JP2010053495A - Steel cord for reinforcing tire, and pneumatic tire using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steel cord for reinforcing a tire designed to disperse a stress acting on the interface with rubber and improve adhesiveness, and to provide a pneumatic tire using the steel cord and having excellent durability. <P>SOLUTION: The steel cord 1 for reinforcing the tire is obtained by covering the periphery of a steel cord body 2 formed from a single monofilament with a thermoplastic elastomer composition 3 in which an elastomer is dispersed in a thermoplastic resin. The pneumatic tire 6 is obtained by using the steel cord 1 for reinforcing the tire in a belt layer 7 and/or carcass layer 8. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a tire-reinforcing steel cord and a pneumatic tire using the same, and more specifically, a tire-reinforcing steel cord in which stress acting on an interface with rubber is dispersed to improve adhesion, and the same The present invention relates to a pneumatic tire having excellent durability.

  In general, steel cords obtained by twisting a plurality of steel wires have been widely used as steel cords for reinforcing pneumatic tires. However, steel cords made by twisting multiple steel wires not only increase the weight, but also have a problem that the durability of the steel cord itself is likely to deteriorate due to corrosion caused by moisture contained inside the cord. A single monofilament has been used instead of the twisted cord (see, for example, Patent Documents 1 and 2).

  However, since the steel cord made of a single monofilament has a higher elastic modulus than the twisted cord, when this is used as a tire reinforcing cord, the difference in elastic modulus with the surrounding rubber becomes too large. There has been a problem that peeling is likely to occur at the interface between the monofilament and the surrounding rubber due to the load stress acting during tire running. In particular, in the case of a single monofilament, since the contact area with the surrounding rubber is limited, the problem of adhesiveness has been a major obstacle.

In order to improve the adhesion at such an interface, conventionally, metal plating such as copper or zinc has been performed around the monofilament, and organic acid heavy metal salts such as cobalt naphthenate have been blended into the coated rubber. . However, in the method of metal plating around the monofilament, there is a problem that the metal plating diffuses to the surrounding rubber through long-term use and promotes deterioration of the rubber, and in the method of blending organic acid heavy metal salt with the coated rubber However, there is a problem that the deterioration of the coated rubber is promoted by blending a large amount of the organic acid heavy metal salt, and none of these methods is yet sufficient as a measure for improving the adhesiveness of the steel cord made of monofilament.
JP 2003-313369 A JP 2004-58727 A

  An object of the present invention is to eliminate the above-mentioned conventional problems, and to reinforce the tire by dispersing stress acting on the interface with the rubber without deteriorating the surrounding rubber. It is to provide a steel cord for use and a pneumatic tire excellent in durability using the same.

  The steel cord for reinforcing tires according to the present invention that achieves the above object is characterized in that a thermoplastic elastomer composition in which an elastomer is dispersed in a thermoplastic resin is coated around a steel cord body made of a single monofilament. Is.

  Moreover, in the structure mentioned above, it is preferable to comprise as described in the following (1)-(3).

(1) The thickness of the thermoplastic elastomer composition is 0.03 mm or more.
(2) An adhesive layer is interposed at the interface between the steel cord and the thermoplastic elastomer composition.
(3) A die forming process is performed in the longitudinal direction of the steel cord.

  The pneumatic tire of the present invention is characterized by using the above-described tire reinforcing steel cord for a belt layer and / or a carcass layer.

  According to the above-described present invention, the steel cord for reinforcing tires is composed of a steel cord body made of a single monofilament, and a thermoplastic elastomer composition in which an elastomer is dispersed in a thermoplastic resin around the steel cord body. Since the material is covered, the stress applied to the interface between the steel cord body and the surrounding rubber during tire running is relieved by the appropriate flexibility and rigidity of the thermoplastic resin and elastomer in the thermoplastic elastomer composition. As a result, good adhesiveness is ensured, and at the same time, the water contained in the rubber is prevented from reaching the surface of the steel cord body by the intervention of the thermoplastic elastomer composition. In order to suppress corrosion, the durability of the tire can be improved.

  In addition, since the thermoplastic elastomer composition is coated around the steel cord body, the surrounding rubber is not deteriorated, and further, the steel cord body is not required to be twisted. A steel cord for reinforcing a tire excellent in weight reduction and a pneumatic tire using the same can be obtained.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a sectional view showing a tire reinforcing steel cord according to an embodiment of the present invention, and FIG. 2 is a sectional view of a tire reinforcing layer showing a state in which a plurality of tire reinforcing steel cords of FIG. It is.

