JP6877155B2 - 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 having significantly improved rubber adhesiveness.

In recent years, in response to issues such as the destruction of the global environment and the depletion of petroleum resources, energy saving and energy substitution, including automobiles and electrical equipment, have attracted a great deal of attention. The need for compactness is rapidly increasing. Fiber-reinforced composite materials are widely used as an alternative to metal chains used to drive camshafts in internal combustion engines for automobiles.

Carbon fiber, which has excellent properties such as high elastic modulus, high strength, dimensional stability, heat resistance, and chemical resistance, is expected as a rubber reinforcing fiber for applications such as tires, hoses, and belts by taking advantage of these properties. There is. In particular, various rubber belts such as toothed belts are expected to have carbon fibers as core wires because of their high elastic modulus. However, the surface of carbon fiber is often relatively inactive, and as it is, the adhesiveness to a matrix such as rubber is insufficient, and the characteristics of carbon fiber cannot be fully exhibited. Further, hydrogenated nitrile rubber, which is often used for toothed belts and the like, which are expected to use carbon fibers, has few double bonds in the rubber, and it is particularly difficult to achieve sufficient adhesion.

So far, various methods have been proposed in which the surface of the fiber is treated with an epoxy compound, a urethane compound, a resorcin, formalin, rubber latex (RFL) -based adhesive, etc. (Patent Documents 1-3), but the adhesive strength with rubber has been proposed. Has not been sufficiently improved.

Japanese Unexamined Patent Publication No. 2014-70296 Japanese Unexamined Patent Publication No. 2016-89294 Japanese Unexamined Patent Publication No. 2013-2002

The present invention relates to a carbon fiber cord for rubber reinforcement, and more particularly, to provide a carbon fiber cord for rubber reinforcement having significantly improved rubber adhesiveness.

The present invention is " a carbon fiber cord in which a resin is attached to the surface of a carbon fiber bundle, and the resin is a polymer component A having resorcin, formalin, and rubber latex as constituent components, and an outer layer of the polymer component A. The outermost layer of the carbon fiber cord is provided with a polymer component B composed of a nitrile rubber latex and / or a hydride nitrile rubber latex and a cross-linking agent, and the solid content of the polymer component A is 3 to 17% by weight, that of the polymer component B. Solid content is 13-37% by weight
A carbon fiber cord for rubber reinforcement, wherein the total solid content of the polymer component A and the polymer component B is 20 to 40% by weight. "I will provide a.

According to the present invention, a carbon fiber cord which is excellent in adhesiveness to rubber and is suitably used as a core wire of a toothed belt can be manufactured in consideration of the environment by a water-based adhesive treatment. For this reason, it becomes possible to efficiently manufacture high-performance fiber cords that can be applied to the core wires of toothed belts for automobiles and industries, which have been difficult to put into practical use in the past, and in terms of reducing environmental load and cost. It can be very effective.

The carbon fiber cord for rubber reinforcement of the present invention is a polymer component A containing resorcin, formalin rubber latex (RFL) as a constituent, and an outer layer of the polymer component A, and a nitrile rubber latex and / or the outermost layer of the cord. It is a rubber reinforcing carbon fiber cord characterized by the presence of a polymer component B containing a hydride nitrile rubber latex and a cross-linking agent as constituent components.

As the carbon fibers constituting the rubber reinforcing carbon fiber cord used in the present invention, conventionally known carbon fibers can be used, but PAN-based carbon fibers having excellent strength are particularly preferable. Further, it is preferably a fiber bundle for rubber reinforcement, and the total fineness 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 24000. More preferably, it is in the range of 3000 to 24000. The cross-sectional shape, physical characteristics of the fiber, microstructure, etc. of the fiber are not limited in any way. Further, the fiber may be pretreated with an epoxy resin, an isocyanate resin, a urethane resin, a resorcin, formalin, a rubber latex or the like which is the same as or different from the polymer component A in advance at the yarn-making stage or after the yarn-making.

