JP6266881B2 - Steel cord for rubber reinforcement and pneumatic tire - Google Patents

Description

  The present invention relates to a steel cord used as a reinforcing material for rubber products such as tires, and a pneumatic tire using the steel cord.

  A pneumatic radial tire generally includes a belt in which a plurality of belt plies are crossed and laminated between an outer surface of a carcass ply and a tread rubber, and the belt ply includes steel having excellent tensile strength and tensile elasticity. Code is being used. Conventionally, as such a steel cord, one obtained by twisting a plurality of filaments is generally used. For example, a 1 × n structure (n = 3 to 5) or a m + n structure in which metal filaments are twisted around a plurality of aligned filaments can be used.

  In recent years, pneumatic radial tires have been required to be lighter due to demands for lower fuel consumption of vehicles, and it has been considered to reduce the weight of belts by reducing the thickness of rubber covering steel cords. Yes. As one of the concrete means, a flat steel cord is proposed in which a plurality of filaments are arranged in parallel, and a single metal filament is wound around and wrapped around the filament (see Patent Documents 1 to 3). ). However, when a steel filament is used for the wrapping material in this way, fretting wear occurs on the main filament due to friction with the main filament, which causes a reduction in the strength of the steel cord.

  Patent Document 4 discloses using an organic fiber as a wrapping material in order to suppress such fretting wear. Patent Document 5 discloses that a polymer material having a melting point of 50 to 200 ° C. that melts during tire vulcanization molding is used as the wrapping material. However, if organic fibers are used as they are, the shape is unstable, and it is difficult to maintain a cord shape composed of bundles of main filaments arranged in a line. Further, even with a wrapping material that melts at the time of vulcanization molding, it is difficult to maintain the cord shape in the same manner because the organic fiber remains as it is before vulcanization.

JP 2002-069873 A JP 2012-106570 A JP 2012-107353 A JP 2001-55008 A Japanese Patent Laid-Open No. 2001-131884

  An object of the present invention is to provide a steel cord for rubber reinforcement capable of maintaining a cord shape while suppressing fretting wear in a steel cord in which metal filaments are aligned.

The method for producing a steel cord for reinforcing rubber according to the present invention is a steel cord obtained by winding a wrapping material around a bundle of main filaments arranged in a line without twisting a plurality of metal filaments, the wrapping material there Ru der those cured impregnated with a curable resin to the non-metallic fibers, a method for producing a steel cord for rubber reinforcement,
Using a mold having a flat cross-sectional shape corresponding to the main filament bundle, a non-metallic fiber impregnated with a curable resin, which is an epoxy resin composition in which crosslinked rubber particles are blended with an epoxy resin, is wound around the mold Thereafter, the wrapping material is molded by heating and curing the curable resin, and after the molded wrapping material is removed from the mold, the wrapping material is wound around the bundled main filaments. .

The method for producing a pneumatic tire according to the present invention is to produce a steel cord for rubber reinforcement by the above method , and produce a pneumatic tire using the rubber cord for rubber reinforcement as a belt ply.

  According to the present invention, since the wrapping material is made of non-metallic fiber impregnated with a curable resin and cured, the cord shape is maintained while suppressing fretting wear as in the case of using a steel filament as the wrapping material. Can do.

1 is a half sectional view of a pneumatic radial tire according to one embodiment. It is a partial cross section figure of the belt ply which concerns on one Embodiment. It is a figure showing the composition of the steel cord concerning one embodiment. It is sectional drawing of the type | mold for shaping | molding a wrapping material.

  Hereinafter, embodiments of the present invention will be described in detail.

  As shown in FIG. 1, the pneumatic tire according to the embodiment is a pneumatic radial tire for passenger cars, and includes a pair of left and right bead portions (1) and sidewall portions (2), and left and right sidewall portions (2). And tread portions (3) provided between both sidewall portions (2) so as to connect the radially outer ends of the two, and straddle between the pair of bead portions (1). An extending carcass (4) is provided.

  The carcass (4) extends from the tread portion (3) to the sidewall portion (2), and at least one piece of which both ends are locked by an annular bead core (5) embedded in the bead portion (1). Consists of carcass plies. The carcass ply is formed by arranging carcass cords made of organic fiber cords or the like substantially perpendicular to the tire circumferential direction.

  A belt (7) is disposed between the carcass (4) and the tread rubber portion (8) on the outer peripheral side of the carcass (4) in the tread portion (3) (that is, the outer side in the tire radial direction). The belt (7) is provided so as to overlap the outer periphery of the crown portion of the carcass (4), and can be constituted by one or a plurality of belt plies, usually at least two belt plies. The first belt ply (7A) on the carcass (4) side and the second belt ply (7B) on the tread rubber portion (8) side are constituted by two belt plies. On the outer peripheral side of the belt (7), there is a belt reinforcing layer (9) made of an organic fiber cord spirally wound at an angle of 0 to 5 degrees with respect to the tire circumferential direction, and the entire width direction of the belt (7). It is provided so as to cover.

