JP6799381B2 - Carbon fiber cord for rubber reinforcement - Google Patents

Description

The present invention relates to a carbon fiber cord for rubber reinforcement, and more particularly to a carbon fiber cord for rubber reinforcement which is most suitable for belt reinforcement.

In recent years, carbon fibers having excellent properties such as high elastic modulus, high strength, dimensional stability, heat resistance and chemical resistance are expected as rubber reinforcing fibers for applications such as tires, hoses and belts by taking advantage of these properties. Has been done. In particular, in various belts such as toothed belts, carbon fibers having high elastic modulus characteristics are expected to bear a high load even when the elongation is in the range of 0.1 to 0.3%.
However, the surface of carbon fiber is often relatively inactive, and as it is, the adhesiveness to a matrix such as rubber or resin is insufficient, and the characteristics of carbon fiber cannot be fully exhibited. was there.

Therefore, various methods for treating the surface of carbon fibers have been proposed so far under the same conditions as the treatment methods for other various rubber reinforcing fibers, for example, organic fibers such as polyester. For example, Patent Document 1 discloses a method in which untwisted carbon fibers are treated with a resorcin-formalin-rubber latex (RFL) -based adhesive, then twisted, and then further bonded. However, a method of increasing the impregnation property of the treatment liquid by passing the fiber through the treatment liquid before twisting is one of the general-purpose methods as a conventional treatment method of inorganic fibers such as glass fiber. However, in the process of twisting the yarn after the treatment, there is a problem that the resin portion interposed between the single yarns is destroyed and the adhesive film becomes weak. Further, Patent Document 2 discloses a method of pretreating a carbon fiber bundle with a flexible treatment liquid containing a urethane resin as a main component. However, such treatment results in soft treatment coatings and cords, and as a result, it is unsatisfactory as a treatment method for carbon fibers, which is rigid in the first place as compared with organic fibers.

Japanese Unexamined Patent Publication No. 2014-070296 Japanese Unexamined Patent Publication No. 2011-241502

An object of the present invention is to provide a carbon fiber cord for rubber reinforcement having improved fraying property and bending fatigue property of the fiber cord on the cut surface of a rubber product.

The carbon fiber cord for rubber reinforcement of the present invention is a carbon fiber cord for rubber reinforcement in which a resin is adhered to the surface of the carbon fiber bundle, and resin C is present on the outermost surface layer of the carbon fiber cord for rubber reinforcement, and the resin. C is a polymer adhesive containing halogen, and resin C is carbon black.
And zinc oxide are contained, the distance between the outer fulcrums (edge span length) of the carbon fiber cord for rubber reinforcement is 25 mm, and the following three-point bending strength measured under the conditions of a test speed of 25 mm / min is 20 MPa or more. It is characterized by being.
3-point bending strength = bending load 8Lv / (π · D ³ )
[However, Lv: edge span length, D; cord gauge (cord diameter). ]
Further, the resin is composed of at least two types of layers, the resin A existing in the inner layer contains an epoxy compound and / or an isocyanate compound as a constituent component, and the resin B existing in the outer layer contains a rubber latex component as a constituent component of the resin A. solid content adhesion quantity is larger than the solid adhered amount of the resin B and, it is preferable that the fibers constituting the carbon Moto繊維束is twisted piece.

According to the present invention, there is provided a carbon fiber cord for rubber reinforcement having improved fraying property and bending fatigue property of the fiber cord on the cut surface of a rubber product.

The carbon fiber cord for rubber reinforcement of the present invention is a carbon fiber cord for rubber reinforcement in which resin is adhered to the surface of a carbon fiber bundle, and the bending strength measured by a three-point bending device is 20 MPa or more. Is. Further, the resin is composed of at least two types of layers, the resin A existing in the inner layer contains an epoxy compound and / or an isocyanate compound as a constituent component, and the resin B existing in the outer layer contains a rubber latex component as a constituent component, and the solid resin A is formed. It is preferable that the amount of the component adhered is larger than the amount of the solid content adhered to the resin B. Here, the bending strength measured by the three-point bending device of the present invention is the bending strength measured by the three-point bending device under the conditions of a distance between fulcrums of 25 mm and a test speed of 25 mm / min.

The most important requirement in the carbon fiber cord for rubber reinforcement of the present invention is that the bending strength measured by the three-point bending device is 20 MPa or more. This bending strength is improved by sufficiently focusing each single yarn in the carbon fiber bundle, and it becomes possible to obtain a cord of 20 MPa or more. That is, it is important that the resin penetrates sufficiently into the carbon fiber bundle, and in addition to the permeation, it is possible to crosslink between the single yarns constituting the carbon fiber bundle. preferable. In the case of cross-linking, when the carbon fiber cord is bent, the stress of each single yarn is not dispersed and the collective stress is generated. Therefore, the cord does not bend immediately, and it is possible to obtain sufficient bending strength. Furthermore, due to the penetration of the resin into the carbon fiber bundle, the initial flexural rigidity (elastic modulus) is slightly lower than when only the surface of the carbon fiber bundle is strongly focused, but the surface part is subjected to a fatigue test or the like. Even if the resin is slightly broken, the initial rigidity is maintained, it is difficult to bend, and it is possible to maintain sufficient bending strength. By the way, when only the surface of the carbon fiber cord is focused, for example, the fiber reinforced belt obtained as a final product may be cut along the fiber direction from the vicinity of the center of the cord fiber bundle in the manufacturing process. In that case, it leads to remarkable fraying. In the carbon fiber cord of the present invention, it is important that the resin exists inside the fiber bundle and the bending hardness is maintained.