As the polymer component A containing resorcin, formalin, and rubber latex as constituent components, those having a molar ratio of resorcin to formaldehyde in the range of 1: 0.6 to 1: 8 are preferably used, and more preferably 1: 1. It is used in the range of 0.8 to 1: 6. If the amount of formaldehyde added is too small, the crosslink density of the condensate of resorcin and 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. There is a fear. On the other hand, if the amount of formaldehyde added is too large, the resorcin-formalin condensate becomes hard due to the increase in the cross-linking density, and the compatibility between RFL and the rubber is hindered during co-vulcanization with the adherend rubber, and the adhesiveness tends to decrease. There is.

The mixing ratio of resorcin / formalin and rubber latex is preferably in the range of 1: 3 to 1:16 for resorcin / formalin: rubber latex in terms of solid content ratio, and in particular, 1: 4 to 1:10. Those in the range of 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 the rubber latex is too large, sufficient strength cannot be obtained as an adhesive film, so that the adhesive strength and durability tend to decrease, and the adhesiveness of the bonded fiber cord becomes remarkably high to adhere. In the processing process and the belt molding process, there is a risk that process passability such as cam-up and handleability may decrease.

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 nitrile rubber latex (hydrogenated acrylonitrile-butadiene rubber latex), nitrile rubber latex (acrylonitrile-butadiene rubber latex), isoprene rubber latex, urethane rubber latex, and styrene-butadiene rubber. There are latex, vinylpyridine-styrene-butadiene rubber latex, chloroprene rubber latex, butadiene rubber latex, chlorosulfonated polyethylene latex and the like, and these are used alone or in combination. In particular, the rubber reinforcing carbon fiber cord of the present invention preferably contains hydrogenated nitrile rubber latex and / or nitrile rubber latex. More preferably, hydrogenated nitrile rubber latex is preferable. Further, the hydrogenated nitrile rubber latex and / or the nitrile rubber latex may be modified by carboxyl modification or the like.

It is also preferable to use a cross-linking agent in combination with this resorcin formalin latex (RFL). Examples of the cross-linking agent to be preferably added include amines, ethylene ureas, maleimides, and isocyanate 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.

The polymer component B is an outer layer of the polymer component A and is treated on the outermost layer of the cord, and contains a nitrile rubber latex and / or a hydrogenated nitrile rubber latex, a cross-linking agent, carbon black, and zinc oxide as constituent components. It is preferable to do so. Nitrile rubber latex and / or hydrided nitrile rubber latex having a high affinity with the rubber component and a cross-linking agent component having a high affinity with the polymer component A are mixed, and their molecular chains are entangled to form adhesiveness and aggregation. It forms a highly effective cord film. Further, by adding carbon black or zinc oxide, the affinity with the rubber component can be further enhanced. More preferably, it contains a hydrogenated nitrile rubber latex, a cross-linking agent, carbon black and zinc oxide.
The polymer component B of these mixtures may be dissolved in an organic solvent and treated as a rubber paste, but from the viewpoint of handleability and the environment, it is preferable to disperse the polymer component B in water and treat it on the surface of the cord.

Examples of the cross-linking agent added to the polymer component B include amines, ethylene ureas, and blocked polyisocyanate compounds, which are blocked in consideration of the stability of the treatment agent over time and the interaction with the pretreatment agent. Polyisocyanate compounds can be preferably used. 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 aromatic diphenylmethane diisocyanate having excellent cross-linking performance. More specifically, as the blocked isocyanate, dimethylpyrazole block, methylethylketone oxime block, and caprolactam block blocked isocyanate are preferable, and more specifically, caprolactam block diphenylmethane diisocyanate is preferably used.

The polymer component B includes chlorinated natural rubber, polychloroprene, chlorinated polychloroprene, chlorinated polybutadiene, hexachloropentadiene, butadiene / hydride cyclic conjugated diene adduct, chlorinated butadiene styrene copolymer, and chlorinated ethylene propylene. Polymers and ethylene / propylene / non-conjugated diene ternary copolymers, chlorinated polyethylene, chlorosulfonated polyethylene, poly (2,3-dichloro-1,3-butadiene), brominated poly (2,3-dichloro- 1,3-butadiene), a copolymer of α-haloacrylonitrile and 2,3-dichloro-1,3-butadiene, chlorine-containing polymers such as chlorinated poly (vinyl chloride) and halogen-containing polymers such as bromine. Is even more preferable. These halogen-containing polymers diffuse into the rubber of the adherend while being entangled with the nitrile rubber latex and / or the hydride nitrile rubber latex, improving the rigidity and cohesive force of the rubber matrix, and the difference in rigidity from the carbon fiber cord. By reducing the amount of shavings, the carbon fiber cord and the rubber matrix are more integrated, and the adhesive strength is improved.