  The belt plies (7A) and (7B) are formed by inclining the steel cord (10) at a predetermined angle (for example, 15 to 35 degrees) with respect to the tire circumferential direction and arranging the steel cord (10) at predetermined intervals in the tire width direction. As shown in FIG. 2, it is covered with a coating rubber (11). The steel cord (10) is disposed so as to intersect each other between the two belt layers (7A) and (7B).

  In this embodiment, as shown in FIG. 3, as a steel cord (10), a main filament bundle in which metal filaments (hereinafter referred to as main filaments) (12) are arranged in a line without being twisted together. A flat cord having an n + 1 structure including (13) and one wrapping material (14) wound around the main filament bundle (13) is used.

  As the main filament (12), steel filaments made of various carbon steels can be used, and the diameter (filament diameter) d is not particularly limited. For example, the diameter d may be 0.15 to 0.30 mm.

  The main filament bundle (13) can be formed by arranging a plurality of main filaments (12) having the same diameter so as to be arranged in a horizontal line without being twisted. That is, the main filaments (12) are juxtaposed so as to form one layer along one plane. Therefore, the steel cord (10) obtained is flat and has a major axis D1 and a minor axis D2 as shown in FIG. The values of the major axis D1 and the minor axis D2 are not particularly limited. For example, the major axis D1 may be 1.00 to 1.50 mm, and the minor axis D2 may be 0.30 to 0.60 mm. The number of main filaments (12) constituting the main filament bundle (13) (n above) is not particularly limited. For example, the number may be 2 to 6 (that is, n = 2 to 6), more preferably 3 to 6.

  As shown in FIG. 3, the main filament (12) may be a straight metal filament that is not corrugated, or may be a corrugated metal filament. When corrugating, the main filament is preferably corrugated only in the major axis direction of the steel cord, that is, it is corrugated two-dimensionally in a plane along the major axis direction and the longitudinal direction. In this case, a plurality of metal filaments molded in the longitudinal direction with the same wave height and wavelength may be used. In this case, the corrugated phases may be aligned by aligning the plurality of metal filaments, or may be aligned by shifting the phases.

  The steel cord (10) is formed by spirally wrapping a wrapping material (14) around the main filament bundle (13). In this embodiment, a non-metallic fiber impregnated with a curable resin is used as the wrapping material (14). In general, since non-metallic fibers are softer than steel filaments, fretting wear on the main filament (12) can be suppressed by using such non-metallic fibers as the wrapping material (14). In addition, the effect of maintaining the cord shape can be exhibited by impregnating and curing a curable resin, instead of using the nonmetallic fiber as it is. Therefore, both fretting resistance and cord shape retention can be achieved.

  As the non-metallic fiber, it is preferable to use a high-strength fiber from the viewpoint of winding workability with respect to the main filament bundle (13) and cord shape retention after winding. Specifically, it is preferable to use a fiber having a tensile strength of 2000 MPa or more. In addition, although the upper limit of tensile strength is not specifically limited, Usually, it is 6000 MPa or less.

  Examples of such high-strength non-metallic fibers include high-strength organic fibers such as aramid fibers, wholly aromatic polyester fibers, polyparaphenylene benzoxazole fibers (PBO fibers), and polyvinyl alcohol fibers (high-elasticity PVA fibers). A carbon fiber etc. can be mentioned. These may be used alone or in combination of two or more.

  Examples of the aramid fiber include para-aramid fiber and meta-aramid fiber, and examples of the former include “Kevlar” manufactured by Toray DuPont, “Twaron” manufactured by Teijin Techno Products, “Technora”, and the like. Examples of the latter include “Nomex” manufactured by DuPont and “Conex” manufactured by Teijin Techno Products. Examples of wholly aromatic polyester fibers include “Vectran” manufactured by Kuraray Co., Ltd., “Zylon” manufactured by Toyobo Co., Ltd. as PBO fibers, and “Kuraron K-II” manufactured by Kuraray Co., Ltd. as high-elasticity PVA fibers. Examples of the carbon fiber include PAN-based carbon fiber and pitch-based carbon fiber.

  In addition, as such a non-metallic fiber, you may use as it is without twisting the yarn which bundles many filaments, you may use the cord of the single twist structure formed by twisting this yarn, You may use the cord of the double twist structure formed by twisting this yarn.

  The thickness of the wrapping material (14) differs depending on the material and is not particularly limited, but in the case of organic fibers, it is preferably 400 to 1670 dtex. Moreover, in the case of carbon fiber, it is preferable that they are 1000 filaments-6000 filaments.