Further, the carbon fiber cord for rubber reinforcement of the present invention has a three-point bending strength of 20 MPa or more. In the carbon fiber cord having such a sufficient bending strength, each single yarn is sufficiently focused by the resin. Since the wear caused by the friction between the single yarns is reduced, the dynamic fatigue such as bending fatigue is improved.

By the way, organic synthetic fibers such as polyester fibers and aromatic polyamide fibers (aramid fibers), which have been widely used for belt core wires, are compressed when the cord is hardened when the fiber bundle is restrained. When the load was concentrated on the part, a kink band was generated due to the slip of the crystal part of the polymer constituting the organic synthetic fiber, and a remarkable decrease in strength occurred. However, the carbon fiber used in the present invention has excellent compression characteristics as compared with such an organic synthetic fiber, and the generation of kink band due to the improvement in cord hardness is extremely unlikely to occur. The disadvantages of synthetic organic fibers due to the hardness of the cord do not apply to carbon fiber bundles.

Further, the resin sufficiently permeates the inside of the carbon fiber bundle of the present invention having such a hard three-point bending hardness. Then, even if it is cut along the direction of the fiber from the vicinity of the center of the cord fiber bundle in the manufacturing process of the fiber reinforced belt obtained as the final product, and even if it is cut anywhere in the belt manufacturing process, excellent fray resistance is obtained. It will be shown. In addition, since the characteristics inherent in each single yarn are expressed as a group, it exhibits excellent tensile strength and tensile elastic modulus. Further, the carbon fiber cord of the present invention having high bending strength is also excellent in bending rigidity (elastic modulus). In particular, when the carbon fiber cord of the present invention is used for a transmission belt application, the bending rigidity of the carbon fiber cord as the core wire greatly contributes to the axial bending rigidity of the entire belt, and the improvement of the axial bending rigidity is improved. , It will greatly contribute to the transmission performance of the belt such as slip test. If the bending strength is too large, that is, if the cord is too hard, but a higher rubber adhesive force is required and the balance with the rubber adhesive force is lost, it can be combined with the rubber used. However, it should be noted that the dynamic adhesive strength is insufficient and the expected effect tends not to be obtained. In that sense, the three-point bending hardness of the carbon fiber cord of the present invention is preferably 500 MPa or less, more preferably 20 to 350 MPa, and particularly preferably 50 to 350 MPa.

In such a carbon fiber cord for rubber reinforcement of the present invention, the resin is composed of at least two types of layers, the resin A existing in the inner layer is composed of an epoxy compound and / or an isocyanate compound, and the resin B existing in the outer layer. It is preferable that the rubber latex component is a constituent component and the amount of solid content attached to the resin A is larger than the amount of solid content attached to the resin B. It is preferable that the resin A is sufficiently impregnated inside the fiber bundle, and the resin B existing in the outer layer by being applied later is preferably present only outside the fiber bundle. Here, at least two kinds of layers are obtained by performing treatment of, for example, two or more baths, and the inner layer exists not only on the surface of the fiber bundle but also inside the fiber bundle. As described above, it is preferable that the material is sufficiently impregnated.

As the carbon fiber used in the carbon fiber cord for rubber reinforcement of the present invention, conventionally known carbon fibers can be used, but PAN-based carbon fibers having excellent strength are particularly preferable. Further, this carbon fiber needs to be a fiber bundle in which filaments are aggregated to form a bundle of threads, and because of the form of such a fiber bundle, it has excellent fatigue resistance for rubber reinforcement. It will be. The total fineness of this fiber bundle is preferably in the range of 500 dtex to 16000 dtex. More preferably, it is in the range of 4000 dtex to 16000 dtex. The number of filaments is preferably in the range of 1000 to 25000. It is preferably in the range of 25,000 to 25,000, and particularly preferably in the range of 3,000 to 24,000. The diameter of one fiber constituting the carbon fiber bundle is preferably in the range of 1 to 20 μm, particularly preferably 5 to 10 μm. The single yarn fineness is preferably in the range of 0.4 to 1.0 dtex.

Further, as the carbon fiber bundle used in the present invention, the modulus (elastic modulus) of the carbon fiber bundle is preferably 100 GPa or more, more preferably 230 GPa or more. The upper limit of the modulus of the carbon fiber bundle is 1000 GPa or less, and further, 400 GPa or less is a normal range. By increasing the modulus of the carbon fiber bundle, the fiber-reinforced rubber material reinforced with the carbon fiber cord for rubber reinforcement of the present invention becomes particularly excellent in dimensional stability. The strength of the carbon fiber bundle is preferably 2000 to 10000 MPa, more preferably 3000 to 6000 MPa, and the elongation at break is 0.2 to 3.0%. Is preferably 1.5 to 2.5%. Within such a range, fatigue resistance can be further improved. Further, the fiber may be pretreated with an epoxy resin, urethane resin or the like in advance at the silk reeling stage or after the silk reeling.