  In FIG. 1, a steel cord 1 for reinforcing tires is composed of a steel cord body 2 made of a single monofilament and a thermoplastic elastomer composition 3 in which an elastomer is dispersed in a thermoplastic resin coated around the steel cord body 2. ing. As shown in FIG. 2, a plurality of tire reinforcing steel cords 1 configured as described above are aligned and embedded in rubber 4 to form a tire reinforcing layer 5.

  With this configuration, the stress applied to the interface between the steel cord main body 2 and the surrounding rubber 4 during running of the tire is moderately flexible and rigid due to the thermoplastic resin and elastomer in the thermoplastic elastomer composition 3. As a result, the adhesion of the thermoplastic elastomer 3 is prevented and water contained in the rubber 4 is prevented from reaching the surface of the steel cord body 3. Since the corrosion of the steel cord main body 3 is suppressed, the durability of the tire can be improved.

  In addition, since the thermoplastic elastomer composition 3 is coated around the steel cord body 2, the surrounding rubber 4 is not deteriorated, and further, the twisting step of the steel cord body 2 is not required. Thus, it is possible to obtain a tire reinforcing steel cord 1 which is inexpensive and excellent in weight reduction, and a pneumatic tire using the same.

  As the thermoplastic resin constituting the thermoplastic elastomer composition 3 described above, for example, a polyamide resin [for example, nylon 6 (N6), nylon 66 (N66), nylon 46 (N46), nylon 11 (N11), nylon 12 (N12), nylon 610 (N610), nylon 612 (N612), nylon 6/66 copolymer (N6 / 66), nylon 6/66/610 copolymer (N6 / 66/610), nylon MXD6 ( MXD6), nylon 6T, nylon 6 / 6T copolymer, nylon 66 / PP copolymer, nylon 66 / PPS copolymer] and their N-alkoxyalkylated products, for example, methoxymethylated products of nylon 6, nylon 6 / 610 copolymer methoxymethylated, nylon 612 methoxymethylated, poly Stell resin (for example, polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyethylene isophthalate (PEI), PET / PEI copolymer, polyarylate (PAR), polybutylene naphthalate (PBN), liquid crystal polyester, Aromatic polyester such as polyoxyalkylene diimide diacid / polybutylene terephthalate copolymer], polynitrile resin [for example, polyacrylonitrile (PAN), polymethacrylonitrile, acrylonitrile / styrene copolymer (AS), (meth) Acrylonitrile / styrene copolymer, (meth) acrylonitrile / styrene / butadiene copolymer], polymethacrylate resin [for example, polymethyl methacrylate (PMMA), polyethyl methacrylate], poly Vinyl resins [eg, vinyl acetate, polyvinyl alcohol (PVA), vinyl alcohol / ethylene copolymer (EVOH), polyvinylidene chloride (PDVC), polyvinyl chloride (PVC), vinyl chloride / vinylidene chloride copolymer, chloride Vinylidene / methyl acrylate copolymer, vinylidene chloride / acrylonitrile copolymer], cellulose resin [for example, cellulose acetate, cellulose acetate butyrate], fluorine resin [for example, polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF) Polychlorofluoroethylene (PCTFE), tetrafluoroethylene / ethylene copolymer], imide resin [for example, aromatic polyimide (PI)] and the like are preferably used.

  Examples of the elastomer constituting the thermoplastic elastomer composition 3 include diene rubbers and hydrogenated products thereof [for example, natural rubber (NR), isoprene rubber (IR), epoxidized natural rubber, styrene butadiene rubber. (SBR), butadiene rubber (BR, high cis BR and low cis BR), nitrile rubber (NBR), hydrogenated NBR, hydrogenated SBR], olefin rubber [eg, ethylene propylene rubber (EPDM, EPM), maleic acid Modified ethylene propylene rubber (M-EPM), butyl rubber (IIR), isobutylene and aromatic vinyl or diene monomer copolymer, acrylic rubber (ACM), ionomer], halogen-containing rubber [for example, Br-IIR, CI-IIR , Bromide of isobutylene paramethylstyrene copolymer (Br- PMS), chloroprene rubber (CR), hydrin rubber (CHR), chlorosulfonated polyethylene rubber (CSM), chlorinated polyethylene rubber (CM), maleic acid-modified chlorinated polyethylene rubber (M-CM)], silicon rubber [for example, Methyl vinyl silicone rubber, dimethyl silicone rubber, methyl phenyl vinyl silicone rubber), sulfur-containing rubber (for example, polysulfide rubber), fluorine rubber (for example, vinylidene fluoride rubber, fluorine-containing vinyl ether rubber, tetrafluoroethylene-propylene rubber, Fluorine-containing silicone rubber, fluorine-containing phosphazene rubber), thermoplastic elastomer (for example, styrene elastomer, olefin elastomer, ester elastomer, urethane elastomer, polyamide elastomer) ] And the like are preferably used.

