JPWO2017183660A1 - Rubber reinforcing cord and rubber product using the same - Google Patents

Abstract

The rubber reinforcing cord of the present invention is a rubber reinforcing cord for reinforcing a rubber product, and includes at least one strand. The strand includes at least one filament bundle and a first coating provided so as to cover at least part of the surface of the filament bundle. The filament bundle consists essentially of polyparaphenylene terephthalamide fiber filaments. The first coating includes a rubber component and a crosslinking agent. The rubber reinforcing cord further includes a liquid component, and the content ratio of the liquid component in the rubber reinforcing cord is in the range of 0.1 to 2.0% by mass.

Description

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

  2. Description of the Related Art Rubber reinforcing cords formed using tough fibers are widely used as reinforcing materials for rubber products that repeatedly receive bending stresses such as rubber belts and tires. Since the rubber reinforcing cord is used as a tensile body for enhancing the dimensional stability of the rubber product, it requires a high tensile strength.

  The manufacturing process of the rubber reinforcing cord generally includes a process of applying a treatment agent containing resorcin, formaldehyde, rubber latex (RFL) to the fiber and drying it (RFL process process). Further, as the treating agent applied to the fiber, a treating agent containing a material that is crosslinked by heat treatment and not containing a resorcin-formaldehyde condensate may be used. With the coating formed by such a treatment agent, the rubber reinforcing cord can improve the adhesion 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 an aramid fiber. Aramid fibers are generally fibers having high strength and high elastic modulus, and are widely used as reinforcing cords for rubber belts for power transmission. For example, Patent Documents 1 to 3 propose rubber reinforcing cords obtained by processing aramid fibers using a treatment agent containing RFL. Further, for example, Patent Document 4 proposes a rubber reinforcing cord obtained by treating an aramid fiber with a treating agent that contains a material that is crosslinked by heat treatment and does not contain a resorcin-formaldehyde condensate.

JP-A-8-100300 Special table 2005-517097 gazette JP 2010-95814 A Japanese Patent No. 4217058

  However, among the aramid fibers, polyparaphenylene terephthalamide fibers known as para-type aramid fibers have a problem that the tensile strength is greatly reduced by heat treatment when the treatment agent is dried. In particular, the tensile strength is greatly reduced by heating during the RFL treatment process. On the other hand, in order to obtain good adhesion strength between the rubber reinforcing cord and the matrix rubber, it is necessary to give a sufficient amount of heat for the RFL reaction in the heat treatment during the RFL treatment process. Therefore, if the amount of heat applied during the RFL treatment process is suppressed to a low level, the decrease in tensile strength can be suppressed to a small level, but this causes a problem that sufficient adhesive strength between the matrix rubber and the rubber reinforcing cord cannot be obtained. In the case of using a treatment agent that contains a material that is crosslinked by heat treatment and does not contain a resorcinol-formaldehyde condensate, the amount of heat applied may be reduced compared with the case of using a treatment agent that contains RFL, but it is still a matrix rubber. When a heat amount necessary for obtaining a sufficient adhesive strength between the rubber reinforcing cord and the rubber reinforcing cord is applied, a decrease in tensile strength is inevitable. Thus, it has been difficult to obtain a rubber reinforcing cord having both high tensile strength and high adhesive strength using polyparaphenylene terephthalamide fiber.

  Accordingly, one of the objects of the present invention is to obtain a rubber reinforcing cord that includes polyparaphenylene terephthalamide fiber as a reinforcing fiber and that has both high tensile strength and high adhesive strength. Further, another object of the present invention is to provide a high strength rubber reinforced by such a rubber reinforcing cord and having a high tensile strength and a high adhesive strength between the matrix rubber and the rubber reinforcing cord. Is to provide products.

  As a result of intensive research, the present inventor used polyparaphenylene terephthalamide fiber as a reinforcing fiber, and in the case of a rubber reinforcing cord obtained by forming a film using a treating agent on the surface of the fiber, The ratio of the liquid components remaining in the cord (such as the solvent of the processing agent and moisture 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. The present invention has led to the following rubber reinforcing cords of the present invention that can be located and have 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 includes at least one strand,
The strand includes at least one filament bundle, and a first coating provided to cover at least a part of the surface of the filament bundle,
Contains
The filament bundle consists essentially of polyparaphenylene terephthalamide fiber filaments,
The first coating includes a rubber component and a crosslinking agent,
The rubber reinforcing cord further includes a liquid component, and the content ratio 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 polyparaphenylene terephthalamide fiber is used as a reinforcing fiber, a cord for rubber reinforcement that achieves both high tensile strength and high adhesive strength with matrix rubber is provided. it can. In addition, since the rubber product of the present invention is reinforced with such a rubber reinforcing cord, it is possible to realize a high tensile strength and a high adhesive strength between the matrix rubber and the rubber reinforcing cord.