Further, the carbon fiber cord for rubber reinforcement of the present invention is preferably twisted. Further, it is preferable to twist the fiber bundle in the S direction or the Z direction (single twist). Furthermore, a plurality of single-twisted cords may be further aligned and twisted (multi-twisted) in the direction opposite to the single-twisted direction, but the multi-twisting of carbon fibers is from the viewpoint of process passability. Therefore, even when a plurality of fiber bundles are used, it is more preferable that the fiber bundles are aligned and twisted in the same direction. Here, the number of twists in the range satisfying the twist coefficient (TM) = 0.1 to 5.0 expressed by the following formula (1) maintains the permeability of the adhesive into the fiber cord and exhibits fray resistance. At the same time, it is preferable in terms of satisfying tensile properties and bending fatigue resistance, more preferably TM = 0.5 to 3.0, and further preferably 1.0 to 2.0.
TM = T × √D / 1150 (Formula 1)
[However, TM; twist coefficient, T; number of twists (times / m), D; total fineness (tex) are shown. ]

This formula is generally used for spun cotton yarn, and has a specific gravity of cotton for K = t / √N (K: twist coefficient, t: twist number t / inch, N: cotton count). Is converted to the specific gravity of carbon fiber, the cotton count is converted to fineness (tex), and recalculated. When the TM is close to 1.0, the single yarn is tilted by about 5.5 ° in the fiber axis direction to improve the alignment of the fiber bundles, so that the tensile strength is maximized. If the twist coefficient is further increased, the inclination of the single yarn becomes large, the single yarn is less likely to receive strain during bending, and the bending fatigue resistance is improved, but the tensile strength tends to decrease, and a small load is applied. The initial elongation at the time of receiving increases, and the hard-to-elongate property expected of the carbon fiber cord, in other words, the load that can be borne by the initial elongation such as 0.3% decreases.

By the way, it is preferable that the carbon fiber cord of the present invention is treated by immersing it in a treatment liquid containing a resin after twisting. In particular, it is preferable to treat the treatment liquid containing the resin B containing the rubber latex component arranged in the outer layer after twisting. If the twist coefficient for the fiber cord is too large, the penetration of the resin into the fiber bundle is hindered, and the fray resistance tends to deteriorate. In addition, when considering only immersion of the resin in the fiber bundle, if the resin is attached to the fiber bundle and then twisted, it becomes easier to penetrate into the fiber bundle, but in the subsequent twisting process, a single yarn is used. The resin interposed between the single yarn and the single yarn is broken and / or peeled off, and as a result, it tends not to sufficiently contribute to the improvement of bending fatigue resistance and the improvement of fray resistance due to wear reduction. In addition, when twisting is applied after the resin is attached, the fiber bundle is already restrained by the resin, so that not only the process passability is deteriorated, but also the alignment of each single yarn is deteriorated, and when a small load is applied. The initial elongation of the carbon fiber cord tends to increase, and the stretchable property expected of the carbon fiber cord, in other words, the load that can be borne by the initial elongation, tends to decrease.

In the carbon fiber cord of the present invention, it is preferable that at least two types of resins are formed by immersing the treatment liquid or the like. The resin A present in the inner layer preferably contains an epoxy compound and / or an isocyanate compound as a constituent component. Further, here, the inner layer is a concept including the inside of the fiber cord. The amount of solids attached to the resin A is preferably larger than the amount of solids attached to the resin B.

Here, as the resin A existing in the inner layer or the inside of the carbon fiber cord, those usually used as a sizing agent can be used. Resin A is impregnated inside the fiber bundle and intervenes between the single yarns of the carbon fiber to reduce damage due to wear when the carbon fiber cord moves, and the single yarn and the single yarn are separated by the resin A. By adhering, the fiber bundles are integrated, and in terms of tensile properties and the like, the performance of the original single yarn of carbon fibers can be exhibited as a fiber bundle.

In the present invention, it is preferable that the resin A is composed of an epoxy compound and / or an isocyanate compound. Such a resin A has a relatively low molecular weight and easily penetrates into the inside when the fiber body is immersed, and is self-condensed or crosslinked with other molecules by a subsequent heat treatment to bond the single yarns. Is possible. By using such a resin A, the resin A permeates into the fiber bundle, and the single yarn and the single yarn are adhered to each other in the fiber bundle, and it becomes easy to firmly bundle the single yarn.

Further, the resin A is preferably a resin having high toughness, preferably an isocyanate resin, a polyurethane resin, a urea resin, or a crosslinked product of isocyanate and epoxy. More specifically, it is preferably an isocyanate resin, a urea resin, or a crosslinked product of isocyanate and epoxy.

When an isocyanate resin is used as the resin A, for example, the method for applying the isocyanate compound is to immerse the fiber bundle in a solution prepared by dissolving the isocyanate compound in an organic solvent such as toluene, and then self-crosslink the isocyanate compound by heat treatment to obtain a fiber bundle. Examples thereof include a method of immersing a fiber bundle in an aqueous dispersion of an aqueous blocked isocyanate and then self-crosslinking an isocyanate compound in which the blocking agent is dissociated by heat treatment to obtain a fiber bundle. For workability, it is preferable to use an aqueous agent, and in the case of an aqueous agent, blocked isocyanate is preferably used. By using blocked isocyanate, water reacts with isocyanate only after the step of volatilizing water, so that it is possible to suppress the deactivation of functional groups in the previous dipping step or the like.