  When the thermoplastic resin and the elastomer described above have different compatibility, they can be made compatible by using a suitable compatibilizing agent as the third component. By mixing the compatibilizer with the blend system, the interfacial tension between the thermoplastic resin and the elastomer decreases, and as a result, the rubber particle size forming the dispersion layer becomes finer, so the characteristics of both components are more It will be expressed effectively. Such a compatibilizing agent generally includes a copolymer having a structure of both or one of a thermoplastic resin and an elastomer, or an epoxy group, a carbonyl group, a halogen group, and an amino group that can react with the thermoplastic resin or elastomer. In addition, a copolymer having a oxazoline group, a hydroxyl group and the like can be taken. These may be selected according to the type of thermoplastic resin and elastomer to be mixed, but those commonly used include styrene / ethylene butylene block copolymer (SEBS) and its maleic acid modified product, EPDM, EPM, EPDM / styrene or EPDM / acrylonitrile graft copolymer and its modified maleic acid, styrene / maleic acid copolymer, reactive phenoxin and the like can be mentioned. The amount of the compatibilizer is not particularly limited, but preferably 0.5 to 10 parts by weight with respect to 100 parts by weight of the polymer component (the total of the thermoplastic resin and the elastomer).

  The composition ratio of the thermoplastic resin and the elastomer described above is not particularly limited, and may be appropriately determined so as to have a structure in which the elastomer is dispersed as a discontinuous phase in the matrix of the thermoplastic resin, but preferably is a weight. The ratio may be in the range of 70/30 to 30/70. Here, if the blending amount of the above-described elastomer is excessively increased, the water vapor permeability of the thermoplastic elastomer composition 3 is lowered and the steel cord body 2 is easily corroded, and conversely if it is excessively reduced, the thermoplastic elastomer composition. The hardness of No. 3 becomes high and the dynamic fatigue property of the tire decreases.

  In the present invention, the above-described thermoplastic elastomer composition can be mixed with other polymers such as the compatibilizer described above. The purpose of mixing other polymers is to improve the compatibility between the thermoplastic resin and the elastomer, to improve the molding processability of the material, to improve the heat resistance, to reduce the cost, etc. Examples of the material that can be used include polyethylene (PE), polypropylene (PP), polystyrene (PS), ABS, SBS, and polycarbonate (PC). In addition, fillers (calcium carbonate, titanium oxide, alumina, etc.) generally blended into polymer blends, reinforcing agents such as carbon black and silica, softeners, plasticizers, processing aids, pigments, dyes, anti-aging An agent or the like can be optionally blended.

  The thermoplastic elastomer composition 3 thus obtained has a structure in which an elastomer component is dispersed as a discontinuous phase in a thermoplastic resin matrix. By taking such a structure, it is possible to provide both sufficient flexibility and sufficient rigidity due to the effect of the resin layer as a continuous phase, and at the time of molding, the thermoplastic resin can be used regardless of the amount of the elastomer component. Equivalent moldability can be obtained.

  Further, the elastomer described above can be dynamically vulcanized when mixed with a thermoplastic resin. The vulcanizing agent, vulcanization aid, vulcanization conditions (temperature, time), and the like in the case of dynamic vulcanization may be appropriately determined according to the composition of the elastomer to be added, and are not particularly limited.

  As the vulcanizing agent, a general rubber vulcanizing agent (crosslinking agent) can be used. Specific examples of the sulfur vulcanizing agent include powdered sulfur, precipitated sulfur, highly dispersible sulfur, surface-treated sulfur, insoluble sulfur, dimorpholine disulfide, alkylphenol disulfide, and the like. About 4 phr can be used. Here, “phr” refers to parts by weight per 100 parts by weight of the elastomer component.