It is a partial exploded perspective view showing typically an example of the rubber product of the present 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 includes at least one strand. The strand includes at least one filament bundle and a first coating provided so as to cover at least a part of the surface of the filament bundle. The filament bundle consists essentially of polyparaphenylene terephthalamide fiber filaments. The first coating contains a rubber component and a crosslinking agent. The rubber reinforcing cord of the present embodiment further includes a liquid component, and the content ratio 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 an aqueous treatment agent (first aqueous treatment agent for coating) used for producing the first coating, or moisture contained in the filament itself. It is constituted by the remaining.

  Hereinafter, the manufacturing method of the reinforcing cord of this 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 described above, the filament bundle consists essentially of polyparaphenylene terephthalamide fiber filaments. Here, “the filament bundle is substantially composed of polyparaphenylene terephthalamide fiber filament” means that the filament bundle includes filaments other than the polyparaphenylene terephthalamide fiber filament to such an extent that the effect of the invention is not greatly affected. It means that it may be included. For example, the filament bundle may include filaments other than polyparaphenylene terephthalamide fiber filaments 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 reinforcing fiber of a rubber reinforcing cord can be used. The filament bundle may consist only of polyparaphenylene terephthalamide fibers.

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

  The surface of the polyparaphenylene terephthalamide fiber filament contained in the filament bundle is preferably subjected to pretreatment for increasing the adhesive strength. A preferred example of the 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 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 include Nagase ChemteX's Denacol series, DIC's Epicron series, and Mitsubishi Chemical's Epicoat series. Moreover, a polyurethane resin and an isocyanate compound can be similarly used as a pretreatment agent. 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. 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 film by pretreatment using such a treatment agent. Is further provided. By using a polyparaphenylene terephthalamide fiber filament whose surface is pretreated, it is possible to enhance the adhesion 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 plural. The filament bundle may be a bundle of a plurality of filament bundles. In this case, each of the plurality of filament bundles may be twisted or may not be twisted. Moreover, it may be twisted in a state where a plurality of filament bundles are combined, or may not be twisted.

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

  The first coating is formed by supplying a first aqueous coating agent for coating described later to at least a part of the surface of the filament bundle and drying it by heat treatment. The supply of the first aqueous treatment agent to the surface of the filament bundle may be performed by, for example, impregnating the filament bundle with the first aqueous treatment agent for coating, or at least part of the surface of the filament bundle with the first aqueous coating solution. It can be carried out by applying a treatment agent. In addition, the water | moisture content which filament itself has and the solvent (for example, water) of an aqueous processing agent are substantially removed by the heat processing in this case.

  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 may contain only one type of rubber as a rubber component, or may contain a plurality of types. These rubbers are preferable in that they are less swelled by oil and excellent in oil resistance. In the present specification, the term “nitrile rubber” means a nitrile rubber (acrylonitrile-butadiene copolymer rubber) that is not hydrogenated or carboxyl-modified unless otherwise specified. The iodine value of the 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 0-50.

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

  The first coating further contains a cross-linking agent. When the first coating contains a cross-linking agent, the rubber reinforcing cord of the present embodiment can improve the adhesion with the matrix rubber. Examples of crosslinking agents include quinonedioxime crosslinking agents such as P-quinonedioxime, methacrylate crosslinking agents such as lauryl methacrylate and methyl methacrylate, DAF (diallyl fumarate), DAP (diallyl phthalate), TAC (Triallyl cyanurate) and TAIC (triallyl isocyanurate) and other allyl crosslinking agents, bismaleimide, phenylmaleimide and maleimide crosslinking agents such as N, N′-m-phenylenedimaleimide, aromatic or aliphatic Organic diisocyanates, polyisocyanates, blocked isocyanates, blocked polyisocyanates, aromatic nitroso compounds, sulfur, and peroxides are included. These crosslinking agents may be used alone or in combination of two or more. These crosslinking agents are selected in consideration of the type of rubber contained in the first coating, the type of matrix rubber in which the rubber reinforcing cord is embedded, and the like. In addition, it is preferable that these crosslinking agents are used in the form of an aqueous dispersion so that the crosslinking agent is present uniformly in the aqueous treatment agent for producing the first coating film. The crosslinking agent may be at least one selected from the group consisting of a maleimide crosslinking agent, an organic diisocyanate, and an aromatic nitroso compound.