  It is preferable to use a thermosetting resin as the curable resin. For example, an unsaturated polyester resin, an epoxy resin, a cyanate ester resin, etc. can be mentioned. Preferably, an epoxy resin is used. More specifically, it is preferable to use an epoxy resin composition in which a curing agent and crosslinked rubber particles as a toughness imparting agent are blended in an epoxy resin as a main agent.

  The main agent is preferably a liquid bisphenol type epoxy resin, particularly preferably a liquid low viscosity bisphenol F type epoxy resin.

  As the curing agent, those generally used for epoxy resins can be used, and contain functional groups such as carboxylic anhydride groups, carboxyl groups, carboxylic acid hydrazide groups, amino groups, hydroxyl groups, mercapto groups, etc. And known organic compounds. Specifically, acid anhydride-based curing agents (such as methyl nadic anhydride), amine-based curing agents (such as metaphenylenediamine, methyldianiline, ethylmethylimidazole, isophoronediamine), polyaminoamide-based curing agents, phenol-based curing Agents (such as bisparaxyloxyphenyl sulfone), polymercaptan curing agents, and latent curing agents (such as dicyandiamide). Particularly preferred are acid anhydride curing agents such as methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methyl nadic anhydride, methyl hymic anhydride and the like.

  Examples of the crosslinked rubber particles that are toughness imparting agents include NBR (nitrile rubber), SBR (styrene rubber), BR (butadiene rubber), CR (chloroprene rubber), IIR (butyl rubber), EPDM (ethylene-propylene rubber), Examples thereof include fine rubber particles such as CSM (chlorosulfonated rubber), urethane rubber, polysulfide rubber, silicone rubber, and fluorine rubber.

  The impregnation amount of the curable resin with respect to the nonmetallic fiber (the amount of adhesion as a solid) is not particularly limited, but is preferably 10 to 40 parts by mass, more preferably 20 to 100 parts by mass with respect to 100 parts by mass of the nonmetallic fiber. 30 parts by mass.

  The winding pitch p when the wrapping material (14) is wound around the main filament bundle (13) is not particularly limited, and can be set to, for example, 2.0 to 30.0 mm.

  The wrapping method using such a wrapping material (14) is not particularly limited, but includes the following two typical methods.

  The first method uses a mold having a flat cross-sectional shape (see FIG. 4) corresponding to the main filament bundle (13), and non-metallic fibers impregnated with a curable resin are placed around the mold at a predetermined pitch. After winding, it molds by heating and curing the curable resin. Then, it removes from a type | mold and it winds around the bundle | flux of the main filament (13) gathered separately as a wrapping material (14) after the non-metallic fiber obtained after shaping | molding.

  In the second method, a nonmetallic fiber impregnated with a curable resin is used as a wrapping material (14), and the wrapping material (14) is wound around a separately aligned main filament bundle (13) at a predetermined pitch. Thereafter, the curable resin is heated and cured.

  As shown in FIG. 2, the belt ply (7A) (7B) has the steel cord (10) arranged such that the major axis direction (B) thereof is parallel to the belt surface (that is, the belt outer peripheral surface). Is formed. That is, in the belt ply, the steel cord (10) is embedded in the cord covering rubber (11) at a predetermined interval so that the short diameter direction (A) thereof coincides with the thickness direction (K) of the belt ply. ing. Therefore, the steel cord (10) is disposed so that the major axis direction (B) is parallel to the tread surface. With this configuration, it is easy to process the steel cord (10) when it is covered with rubber, and the thickness of the belt ply can be reduced to suppress an increase in tire mass. In addition, since the obtained belt ply has high bending rigidity in the tire width direction, it is possible to improve steering stability performance.

  The number of ends of the steel cord (10) in the belt ply (the number of driven wires) can be appropriately set according to the cord tensile strength and the like, and is not particularly limited, but is preferably 10-25 wires / 25 mm.

  In the above embodiment, the case where the steel cord (10) is used for the belt ply has been described. However, the steel cord (10) is not limited to the belt ply, and may be used for a carcass ply, for example. Moreover, it can use as a reinforcing material of not only a tire but various rubber products, such as a conveyor belt, for example.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to these Examples.

  Each measuring method in an Example is as follows.

Filament diameter and cord diameter: Based on JIS G3510, the diameters of the metal filament and the steel cord were measured with a predetermined thickness meter. For the cord diameter, the outer diameter on the longer diameter side (major diameter D1) and the outer diameter on the shorter diameter side (minor diameter D2) were measured.

-Tensile strength of wrapping material fibers: Strength was determined from fineness and tensile strength in accordance with JIS L1017. Shimadzu Corporation autograph was used for the tensile test.