The isocyanate compound is preferably selected from aromatic diphenylmethane diisocyanate, toluene diisocyanate, aliphatic hexamethylene diisocyanate and the like. More preferably, it is recommended to use an aliphatic isocyanate having excellent permeability into the fiber bundle. More specifically, as the blocked isocyanate, dimethylpyrazole block, methylethylketone oxime block, and caprolactam block blocked isocyanate are preferable, and more specifically, dimethylpyrazole block hexamethylene diisocyanate is preferably used. Further, two or more of the above agents may be used in combination.
It is also preferable to use urea resin as the resin A. Here, the urea resin is a resin obtained by condensation of an amine and an isocyanate compound.

As a particularly preferable resin A in the present invention, a crosslinked product of an isocyanate compound and an epoxy compound can be mentioned. A fiber bundle can be obtained by infiltrating a relatively low molecular weight isocyanate compound and a highly reactive epoxy compound having a relatively low molecular weight into the fiber and then heat-treating the fiber. By cross-linking from the inside of the fiber bundle in this way, it becomes possible to bond the single yarn and the single yarn inside the fiber bundle and obtain a strongly bundled fiber bundle.

As the epoxy compound that can be used alone or in combination with an isocyanate compound, it is preferable that an epoxy compound having an epoxy group is attached to the fiber surface and the amount of the epoxy compound is increased by heat treatment or the like. , Reaction products of polyhydric alcohols such as ethylene glycol, glycerol, sorbitol, pentaerythritol, polyethylene glycol and halogen-containing epoxides such as epichlorohydrin, resorcin, pis (4-hydroxyphenyl) dimethylmethane, phenol / formaldehyde resin, A polyepoxide compound obtained by oxidizing an unsaturated compound with a reaction product of a polyhydric phenol such as resorcin / formaldehyde resin and the halogen-containing epoxide, or an unsaturated compound with peracetic acid or hydrogen peroxide, that is, 3,4-epoxycyclohexene epoxide. , 3,4-Epoxycyclohexylmethyl-3,4-epoxycyclohexene carboxylate, bis (3,4-epoxy-6-methyl-cyclohexylmethyl) adibate and the like.

Of these, a reaction product of a polyhydrin and epichlorohydrin, that is, a polyglycidyl ether compound of the polyhydrin is particularly preferable because it exhibits excellent performance. In particular, it is preferable to use an aqueous dispersion of an epoxy compound having a highly water-soluble sorbitol polyglycidyl ether structure. Further, it is particularly preferable to use an aqueous dispersion of a blocked isocyanate having an aliphatic hexamethylene diisocyanate (HDI) structure having excellent permeability into the fiber bundle and an epoxy compound having a highly water-soluble sorbitol polyglycidyl ether structure. preferable. More specifically, it is preferable to use dimethylpyrazole block hexamethylene diisocyanate or caprolactam block diphenylmethane diisocyanate as the blocked isocyanate, and to use a sorbitol polyglycidyl ether-based epoxy compound in combination as the epoxy compound.

Further, in order to obtain the fiber cord of the present invention, the resin A used as a sizing agent is attached to the inside of the fiber sizing body, and as a specific method thereof, a multifilament long fiber in which single fibers are gathered is attached. In addition, a method in which a plurality of fibers or tow-shaped long fibers are continuously sent from a bobbin or a beam creel and impregnated in a row containing a sizing agent. Examples thereof include a method of adhering by a roller touch method and a method of spraying and adhering the sizing agent by a spray method. Above all, in order to uniformly adhere the resin A to the fibers, a method of impregnating the fibers in a tank containing a sizing agent is preferable, and then it is preferable to adjust the adhesion amount to a certain level with a drawing roll.

Further, as described above, in order to impregnate and permeate the sizing agent into the fiber bundle more, a method of dispersing or dissolving the sizing agent in an aqueous marsion or an organic solvent and diluting it is preferable. At that time, when a treatment method of dissolving in an organic solvent is adopted, since a large amount of the organic solvent is used, the safety and work environment load are high, and the cost for the adhesive treatment equipment, the recovery / waste liquid treatment, and the peripheral equipment thereof is high. Is very high, so it is preferable to carry out an aqueous treatment as the method for carrying out the present invention. By the way, the organic solvent in which the sizing agent is dissolved tends to have high viscosity and insufficient penetration into the fiber bundle. From this point of view, a compound having a relatively low molecular weight and improved water solubility should be used. Is preferable.

When obtaining the carbon fiber cord of the present invention, the time for immersing the carbon fiber cord in the treatment solution containing the resin A is important for sufficient penetration of the sizing agent. The immersion time is preferably 3 seconds or longer, more preferably 10 seconds or longer. Immersion for a long time is not preferable from the viewpoint of productivity, and is preferably 60 seconds or less. Particularly preferably, it is 30 seconds or less. The tension of the yarn during immersion is also important for the sizing agent to sufficiently permeate. It is preferable to immerse the fibers with as low a tension as possible, but if the tension is too low, the single yarns constituting the fiber bundle and the single yarns will not be aligned well, and the tensile properties of the carbon fiber cord will eventually deteriorate. It is preferably carried out in the range of 0.01 to 0.5 cN / dtex. More preferably, it is carried out in the range of 0.03 to 0.2 cN / dtex. Further, it is preferable that the fiber bundle to which the sizing agent is applied is usually subjected to a heat treatment thereafter, and the dispersion medium of the sizing agent is dried and sometimes crosslinked by the heat treatment. The processing device is not particularly limited, and a contact type hot roller or the like can be used, but if a non-contact type hot air drying furnace is used, it is easy to work because there is no adhesion or dirt to the device due to the focusing agent. preferable. As a preferable heat treatment condition, a two-step heat treatment is preferable. Specifically, for example, it is preferable to perform drying at a temperature of 80 to 150 ° C. for 60 to 240 seconds, and then heat treatment at a temperature of 180 to 240 ° C. for 60 to 240 seconds.