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

  The first coating may further contain a filler. Examples of fillers include fine particles of covalently bonded compounds such as carbon black and silica, fine particles of hardly soluble salts, fine particles of metal oxide, fine particles of metal hydroxide, fine particles of complex 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 diameter 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 diameter is a value obtained by measuring the particle diameter of 50 or more particles using a transmission electron microscope and dividing the total of the particle diameters 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.

  When the filler is dispersed in the rubber, it has an effect of improving properties such as the tensile strength and tear strength of the coating. In addition to these effects, the filler also has the effect of improving the adhesive strength by increasing the cohesive strength of the adhesive component between the fiber and the coating and between the coating and the matrix rubber. These effects are greatly influenced by the particle size and blending amount of the filler.

  It is preferable that a 1st film does not contain a resorcinol-formaldehyde condensate. In that case, when producing the first coating, it is not necessary to use a substance with a large environmental load such as formaldehyde and ammonia, so that no environmental measures are required for the operator. However, the first coating film may contain a resorcin-formaldehyde condensate.

  In addition to the rubber component and the crosslinking agent, the first coating film further includes a filler and further other components (for example, a metal oxide other than the metal oxide added as the filler or a resin). May be.

  The contents of the rubber component and the crosslinking agent in the first coating are not particularly limited. The content rate of the rubber component in the first coating can be, for example, 50 to 90% by mass. Moreover, the content rate of the crosslinking agent in a 1st film can be in the range of 10-50 mass%, for example.

  The mass of the first coating provided on at least the surface of the filament bundle is not particularly limited and may be adjusted as appropriate, but it is preferably provided so as to be within a range of 5 to 35% of the mass of the filament bundle. The mass of the first coating may be in the range of 10 to 25% of the mass of the filament bundle, or may be in the range of 12 to 20% by mass. When the mass of the first coating is too large, problems such as a decrease in the 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, when the mass of the first coating is too small, the strands are likely to fray or the function of protecting the fibers by the first coating is reduced, and as a result, the life of the rubber product may be reduced. .

  In order to improve the adhesion to the matrix rubber, the rubber reinforcing cord of the present embodiment may further include a second film formed on the first film. The treatment agent for forming the second coating may be the same as or different from the first aqueous treatment agent for coating. For example, you may form a 2nd film with a processing agent in which a component and a solvent differ from the aqueous processing agent for 1st films. In order to further improve the adhesion to the matrix rubber, it is possible to provide a further coating on the second coating.

  The number of twists of the rubber reinforcing cord of the present embodiment is not particularly limited. The number of twists added to one strand (hereinafter, sometimes referred to as a lower twist) is, for example, in the range of 20 to 160 times / m, in the range of 30 to 120 times / m, or in the range of 40 to 100 times / m. It may be a range. Furthermore, the number of twists (hereinafter sometimes referred to as upper twists) applied to a plurality of strands is also in the range of, for example, 20 to 160 times / m, 30 to 120 times / m, or 40 to 100. It may be in the range of times / m. The Lang twist may be the same as the lower twist direction and the upper twist direction, and the Moro twist may be the reverse of the lower twist direction and the upper twist direction. There is no limitation in the direction of twist, and it may be the S direction or the Z direction.

  The content rate 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, this liquid component is a residual solvent such as a solvent (for example, water) contained in an aqueous treatment agent used when a film is formed or moisture contained in the filament itself. In the rubber reinforcing cord of the present embodiment, in the heat treatment when the first coating is produced, the second coating is produced when the rubber reinforcing cord of the present embodiment further includes the second coating. In the heat treatment, the polyparaphenylene terephthalamide fiber is pulled 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. The content of the liquid component is less than 0.1% by mass, that is, the heat treatment at the time of producing the first film, and further the heat treatment at the time of producing the second film are contained in the solvent of the treatment agent for producing the film and the fiber. When it is carried out so that almost all the water is removed, the tensile strength of the polyparaphenylene terephthalamide fiber is lowered, and as a result, the tensile strength of the rubber reinforcing cord is lowered. On the other hand, when the content of the liquid component exceeds 2.0% by mass, a sufficient amount of heat has not been applied to the coating so that sufficient adhesive strength with the matrix rubber can be realized. It is not possible to obtain a rubber reinforcing cord capable of realizing 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, More preferably, the content is 3 to 1.3% by mass.