  Moreover, you may add a vulcanization accelerator as needed. Examples of the vulcanization accelerator include general vulcanization accelerators such as aldehyde / ammonia, guanidine, thiazole, sulfenamide, thiuram, dithioate, thiourea, etc. About 2 phr can be used.

  Moreover, as a vulcanization | cure acceleration | stimulation adjuvant, the general rubber adjuvant can be used together, for example, zinc oxide (0.5-3phr), stearic acid, oleic acid, and these Zn salt (0. 5-4 phr) can be used.

  The thermoplastic elastomer composition 3 is produced by a method in which a thermoplastic resin and an elastomer (unvulcanized material in the case of rubber) are previously melt-kneaded with a twin-screw kneading extruder or the like to form a continuous phase (matrix). By dispersing the elastomer as a dispersed phase (domain) in the resin. When the elastomer is vulcanized, a vulcanizing agent may be added under kneading to dynamically vulcanize the elastomer. Further, various compounding agents (excluding the vulcanizing agent) for the thermoplastic resin or elastomer may be added during the kneading, but it is preferable to mix them in advance before kneading.

  As a kneading machine used for kneading the thermoplastic resin and the elastomer, a screw extruder, a kneader, a Banbury mixer, a biaxial kneading extruder, or the like can be used. Among them, it is preferable to use a twin-screw kneading extruder for kneading the thermoplastic resin and the elastomer and for dynamic vulcanization of the elastomer. Further, two or more types of kneaders may be used and kneaded sequentially.

  The steel cord 1 for tire reinforcement of the present invention is formed by molding the above-described thermoplastic elastomer composition 3 so as to cover the periphery of the steel cord body 2 using an extrusion molding machine or the like. A tire reinforcing layer 5 is formed by embedding in a rubber 4 by a plurality of parallel aligning calendar devices.

  In the present invention, the thickness t (see FIG. 1) of the thermoplastic elastomer composition 3 covering the periphery of the steel cord body 2 is not particularly limited, but the steel cord body 2 and the surrounding rubber 4 are not limited. From the viewpoint of efficiently dispersing the stress applied to the interface and securing a good adhesive force, the thickness t is set to 0.03 mm or more, preferably 0.05 to 0.5 mm. When the thickness t is less than 0.03 mm, it becomes difficult to relieve the stress acting on the interface between the steel cord main body 2 and the surrounding rubber 4, and this causes peeling at this interface. However, if the thickness t is excessively increased, the effect of reducing the weight cannot be obtained.

  More preferably, an adhesive layer is interposed between the monofilament 2 and the thermoplastic elastomer composition 3. Thereby, the favorable adhesive force between the monofilament 2 and the thermoplastic elastomer composition 3 is ensured, and durability as the tire reinforcement layer 5 can be improved reliably. The material constituting the adhesive layer is not particularly limited, and an epoxy resin-based adhesive or a urethane resin-based adhesive that is usually used as an adhesive can be used.

  Since the tire reinforcing steel cord 1 obtained in this way is not twisted, its extensibility is insufficient depending on the required characteristics of the tire. Therefore, in order to impart extensibility, it is preferable to perform a die-forming process in the longitudinal direction of the steel cord body 2 in accordance with the required characteristics of the tire. The form forming process in this case is not particularly limited, but may be formed in a wave shape or a spiral shape as illustrated in FIG. 3 as a cross section of the steel cord body 2. And the desired elongation according to the required characteristic of a tire is securable by adjusting suitably the size (pitch, height, etc.) of the shaping in this shaping process.

  The tire-reinforcing steel cord 1 of the present invention thus obtained is formed in the tire reinforcing layer 5 as shown in FIG. The tire reinforcing layer 5 is used for the belt layer 7 and / or the carcass layer 8 of the pneumatic tire 6 as shown in FIG. Thereby, a pneumatic tire excellent in durability while being inexpensive and lightweight can be obtained.