In order to obtain the carbon fiber cord of the present invention, it is preferable to first dry the water content by the first-stage heat treatment while diffusing the treatment liquid containing the resin A on the surface of the cord and the inside of the cord into the inside of the fiber cord. If the treatment temperature is too high, volatilization of the water starts shortly after the water is distilled off, so that sufficient diffusion cannot be obtained, the focusing property becomes insufficient, and the cord tends to be soft. On the contrary, if the temperature is too low, the resin A, which is insufficiently dried, is transferred to the thread guide or the like, and the resin falls off from the cord, so that a sufficient amount of adhesion cannot be obtained. In the carbon fiber cord of the present invention, the resin B described later is present in the outer layer, but the resin A can be crosslinked to form a strong film by the second stage heat treatment following the dry heat treatment of the treatment liquid containing the resin A. , It is preferable to clearly divide the roles of the inner layer and the outer layer.

In the carbon fiber cord of the present invention, the amount of the resin A adhered is preferably 3.0 to 20% by weight. If the amount of adhesion is too small, the filaments of the fiber cord cannot be sufficiently focused, and the strength is reduced due to wear between the single yarns during bending fatigue, and the fraying property is reduced. On the other hand, if the amount is too large, there is a risk that the process passability such as gum-up in the bonding process will be lowered. More preferably, it is in the range of 5.0 to 15% by weight. The solid content can be controlled by squeezing with a pressure welding roller, scraping with a scrubber, blowing off with air, suction, or a beater. To increase the amount of solid, the immersion time can be increased. This may be done by increasing the concentration of the resin A solid content in the treatment liquid, dipping the resin A a plurality of times, or the like.

It is preferable that the treatment liquid containing the resin A is basically twisted and then the fiber cord is immersed in the treatment liquid for treatment. Further, in order to further impregnate the inside of the fiber cord of the resin A with the epoxy compound and / or the isocyanate compound, a treatment containing the same epoxy compound and / or the isocyanate compound as the resin A or different from the resin A before twisting is applied. It is also preferable to immerse it in a liquid and dry it. After that, it is also preferable to twist the untwisted pretreatment cord and treat it with the resin A again.

The carbon fiber cord for rubber reinforcement of the present invention requires that the resin B is present in the outer layer of the resin A existing in the inner layer, and the solid content of the resin A is larger than the solid content of the resin B. Is.
Then, as a method of applying such a resin B to the carbon fiber cord, as described above, after attaching a sizing agent made of the resin A to the fiber cord, the resin B having a rubber latex component as a constituent component is attached to the surface thereof. To attach. Further, as the composition of the resin B containing the rubber latex component as a constituent component, it is preferable to use resorcin formalin latex (RFL) from the viewpoint of adhesive strength, chemical resistance and the like.

Here, the resorcin / formalin / rubber latex (RFL) preferably contained in the carbon fiber cord of the present invention has a molar ratio of resorcin to formaldehyde in the range of 1: 0.6 to 1: 8. It is preferably used, and more preferably used in the range of 1: 0.8 to 1: 6. If the amount of formaldehyde added is too small, the crosslink density of the condensate of resorcin formalin decreases and the molecular weight decreases. Therefore, the adhesive layer cohesive force decreases, so that the adhesiveness decreases and the bending fatigue property decreases. In addition, if the amount of formaldehyde added is too large, the crosslink density increases and the resorcin-formalin condensate becomes hard, and the compatibility between RFL and rubber is hindered during co-smelting with the adherend rubber, resulting in adhesiveness. Tends to decrease. The mixing ratio of resorcin / formalin and rubber latex is preferably a solid content ratio of resorcin / formalin: rubber latex (RFL) in the range of 1: 3 to 1:16, particularly 1: 4 to 1:16. Those in the range of 1:10 are preferably used. If the ratio of rubber latex is too small, the co-vulcanization component with rubber is small and the adhesive strength tends to decrease. On the other hand, if the ratio of rubber latex is too large, sufficient strength cannot be obtained as an adhesive film. , Adhesive strength and durability tend to decrease, and the adhesiveness of the bonded fiber cord becomes significantly high, which may reduce process passability such as cam-up and handleability in the adhesive processing process and belt molding process. .. As the resorcin used, a pre-oligomerized resorcin-formalin initial condensate or a polynuclear chlorophenol-based resorcin-formalin initial condensate obtained by oligomerizing chlorophenol and resorcin with formalin is used alone or in combination as necessary. Is also good. Examples of the rubber latex used here include hydrogenated acrylonitrile-butadiene rubber latex, acrylonitrile-butadiene latex, isoprene rubber latex, urethane rubber latex, styrene-butadiene rubber latex, vinyl pyridine-styrene-butadiene rubber latex, and chloroprene rubber. There are latex, butadiene rubber latex, chlorosulfonated polyethylene latex, etc., and these are used alone or in combination. In particular, when the carbon fiber cord for rubber reinforcement of the present invention is used for hoses, belts, etc., hydrogenated acrylonitrile-butadiene rubber latex, acrylonitrile-butadiene latex, isoprene rubber latex, urethane rubber latex, chloroprene rubber latex, vinyl pyridine- It is preferably any one or more rubber latex selected from the group of styrene-butadiene rubber latex and chlorosulfonated polyethylene latex. Further, the latex is preferably of the same type as the matrix rubber of the fiber reinforced rubber material. For example, when hydride acrylonitrile-butadiene rubber is used as the matrix rubber, the latex type in the production method of the present invention is selected. , Hydrogenated acrylonitrile-butadiene rubber latex is preferably contained. The solid content weight ratio of the hydrogenated acrylonitrile butadiene rubber latex in the latex is preferably 50% by weight or more. If it is not the same type as the matrix rubber, it is preferable to use vinylpyridine-styrene-butadiene rubber latex or acrylonitrile-butadiene rubber.