In a more preferable form, a polymer component A containing resorcin, formalin, and rubber latex as a constituent is attached in an amount of 3 to 17% by weight as a solid content, and then oxidized with nitrile rubber latex and / or hydride nitrile rubber latex, carbon black, and carbon black. It is preferable to attach the polymer component B containing zinc as a constituent component in an amount of 13 to 37% by weight as a solid content.
Further, in order to maintain the rubber adhesive force, the peeling adhesive force of the cord can be maintained by adhering the polymer component A and the polymer component B so that the total is 20 to 40% by weight.

In order to attach the polymer component A to the fiber, means such as contact with a roller, application by spraying from a nozzle, or immersion in a solution can be adopted. 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, and the amount of adhering is large. In order to do so, it may be attached multiple times.

When the dipping method is used, it is preferable to immerse the carbon fiber bundle in a solution containing the polymer component A, 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, after immersing in the solution containing the polymer component B, it is preferable to perform drying and heat treatment at a temperature of 80 to 180 ° C. for 60 to 300 seconds. 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.

Further, the carbon fiber cord used in the present invention is preferably a twisted carbon fiber. It is preferable that one or a plurality of the fibers are aligned and twisted (single twist) on one side in the S direction or the Z direction. A plurality of the above cords may be further aligned and twisted (multi-twisted) in the direction opposite to the one-sided twisting direction, but it is difficult to twist the carbon fiber from the viewpoint of process passability. Single twist is more preferable.
Here, the number of twists is within the range satisfying the twist coefficient (TM) = 0.1 to 5.0 represented by the following equation (1), and the permeability of the adhesive to the inside of the fiber cord is maintained, and the tensile physical characteristics and bending fatigue resistance It is preferable in terms of satisfying the characteristics, more preferably TM = 0.5 to 3.0, and even more preferably 1.0 to 2.0.
[Number 1]
TM = T × √D / 1150
[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, K = t / √N (K: twist coefficient, t: twist number t / inch, N: cotton count). Is converted to the specific gravity of carbon fiber, and 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. Further increasing the twist coefficient increases the inclination of the single yarn, makes it difficult for the single yarn to receive strain during bending, and improves bending fatigue resistance, but the tensile strength tends to decrease, and a small load is applied. The initial elongation at the time of receiving will increase, and the difficult-to-extend properties expected of the carbon fiber cord will decrease.

The twist may be applied before or after the resin is attached to the fiber bundle. When the final application is an application in which the fraying of the cut surface at the time of belt cutting is a concern, it is preferable to attach the resin before twisting because the polymer component permeates the inside of the fiber bundle and the fraying at the time of cutting is reduced. .. On the other hand, if the amount of the resin adhered before twisting is large, the twisting after the twisting results in poor alignment of the single yarns, resulting in deterioration of properties such as tensile strength and tensile elastic modulus. Preferably, a method of treating with the polymer component A before twisting and then twisting and then treating the polymer component B, or before twisting, with an epoxy resin, an isocyanate resin, a urethane resin, and a polymer component A in advance. Pre-treat with a treatment agent having high affinity for each of the carbon fiber and the polymer component A, such as the same / or different isocyanate, formalin, and rubber latex, and impregnate the inside of the fiber bundle with a treatment agent for reducing fraying, and then twist. It is preferable to apply and then treat the polymer component A and the polymer component B.