  Here, the “content ratio of the liquid component in the rubber reinforcing cord” specified in the present invention is a value obtained as follows. A 5 m long cord is taken as a sample from the rubber reinforcing cord, the sample is measured with an electronic balance, and this value is taken 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, and after being placed in a desiccator for 30 minutes, the value measured with an electronic balance was defined as mass B, and the difference between mass A and mass B Was the mass (AB) of the liquid component contained in the cord. The percentage ({(A−B) / A} × 100) of the mass (A−B) of the liquid component contained in the cord with respect to the mass A of the cord is defined as the content (%) 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 it is, an appropriate heating temperature and heating time may be set so that the solvent can be completely removed.

  When the rubber reinforcing cord further includes a second coating provided on the first coating, heat treatment is also performed when the second coating is produced. Therefore, it is preferable that the heat treatment for producing the second coating is also performed within a range that prevents a decrease in tensile strength and adhesive strength. In this case, the second coating is applied to the liquid component in the rubber reinforcing cord. In some cases, a liquid such as a remaining solvent is contained. Therefore, in the case of the rubber reinforcing cord including the second coating, it is preferable that the content of the liquid component in the rubber reinforcing cord is in the range of 0.5 to 2.0 mass%.

[Method of manufacturing rubber reinforcing cord]
An example of a method for manufacturing the rubber reinforcing cord of this embodiment will be described below. In addition, since the matter demonstrated about the rubber | gum reinforcement cord of this embodiment is applicable to the following manufacturing methods, the overlapping description may be abbreviate | omitted. 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 filament bundle is produced by bundling a plurality of filaments, and further an aqueous treatment agent (first aqueous treatment agent for coating) used for the production of the first coating is prepared. Next, the first aqueous coating agent for coating is supplied to at least a part of the surface of the filament bundle. Thereafter, heat treatment is performed to remove the solvent in the first aqueous coating agent. As a specific example, first, 1000 filaments are aligned to form one bundle, and the surface of the bundle is coated or impregnated with the first aqueous coating agent for coating. Thereafter, the solvent in the first aqueous coating agent for coating is removed by heat treatment. The filament bundle consists essentially of polyparaphenylene terephthalamide fiber filaments.

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

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

  The filament bundle on which the first film 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, description thereof will be omitted. In this way, the rubber reinforcing cord of this embodiment can be manufactured. Note that a plurality of bundles of filaments on which the first film is formed may be formed, and the plurality of bundles of filaments may be bundled to add an upper twist. The direction of the upper twist may be the same as or different from the direction of twist of the filament bundle (the direction of the lower twist). Alternatively, a plurality of filament bundles on which the first film is formed may be formed, and a twist may be added to a bundle of a plurality of filament bundles without giving a twist to each filament bundle.

  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 manufacturing method of the present embodiment, a rubber reinforcing cord is formed by applying or impregnating the first aqueous coating treatment agent to the filament bundle and then twisting the bundle in one direction.

  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 film may be formed by The type of the second coating can be appropriately selected according to the matrix rubber of the rubber product to which the rubber reinforcing cord is applied, and is particularly preferably selected from the viewpoint of improving adhesiveness.

  The conditions of the heat treatment for removing the solvent of the second coating treatment agent are not particularly limited, so that 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 appropriately adjust the treatment temperature and the treatment time.

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

  The first aqueous coating agent for coating may include 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 of these rubber latexes, or may contain a plurality of these rubber latexes.

  The first aqueous coating 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 these rubber latexes.

  The first aqueous coating agent for coating further contains a crosslinking agent. Since the crosslinking agent contained in the first aqueous coating agent for coating is the same as that described above as the crosslinking agent contained in the first coating, description thereof is omitted here. In addition, it is preferable to use a crosslinking agent in the form of an aqueous dispersion in order to make it exist uniformly in an aqueous processing agent.

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

  It is preferable that the first aqueous coating agent for coating does not contain resorcin-formaldehyde condensate. However, the first aqueous coating agent for coating may contain a resorcin-formaldehyde condensate.