Furthermore, when using the above-mentioned resorcin formalin latex (RFL), it is also preferable to use a cross-linking agent in combination. Examples of the cross-linking agent to be preferably added include amines, ethylene ureas, and blocked polyisocyanate compounds, but blocked polyisocyanate compounds are preferable in consideration of the stability of the treatment agent over time and the interaction with the pretreatment agent. Can be used. The addition rate of the cross-linking agent such as the blocked polyisocyanate compound is preferably in the range of 0.5 to 40% by weight, preferably 10 to 30% by weight, based on resorcin, formalin, and rubber latex (RFL). The adhesive strength is usually improved by increasing the addition amount, but conversely, if the addition amount is too large, the compatibility of the adhesive with the rubber tends to decrease, and the adhesive strength with the rubber tends to decrease.

Further, it is preferable that the resin C is present in the outermost outermost surface layer of the resin B existing in the outer layer containing the rubber latex component as a constituent component. The resin C is preferably a polymer-based adhesive containing chlorosulfonated polyethylene or halogen. The resin C preferably contains a rubber paste obtained by dissolving rubber in an organic solvent, a chlorosulfonated polyethylene, a halogen-containing polymer-based solvent-based adhesive, or a water-based adhesive, but is particularly water-based. It is preferable that it is a treatment agent for. Commercially available agents that can be used for such resin C include "Metallock F112" manufactured by Toyo Kagaku Kenkyusho Co., Ltd., "CHEMLOK CH233X", "CHEMLOK CH238S", and "CHEMLOK CH238S" manufactured by LORD. CHEMLOK CH8216 ”and the like. From the viewpoint of handleability, "CHEMLOK CH8216", which is a water-based adhesive and contains a halogen-containing polymer, carbon black, and zinc oxide, is particularly preferably used. These adhesives diffuse into the rubber of the adherend, improve the rigidity and cohesive force of the rubber matrix, and reduce the difference in rigidity from the carbon fiber cord, thereby further separating the carbon fiber cord and the rubber matrix. It is integrated to improve the adhesive strength. It is particularly effective when using a rubber matrix in which it is difficult to obtain sufficient adhesive strength between the carbon fiber cord and the rubber. It is preferable that the resin C is present not only on the outer side of the resin B as the outermost layer but also in the same layer mixed with the resin B.

In order to obtain the carbon fiber treatment cord for rubber reinforcement of the present invention, in order to attach the resin B and the resin C to the fibers following the resin A, contact with a roller, application by spraying from a nozzle, or a solution. It is preferable to adopt a means such as immersion in. The amount of the solid content of the resin B attached to the fiber cord is preferably 2.0% by weight or more, more preferably 2.0 to 6.0% by weight. Further, when the resin C is used, the amount of the solid content of the resin C attached to the fiber cord is preferably 3.0% by weight or more, more preferably 6 to 20% by weight, and particularly preferably in the range of 6 to 18% by weight. Further, it is preferably 12% by weight or less. It is preferable that the amount of resin C adhered is larger than that of resin B.

In order to control the amount of solids adhering to the fiber cord, it is possible to control the amount of solids adhering to the fiber cord by means of drawing with a pressure welding roller, scraping with a scrubber, blowing off with air blowing, suction, or a beater. In order to do so, it may be attached multiple times. As the treatment conditions, it is preferable to immerse the resin in a solution containing the resin B, and then dry and heat-treat at a temperature of 100 ° C. to 250 ° C. for 60 to 300 seconds. More preferably, it is dried in a temperature range of 100 to 180 ° C. for 60 to 240 seconds, and then heat-treated at a temperature of 200 to 245 ° C. for 60 to 240 seconds. If the drying / heat treatment temperature is too low, the adhesion to rubber tends to be insufficient, and if the drying / heat treatment temperature is too high, the RFL promotes air oxidation under high temperature and the adhesive activity decreases. It tends to end up. Further, it is preferable to perform drying and heat treatment at a temperature of 80 to 180 ° C. for 60 to 300 seconds after immersing in a solution containing the resin B. If the drying / heat treatment temperature is too low, the drying tends to be insufficient and the process passability tends to deteriorate. If the drying / heat treatment temperature is too high, the adhesive component is deactivated at a high temperature and the adhesive activity is lowered. It tends to end up.

The most preferable form of use is to attach 2.0 to 5.0% by weight of resin B, which is a composition containing resorcin, formalin, and rubber latex (RFL), and then contain a halogen-containing polymer, carbon black, and zinc oxide. It is preferable to use the water-based adhesive as the resin C and attach it in an amount of 3 to 20% by weight in terms of solid content.
Such a carbon fiber cord for rubber reinforcement of the present invention is a carbon fiber cord for rubber reinforcement with significantly improved fraying property, bending fatigue property, and initial elongation, and the carbon fiber cord for rubber reinforcement can be used as a reinforcing material. By using it, a carbon fiber reinforced rubber material having very excellent physical properties can be obtained.