The types of rubber to be reinforced with the carbon fiber cord for rubber reinforcement obtained by the production method of the present invention include acrylic rubber, nitrile rubber (acrylonitrile-butadiene rubber), and hydride nitrile rubber (hydrogenated acrylonitrile-butadiene rubber). , Isoprene rubber, urethane rubber, ethylene-propylene rubber, chloroprene rubber, silicone rubber, styrene-butadiene rubber, polysulfide rubber, natural rubber, butadiene rubber, fluorine rubber and the like. In particular, the production method of the present invention is most suitable for hydrogenated nitrile (H-NBR) rubber applications. In addition to the main component rubber, the above rubber is softened with inorganic fillers such as carbon black and silica, organic fillers such as kumaron resin and phenol resin, and naphthenic oil for modification of the material. Various additives such as various vulcanizing agents such as agents may be contained.

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 a toothed belt and the like.

Hereinafter, the present invention will be described with reference to examples. Such examples are for the purpose of explaining embodiments of the present invention, and 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) The weight (fineness) and tensile strength of the cord were measured according to JIS L1017. (2) The peeling adhesive strength of the cord was measured by the following method.
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 force 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 state of rubber adhesion to the peeled cord was observed.

[Composite 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 (Nauguard 445): 1.5 parts Antioxidant (Antioxidant (TOTM): 5 parts Nocrack MBZ): 1 part 1,3-bis [1- (tert-butylperoxy) -1-methylethyl] benzene: 8 parts

[Example 1]
19.8 g of a resorcin-formalin initial condensate (Sumicanol 700S, manufactured by Sumitomo Chemical Co., Ltd., concentration 65%) having a molar ratio of resorcin / formalin (R / F) of 1 / 0.6 was added to 10 of 154.5 g of water. Dissolve in an alkaline aqueous solution containing 5.0 g of% caustic soda water and 19.9 g of 20% ammonia water, and add 425 g of hydrogenated formalin rubber latex (Zetopol2230LX, manufactured by Nippon Zeon Co., Ltd., concentration 40%) and 358.9 g of water. Added. 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 polymer component A containing resorcin, formalin, and rubber latex having a solid content concentration of 19.4%. It was adjusted.

In addition, 200 g of hydride nitrile rubber latex (Zetopol2230LX, manufactured by Nippon Zeon Co., Ltd., concentration 40%), 125 g of chlorosulfonated polyethylene rubber latex (manufactured by Seporex CSM, manufactured by Sumitomo Seika Co., Ltd., concentration 30%) and ε caprolactam blocked diphenylmethane. 55 g of diisocyanate (DM3031, manufactured by Meisei Chemical Works, Ltd., concentration 54%), 10 g of zinc oxide, and 10 g of carbon black were added with 550 g of water to obtain a polymer component B aqueous dispersion having a solid content concentration of 20.0%.

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 Co., Ltd.) of 8000dtex / 12000 filaments. This fiber cord is immersed in an aqueous dispersion of the polymer component A containing the above-mentioned resorcin, formalin, and rubber latex as a constituent component using a compute treatment machine (CA Ritzler dip code processing machine), and then at 120 ° C. Drying was performed for 120 seconds, followed by heat treatment at 235 ° C. for 60 seconds. Subsequently, after immersing in the aqueous dispersion of the polymer component B, the mixture was dried at a constant length of 150 ° C. for 120 seconds to obtain a carbon fiber cord. Table 1 summarizes the performance evaluation results of the obtained carbon fiber cord.

[Example 2]
Regarding polymer component A, 415 g of nitrile rubber latex (NIPOL LX1562, manufactured by Nippon Zeon Co., Ltd., concentration 41%) was used instead of hydrogenated nitrile rubber latex (Zetopo12230LX, manufactured by Nippon Zeon Co., Ltd., concentration 40%), and water was used. The carbon fiber cord was bonded in the same manner as in Example 1 except that it was diluted with 348.9 g. Table 1 shows the performance evaluation results of the obtained carbon fiber cord.

[Example 3]
Regarding the polymer component B, the carbon fiber cord was bonded in the same manner as in Example 1 except that zinc oxide and carbon black were not added. Table 1 shows the performance evaluation results of the obtained carbon fiber cord.