  The first aqueous coating treatment agent may contain a filler and further other components in addition to the rubber latex and the crosslinking agent. For example, the first aqueous coating agent for coating may contain a resin, a plasticizer, an anti-aging 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 is no particular limitation on the rubber product. Examples of rubber products of the present embodiment include automobile and bicycle tires, transmission belts, and the like. Examples of the transmission belt include a meshing transmission belt and a friction transmission belt. Examples of the meshing transmission belt include a toothed belt represented by an automobile timing belt and the like. Examples of the friction transmission belt include a flat belt, a round belt, a V belt, a V-ribbed belt, 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 for 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 this embodiment is embedded in the rubber product (for example, rubber belt) of this 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, hydrogenated 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 hydrogenated nitrile rubber and hydrogenated nitrile rubber in which a zinc acrylate derivative is dispersed is preferable from the viewpoint of water resistance and oil resistance. The matrix rubber may further contain a carboxyl-modified hydrogenated nitrile rubber. In addition, it is preferable in terms of adhesiveness that the coating of the rubber reinforcing cord and the rubber composition of the rubber product contain the same type of rubber or be made of the same type of rubber.

  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 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 in 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 more specifically with reference to examples and comparative examples.

[Examples 1 to 10 and Comparative Examples 1 to 6]
<Manufacture of rubber reinforcing cord>
First, “Kevlar 29” (1670 dtex) manufactured by Toray DuPont, which was pretreated with a pretreatment agent containing an epoxy resin, was prepared. 1000 pieces of the “Kevlar 29” were converged and used as a filament bundle. After immersing this filament bundle in the first aqueous coating agent for coating having the composition shown in Table 1 below, the solvent was evaporated by heat treatment at 200 ° C., and the “content ratio of liquid component” shown in Tables 3 and 4 The 1st film was formed so that it might become. Note that the solid content of the first aqueous coating agent for coating was 20% by mass, and the mass of the first coating was 20% of the mass of the filament bundle. The “liquid component content” was adjusted by changing the heat treatment time. The filament bundle with the first coating thus produced is twisted into a Z twist at a rate of 40 turns / m, and two of them are bundled and twisted into a Z twist at a rate of 100 turns / m. A rubber reinforcing cord was obtained. About the obtained rubber | gum reinforcement cord, the content rate, tensile strength, and adhesive strength of a liquid component were measured. The measuring method of the content rate of a liquid component, tensile strength, and adhesive strength is as follows.

<Content of liquid component>
Within 30 minutes after the heat treatment carried out after immersing the filament bundle in the first aqueous coating agent, a 5 m long cord was sampled from the resulting rubber reinforcing cord. The sample was measured with an electronic balance, and this value was defined as the mass A of the cord. Next, the sample was placed in a dryer heated to 150 ° C. for 30 minutes to remove the solvent in the sample, and after being placed in a desiccator for 30 minutes, the value measured with an electronic balance was defined 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 cord. The percentage ({(A−B) / A} × 100) of the mass (A−B) of the liquid component contained in the cord with respect to the mass A of the cord was determined and used as the content (%) of the liquid component. Tables 3 and 4 show the liquid component content of the rubber reinforcing cords of Examples 1 to 10 and Comparative Examples 1 to 6.

<Tensile strength>
For the rubber reinforcing cords of each example and comparative example, a tensile test was performed using a commonly used tensile tester and a commonly used cord grip, and the breaking strength obtained at that time was determined as the tensile strength. It was. The breaking strength was measured according to ASTM 7269. The unit is N / code. Tables 3 and 4 show the tensile strengths of the rubber reinforcing cords of Examples 1 to 10 and Comparative Examples 1 to 6.

<Adhesive strength>
A canvas, a rubber reinforcing cord, and a matrix rubber sheet were stacked in this order, and pressed at 160 ° C. for 30 minutes to prepare a test piece for an adhesive strength test. 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, a material mainly composed of hydrogenated nitrile rubber having the composition shown in Table 2 was used. Next, the cord and the matrix rubber were each gripped, one was fixed, the other was peeled off in the length direction of the rubber reinforcing cord, and the strength per 25 mm width was measured.

  The liquid component content 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, since the solvent in the first film and the moisture in the filament were completely removed by the heat treatment, the liquid component content was less than 0.1% by mass. . 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 was subjected to an excessive heat treatment exceeding the range of the heat treatment assumed for obtaining the rubber reinforcing cord of the present invention. The rubber reinforcing cord was subjected to an insufficient heat treatment less than the range of heat treatment envisaged for obtaining 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 tensile strength or 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, the peeling interface was partially damaged by rubber, and when it was less than 150 N / 25 mm, the interface was in the vicinity of the first coating. From this result, it was confirmed that the ratio of the liquid component remaining in the cord after the formation of the first coating (mainly the solvent for the first aqueous coating agent) has a correlation with the tensile strength and the adhesive strength. It was.