In the carbon fiber reinforced rubber material containing the carbon fiber cord for rubber reinforcement of the present invention as a reinforcing material, the rubbers to be reinforced include acrylic rubber, acrylonitrile-butadiene rubber, hydride acrylonitrile-butadiene rubber, and isoprene rubber. , Urethane rubber, ethylene-propylene rubber, chloroprene rubber, silicone rubber, styrene-butadiene rubber, polysulfide rubber, natural rubber, butadiene rubber, fluororubber and the like. In particular, the production method of the present invention is most suitable for hydrogenated acrylonitrile-butadiene (H-NBR) rubber applications. In addition to the main component rubber, the above rubber includes inorganic fillers such as carbon black and silica, organic fillers such as kumaron resin and phenol resin, and softeners such as naphthenic oil for modifying the material. May be included.

Such a carbon fiber reinforced rubber material can be formed, for example, by arranging the required number of carbon fiber cords for rubber reinforcement, sandwiching them with rubber, and further pressurizing and heating with a press machine or the like. The obtained carbon fiber reinforced rubber material exhibits excellent durability against bending deformation and the like, and specific examples of the carbon fiber reinforced rubber material include belts and hoses.

Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited thereto. The evaluation in the examples of the present invention was carried out by the following measurement method.

(1) Cord weight (fineness), cord diameter (cord gauge), tensile strength, tensile elongation (cutting elongation), load at 0.3% elongation The measurement was performed according to JIS L1017. The load at 0.3% elongation was read from the resulting stress-strain curve.

(2) Flexural strength Measurement was performed with one cord according to the tire cord measuring method of ASTM D885 and Stiffness. The test piece length was 50 mm, the distance between the outer fulcrums (edge span length) was 25 mm, and the test speed for moving the fulcrum in the middle portion was 25 mm / min, using a three-point bending device. The stress was calculated by the following formula.
Flexural strength = bending load 8Lv / (π · D ³ ) (Formula 2)
[However, Lv: edge span length, D; cord gauge (cord diameter) is shown. ]

(3) Cord Peeling Adhesive Strength The carbon fiber cords for rubber reinforcement were arranged adjacent to each other with a width of about 30 mm, and evaluated by the adhesive strength when peeling from the rubber. As the evaluation rubber, H-NBR rubber prepared with the following composition was used and vulcanized by applying a press pressure of 1 MPa at a temperature of 180 ° C. for 30 minutes. In addition, the attachment of rubber to the peeled cord was evaluated.
(Mixed composition)
Hydrogenated acrylonitrile-butadiene rubber: 100 parts Carbon black: 50 parts Zinc oxide: 5 parts Plasticizer TOTM: 5 parts Stearic acid: 0.5 parts Antioxidant (Nowguard 445): 1.5 parts Anti-aging agent (Nocrack MBZ) ): 1 part silica: 8 parts

(4) Flexibility of cords Eight carbon fiber cords that have been subjected to adhesive treatment are embedded in two unvulcanized rubber sheets of hydrogenated acrylonitrile-butadiene rubber with a width of 50 mm, a length of 500 mm, and a thickness of 2 mm at equal intervals. Then, it was vulcanized at a temperature of 180 ° C. for 30 minutes at a press pressure of 1 MPa to obtain a belt-shaped rubber molded product. Next, the belt-shaped rubber molded product is attached to a roller having a diameter of 50 mm by applying a load of 30 kg, and is reciprocated at 100 rpm at a roller bending (contact) distance of 100 mm in an atmosphere of 100 ° C., and is repeatedly bent 100,000 times. After that, the cord was taken out and the residual strength was measured to determine the strength maintenance rate after bending fatigue.

(5) Fraying property In addition, the belt-shaped rubber molded body in which the carbon fiber cord of (4) was embedded was cut at an angle of 1 °, and the fiber cord exposed on the cross section of the cut portion at the center of the cord was focused. The state was visually observed and observed with an optical microscope to evaluate the fraying property. The fraying property was evaluated and judged in three stages as follows.
[Fraying property (after flexion fatigue test)]
◯: The filament of the fiber cord is focused, and no abnormality in appearance is observed, which is good.
Δ: Poor focusing is observed on some filaments of the fiber cord.
X: The filament of the fiber cord has a poor focusing and is not focused.

[Example 1]
55 g of a polyepoxide compound having a sorbitol polyglycidyl ether structure (Denacol EX-614B, manufactured by Nagase ChemteX, concentration 100%) and an aqueous solution of dialkyl sulfosuccinate sodium salt (Neocol SW-C, manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd., concentration) (70%) 15 g was added and stirred, and this was added to 353 g of water with stirring to dissolve it. To this, 228.0 g of a condensate of a dimethylpyrazole block-HDI trimmer having 3 or more functional groups (Trixene BI201, manufactured by Baxenden, UK, concentration 40%) was added with stirring to prepare an aqueous dispersion of resin A.
19.8 g of a resorcin-formalin initial condensate (Sumicanol 700S, manufactured by Sumitomo Chemical, concentration 65%) having a molar ratio of resorcin / formalin (R / F) of 1 / 0.6 was added to 154.5 g of water with 10% caustic soda. Dissolve in an alkaline aqueous solution containing 5.0 g of water and 19.9 g of 20% aqueous ammonia, and add 415 g of acrylonitrile-butadiene rubber latex (NIPOL LX1562, manufactured by Nippon Zeon Co., Ltd., concentration 41%) and 368.9 g of water. did. To this solution, 16.8 g of 37% formalin water was added and aged at 20 ° C. for 48 hours to prepare an aqueous dispersion of resin B containing an RFL-based adhesive treatment agent having a solid content concentration of 19.4%.