[Example 4]
Regarding polymer component A, instead of hydrogenated nitrile rubber latex (Zetopo12230LX, manufactured by Nippon Zeon Co., Ltd., concentration 40%), vinylpyridine styrene-butadiene terpolymer latex (Pyratex, manufactured by Nippon A & L Inc., concentration 42%) 405 g Was used, and the carbon fiber cord was bonded in the same manner as in Example 1 except that it was diluted with 338.9 g of water. Table 1 shows the performance evaluation results of the obtained carbon fiber cord.

[Example 5]
Regarding the polymer component B, the carbon fiber cord was bonded in the same manner as in Example 1 except that 325 g of hydrogenated nitrile rubber latex was used without adding chlorosulfonated polyethylene rubber latex. Table 1 shows the performance evaluation results of the obtained carbon fiber cord.

[Comparative Example 1]
The carbon fiber cord was bonded in the same manner as in Example 1 except that the polymer component B was not bonded. Table 1 shows the performance evaluation results of the obtained carbon fiber cord.

[Comparative Example 2]
The carbon fiber cord was bonded in the same manner as in Example 1 except that the polymer component A was not bonded. Table 1 shows the performance evaluation results of the obtained carbon fiber cord.

[Reference example]
Each of the aqueous dispersions of the polymer component A and the polymer component B was treated by diluting the solid content concentration with water to half, and the carbon fiber cord was bonded in the same manner as in Example 1. Table 1 shows the performance evaluation results of the obtained carbon fiber cord.

The carbon fiber cords obtained in Examples 1 to 5 of the present invention have excellent rubber adhesiveness in a state where the tensile strength is equal to or higher than that of the cords obtained in Comparative Example, and the peeling adhesion test is performed. The rubber adhesion state after that was also a good result.

According to the present invention, it is possible to provide a carbon fiber cord which is significantly improved in adhesiveness to rubber and is suitably used as a core wire of a transmission belt, and conventional carbon fibers have a problem in rubber adhesiveness. It can be suitably used as a core wire of a friction transmission belt or a toothed belt.

Claims (7)

It is a carbon fiber cord in which a resin is attached to the surface of a carbon fiber bundle, and the resin is a polymer component A composed of resorcin, formalin, and rubber latex, and an outer layer of the polymer component A, and is the most of the carbon fiber cord. The outer layer is provided with a polymer component B composed of a nitrile rubber latex and / or a hydride nitrile rubber latex and a cross-linking agent, and the solid content of the polymer component A is 3 to 17% by weight, and the solid content of the polymer component B is 13 to 13 to. 37 wt%, and rubber-reinforcing carbon fiber cord total solid content of the polymer component a and polymer component B is characterized by 20 to 40 wt% der Rukoto. The carbon for rubber reinforcement according to claim 1, wherein the resorcin formalin rubber latex contained in the polymer component A is a resorcin formalin rubber latex containing a nitrile rubber latex and / or a hydride nitrile rubber latex. Fiber cord. The rubber reinforcing carbon fiber according to claim 1 or 2, wherein the polymer component B is a polymer component containing a halogen-containing polymer in addition to a nitrile rubber latex and / or a hydrogenated nitrile rubber latex and a cross-linking agent. code. The rubber reinforcing carbon fiber cord according to claim 1 or 2, wherein the polymer component B is a polymer component containing zinc oxide in addition to the nitrile rubber latex and / or the hydrogenated nitrile rubber latex and the cross-linking agent. .. The rubber reinforcement according to any one of claims 1 to 4, wherein the polymer component B is a polymer component containing carbon black in addition to the nitrile rubber latex and / or the hydrogenated nitrile rubber latex and the cross-linking agent. Carbon fiber cord. The carbon fiber cord for rubber reinforcement according to any one of claims 1 to 5, wherein the cross-linking agent contained in the polymer component B is an isocyanate-based cross-linking agent. Any of claims 1 to 6, wherein the polymer component A containing resorcin, formalin, and hydride nitrile rubber latex as a constituent component and the polymer component B containing hydride nitrile rubber latex and a cross-linking agent as constituent components are provided. Carbon fiber cord for rubber reinforcement described in.