl-modified hydrogenated nitrile rubber.
The rubber reinforcing cord according to claim 1 or 2. The cross-linking agent comprises at least one selected from the group consisting of maleimide-based cross-linking agents and polyisocyanates.
The rubber reinforcing cord according to any one of claims 1 to 3. The first coating is free of resorcin-formaldehyde condensate.
The rubber reinforcing cord according to any one of claims 1 to 4. The mass of the first coating is in the range of 5 to 35% of the mass of the filament bundle.
The rubber reinforcing cord according to any one of claims 1 to 5. The content of the liquid component in the rubber reinforcing cord is in the range of 0.2 to 1.5% by mass.
The rubber reinforcing cord according to any one of claims 1 to 6. The content of the liquid component in the rubber reinforcing cord is in the range of 0.3 to 1.3% by mass.
The rubber reinforcing cord according to claim 7. A rubber product reinforced with the rubber reinforcing cord according to any one of claims 1 to 8. A rubber belt including a rubber matrix and the rubber reinforcing cord embedded in the rubber matrix.
The rubber product according to claim 9.

Images