A carbon fiber twisted cord was obtained by performing single twisting in the Z direction with a twist number of 60 times / m using one carbon fiber (UTS50, manufactured by Toho Tenax) of 8000 dtex / 12000 filament. This fiber cord was fed at a speed of 5 m / min using a computer processor (CA Ritzler dip cord processor), immersed in the above resin A aqueous dispersion for 6 seconds, and then at a constant length of 120 ° C. Drying for 120 seconds, then heat treatment at a constant length of 235 ° C. for 60 seconds, followed by immersion in the aqueous dispersion of resin B containing the RFL-based adhesive treatment agent, and then drying at a constant length of 160 ° C. for 120 seconds. Then, it is heat-treated at 230 ° C. for 150 seconds, and further immersed in an aqueous dispersion (CHEMLOK CH8216, manufactured by LOAD, USA) containing a halogen-containing polymer, carbon black and zinc oxide and having a solid content of 30%, and then having a constant length. The mixture was dried at 150 ° C. for 120 seconds to obtain a carbon fiber cord. The carbon fiber cord contains 8.0% by weight of resin A containing an epoxy compound and an isocyanate compound as constituents in terms of solid content with respect to the carbon fiber twisted yarn cord, and resin B containing an RFL-based adhesive treatment agent. 5% by weight, 8.5% of resin C, which is an adhesive containing a halogen-containing polymer, carbon black, and zinc oxide, was attached. The production conditions and performance evaluation results of the obtained carbon fiber cord are summarized in Tables 1 and 2.

[Examples 2 to 4, Comparative Examples 1 to 3]
The carbon fiber cord was bonded in the same manner as in Example 1 except that the plying conditions and the treatment conditions for the aqueous resin A dispersion were changed as shown in Table 1. The manufacturing conditions and performance evaluation results of the obtained carbon fiber treatment cord are summarized in Tables 1 and 2.

[Example 5]
As the composition of the resin A aqueous dispersion, instead of the condensate of dimethylpyrazole block-HDI trimmer (“BI201”), ε-caprolactam block-diphenylmethane diisocyanate (MDI) (DM3031, manufactured by Meisei Chemical Works, Ltd., concentration 40). %) Was used, and the carbon fiber cord was bonded in the same manner as in Example 1. Tables 1 and 3 show the production conditions and performance evaluation results of the obtained carbon fiber cord.

[Example 6]
After the RFL-based adhesive treatment of the resin B, the carbon fiber cord was bonded in the same manner as in Example 1 except that the adhesive containing the halogen-containing polymer, carbon black and zinc oxide was not treated. Tables 1 and 3 show the production conditions and performance evaluation results of the obtained carbon fiber cord.

[Comparative Example 4]
Table 1 shows the production conditions and performance evaluation results of the carbon fiber cords in the same manner as in Example 1 except that an RFL-based adhesive treatment agent having a solid content concentration of resin B of 19.4% was used instead of the aqueous dispersion of resin A. And shown in Table 3.

In Examples 1 to 6 of the present invention, the bending strength was high, the bending fatigue property was excellent, and the fray resistance was also good as compared with the comparative examples.

According to the present invention, it is possible to provide a carbon fiber cord which is significantly improved in fraying property, has excellent adhesiveness to rubber, bending fatigue, and durability, and is suitably used as a core wire of a transmission belt. Although it is a fiber, it has good fraying property and bending fatigue property, and can be suitably used as a core wire of a friction transmission belt or a toothed belt.

Claims (4)

A carbon fiber cord for rubber reinforcement in which a resin is adhered to the surface of a carbon fiber bundle, and a polymer adhesive in which resin C is present in the outermost surface layer of the carbon fiber cord for rubber reinforcement and the resin C contains halogen. The following 3 was measured under the conditions that the resin C contained carbon black and zinc oxide, the distance between the outer fulcrums (edge span length) of the carbon fiber cord for rubber reinforcement was 25 mm, and the test speed was 25 mm / min. A carbon fiber cord for rubber reinforcement, characterized in that the point bending strength is 20 MPa or more.
3-point bending strength = bending load 8Lv / (π · D ³ )
[However, Lv: edge span length, D; cord gauge (cord diameter). ] The resin is composed of at least two types of layers, the resin A existing in the inner layer contains an epoxy compound and / or an isocyanate compound as a constituent component, and the resin B existing in the outer layer contains a rubber latex component as a constituent component, and the solid content of the resin A adheres. The carbon fiber cord for rubber reinforcement according to claim 1, wherein the amount is larger than the amount of solid content attached to the resin B. The solid content of resin A is 3.0 to 20% by weight, the solid content of resin B is 2.0 to 6.0% by weight, and the solid content of resin C is larger than that of resin B. The carbon fiber cord for rubber reinforcement according to claim 2, which is 3.0 to 20% by weight . The carbon fiber cord for rubber reinforcement according to any one of claims 1 to 3, wherein the fibers constituting the carbon fiber bundle are unilaterally twisted.