[Examples 11 to 20 and Comparative Examples 7 to 11]
<Manufacture of rubber reinforcing cord>
First, in the same manner as in Examples 1 to 10 and Comparative Examples 2 to 6, a first coat is formed on the surface of the filament bundle, and the filament bundle with the first coat is Z-twisted at a rate of 40 times / m. A cord was obtained by twisting the bottom and bundling two of them and twisting them into a Z twist at a rate of 100 turns / m. Next, a second coating agent having the composition shown in Table 5 below was applied onto the cord after twisting and dried to form a second coating. The rubber reinforcing cords obtained by forming the second coating on the cords after the first twist produced in the same manner as in Examples 1 to 10 and Comparative Examples 2 to 6, respectively, were compared with Examples 11 to 20 and Comparatives, respectively. The rubber reinforcing cords of Examples 7 to 11 were used. In Examples 11 to 20 and Comparative Examples 7 to 11, the second coating was 10% by mass with respect to the cord after the first twist. The drying of the second coating treatment agent was performed at a treatment temperature of 100 ° C. and a treatment time of 2 minutes. The content of the liquid component after forming the second coating is in the range of 0.5 to 1.9% by mass as shown in Table 6, and the second coating treatment is applied to the liquid component of the rubber reinforcing cord. It is thought that the solvent of the agent is also included. About the obtained rubber | gum reinforcement cord, the content rate, tensile strength, and adhesive strength of a liquid component were measured. The measuring method of the content rate of a liquid component, tensile strength, and adhesive strength is the same as Examples 1-20 and Comparative Examples 1-6. However, the content rate of the liquid component was measured within 30 minutes after the heat treatment after applying the second coating agent. These results are shown in Tables 6 and 7. Tables 6 and 7 also show the liquid component content measured within 30 minutes after the heat treatment when the first film is formed and before the second film is formed.

  In the rubber reinforcing cords of Examples 11 to 20, the content ratio of the liquid component after the formation of the second coating satisfied the range of 0.5 to 2.0% by mass. In the rubber reinforcing cords of Comparative Examples 7 to 11, the liquid component content exceeded 2% by mass. In other words, the rubber reinforcing cords of Comparative Examples 7 to 11 were subjected to insufficient heat treatment that did not satisfy the range of heat treatment envisaged 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 for improving the adhesion 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 in the vicinity of the first coating. That is, it was confirmed that the ratio of the liquid component contained in the rubber reinforcing cord has a correlation with the tensile strength and the adhesive strength even in the rubber reinforcing cord provided with a plurality of layers of the coating.

  The cord for reinforcing rubber according to the present invention can realize high adhesive strength with a matrix rubber and high tensile strength, and therefore can be applied to reinforcement of various rubber products. For example, it can be suitably used as a reinforcing cord for a timing belt or the like that requires a high level of heat resistance and bending fatigue resistance. Moreover, since the rubber product of this invention can endure a high load, it is applicable to various uses.

Claims (10)

A rubber reinforcing cord for reinforcing a rubber product,
The rubber reinforcing cord includes at least one strand,
The strand includes at least one filament bundle, and a first coating provided to cover at least a part of the surface of the filament bundle,
Contains
The filament bundle consists essentially of polyparaphenylene terephthalamide fiber filaments,
The first coating includes a rubber component and a crosslinking agent,
The rubber reinforcing cord further includes 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 mass%.
Cord for rubber reinforcement. 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 mass%.
The rubber reinforcing cord according to claim 1. The rubber component includes 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 includes at least one selected from the group consisting of maleimide cross-linking agents and polyisocyanates,
The rubber reinforcing cord according to any one of claims 1 to 3. The first coating does not contain 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 cord for rubber reinforcement according to any one of claims 1 to 5. A resin layer provided between the filament bundle and the first coating;
The rubber reinforcing cord according to any one of claims 1 to 6. The resin layer contains at least one selected from the group consisting of an epoxy resin, a polyurethane resin, and an isocyanate compound,
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 comprising a rubber matrix and the rubber reinforcing cord embedded in the rubber matrix.
The rubber product according to claim 9.

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