  In the embodiment of FIG. 2, the case where the steel cords embedded in the rubber 4 are all made of only the tire reinforcing steel cord 1 of the present invention is illustrated, but the tire reinforcing layer 5 is provided with other types of reinforcing cords. May be buried together. That is, when the tire reinforcing steel cord 1 of the present invention is used for the belt layer 7 or the carcass layer 8, the reinforcing cord embedded in the rubber 4 is made of, for example, steel or organic, depending on the required characteristics of the tire. In combination with a twisted cord made of fiber or the like, these various reinforcing cords may be arranged in a regular or random manner together with the tire reinforcing steel cord 1 of the present invention, and then embedded in the rubber 4.

  The tire size is 195 / 65R15, the tire structure is shown in FIG. 4, and the steel cord constituting the belt layer is a steel monofilament with a wire diameter of 0.40 mm. Comparative tires (comparative examples) and tires according to the present invention (examples 1 to 3) were produced, with the same specifications, with the presence or absence of the coating layer and the adhesive layer and the materials thereof as shown in Table 2. The number of steel cords driven in each tire was 35/50 mm, and the material shown in Table 1 was used for the coating layer in the tire of the present invention, and the thickness was 0.1 mm.

  For these four types of tires, in order to evaluate the durability of the steel cords constituting the belt layer, the tire durability before and after immersion in a saline solution was evaluated by the following test method. The results were evaluated in three stages of A, B, and C before and after immersion in a saline solution, and are also shown in Table 2. A is the best and C is the worst.

[Evaluation of tire durability before immersion in saline solution]
After each tire is assembled and filled with air pressure of 170 kPa, the ambient temperature is controlled to 38 ± 3 ° C. using an indoor drum tester, and the speed is set to 30 km / h on a drum with a flat surface (constant) ), Running for 10 hours while changing the load load and slip angle with a short waveform of 0.083 Hz under the fluctuation condition where the slip angle is 0 ± 5 ° and the load is 70 ± 40% of the maximum load specified by JATMA. I let you. The tire after running was cut open, the state of breakage of the steel cord constituting the belt layer was examined, and the number of breakage points was regarded as “Evaluation of tire durability before immersion in saline solution”.

[Evaluation of tire durability after immersion in saline solution]
A cutting knife having a length of 30 mm and a depth of 3.0 mm along the circumferential direction of the tire is formed on the bottom of the main groove of each tire at eight positions on the circumference at equal intervals, and a rim is assembled and filled with an air pressure of 200 kPa. After rolling for 3 minutes in a water channel filled with a 1.0 wt% saline solution so that all the cut flaws were immersed in the solution, it was left in a room where the ambient temperature was controlled to 50 ± 5 ° C. for 24 hours. After repeating this operation 5 times, a running test on the drum described above was performed, and the state of breakage of the steel cord was examined in the same manner as described above. Evaluation of tire durability ".

  From Table 2, the tire of the present invention in which the periphery of the steel cord main body in the steel cord constituting the belt layer was coated with the thermoplastic elastomer composition was compared with the comparative tire in which the periphery of the steel cord main body was not coated. It can be seen that the durability is improved. In particular, the results of evaluation after immersion in a saline solution show that the steel cord for reinforcing tires of the present invention is excellent in corrosion resistance.

It is sectional drawing which shows the steel cord for tire reinforcement by embodiment of this invention. FIG. 2 is a cross-sectional view of a tire reinforcing layer showing a state in which a plurality of tire reinforcing steel cords of FIG. 1 are aligned and embedded in rubber. It is sectional drawing which shows an example of the shaping | molding form of the steel cord by embodiment of this invention. It is a half sectional view showing the structure of a tire adopted in an example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steel cord for tire reinforcement 2 Steel cord main body 3 Thermoplastic elastomer composition 4 Rubber 5 Reinforced rubber layer 6 Pneumatic tire 7 Belt layer 8 Carcass layer

Claims (5)

  A steel cord for reinforcing tires, in which a thermoplastic elastomer composition in which an elastomer is dispersed in a thermoplastic resin is coated around a steel cord body made of a single monofilament.   The steel cord for tire reinforcement according to claim 1, wherein a thickness of the thermoplastic elastomer composition is 0.03 mm or more.   The steel cord for reinforcing tires according to claim 1 or 2, wherein an adhesive layer is interposed at an interface between the steel cord body and the thermoplastic elastomer composition.   The steel cord for reinforcing a tire according to any one of claims 1 to 3, wherein the steel cord main body is subjected to a mold forming process in a longitudinal direction.   A pneumatic tire using the steel cord for tire reinforcement according to any one of claims 1 to 4 for a belt layer and / or a carcass layer.

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