-Cord shape retention performance: Two arbitrary positions on the tire circumference were cut at two positions (the positions of both are 90 ° or more apart), and the arrangement of the cords was observed on the cut surfaces. A total of 90 cords were observed, 15 at each end of the two belt plies per cross section and 15 at the center. Then, the ratio (%) of the number of cords having the minor axis / major axis> 0.5 was calculated, and the value is shown in the table. The smaller this value is, the better the cord shape is maintained.

・ Cord strength retention rate: After mounting a tire with a rim and air pressure of JATMA YEAR BOOK 2012 as described in JATMA YEAR BOOK 2012 on a passenger car, turning the 8-shaped course with two circles with a diameter of 14 m, turning the tire 400 times Was disassembled, the steel cord was taken out, and the cord strength (tensile strength) was measured. Further, the cord strength was measured in the same manner using a steel cord taken out from a non-running tire, and the retention rate (%) of the cord strength after running with respect to the cord strength of the non-running tire was calculated. The higher the retention rate, the less the strength drop due to fretting wear, and the better the durability. The cord strength was calculated by measuring the strength and elongation characteristics of a steel cord using a tensile tester (manufactured by Shimadzu Corporation) according to JIS G3510.

  Steel cords having the structure shown in Table 1 below were produced.

  In detail, the steel cord of the conventional example was produced by twisting five steel filaments drawn to 0.2 mm.

  In Comparative Example 1, five steel filaments drawn to 0.2 mm were aligned in a line without being twisted, and then 0.15 mm soft iron filament (carbon content = 0.72 mass%) was used. Wrapped.

  In Comparative Examples 2 and 3, five steel filaments drawn to 0.2 mm were aligned in a line without being twisted, and then a 500 dtex / 1 single twist polyester cord or a 420 dtex / 1 single twist aramid cord. Wrapped using. In addition, about the comparative example 2, when it wrapped at the same speed as another example, since the polyester code | cord cut and it was not able to wind, it produced by reducing the winding speed until winding was attained.

  In Examples 1 and 2, first, each fiber cord impregnated with an epoxy resin composition as a matrix was wound around a mold having a cross-sectional shape shown in FIG. 4 and then heated at 130 ° C. for 30 minutes. The epoxy resin was cured. Then, it removed from the type | mold and wound the type | molded fiber cord. Next, five steel filaments drawn to 0.2 mm were aligned in a line without twisting, and then wrapped using the typed fiber cord obtained above.

  Here, as the fiber cord, in Example 1, a 420 dtex / 1 single twist aramid cord was used. In Example 2, 1000 carbon fiber filaments were used. Moreover, as an epoxy resin composition, a thermosetting liquid low-viscosity bisphenol A type epoxy resin (epoxy resin manufactured by Japan Epoxy Resin Co., Ltd.) is a main component, and methyltetrahydro is used as a curing agent with respect to 100 parts by mass of the epoxy resin. A blend of 100 parts by mass of phthalic anhydride (manufactured by Hitachi Chemical Co., Ltd.) and 5 parts by mass of ethylene propylene rubber (EPDM) latex (manufactured by Sumitomo Seika Co., Ltd.) as a toughness imparting agent was used. The amount of impregnation of the curable resin with respect to the fibers (adhesion amount as solid content) was 20 parts by mass with respect to 100 parts by mass of the fibers.

  In the steel cords of the examples and comparative examples, the winding pitch p of the wrapping material was set to 4.5 mm.

  Using the obtained steel cord as a belt cord, a radial tire having a tire size of 195 / 50R15 82H having a cross-sectional shape shown in FIG. 1 was vulcanized and molded according to a conventional method. For each tire, the configuration other than the belt was the same.

  The angle of the steel cord in the belt ply (7A) / (7B) was + 25 ° / −25 ° with respect to the tire circumferential direction. The number of steel cord ends was 15 / 25.4 mm. The belt ply was prepared by setting the topping gauge as shown in Table 1 so that the rubber coating thicknesses of the upper and lower steel cords were 0.2 mm, and using a calendar device as the topping counter. At that time, in the example and the comparative example, the steel cord was disposed so that the major axis direction thereof was parallel to the belt surface. The mass of the produced topping was measured, and the belt mass per tire was calculated.

  The carcass ply was 1 ply with a polyester cord of 1670 dtex / 2 and a driving number of 22/25 mm. The belt reinforcing layer was made of nylon 66 cord 1400 dtex / 1 and the number of driven-in wires 24/25 mm.

  About each obtained tire, cord shape retention performance and cord strength retention were measured. The results are shown in Table 1.

  As shown in Table 1, the belt mass is small and the weight is reduced in the comparative example 1 using the flat steel cord of the n + 1 structure as compared with the conventional example using the steel cord of the conventional multi-layer twist structure. It was. However, in Comparative Example 1, since the steel filament was used as the wrapping material to be wound around the main filament bundle, the cord strength retention was lowered due to fretting wear, and the durability was poor.

  In Comparative Example 2, the polyester cord was used as the wrapping material, so that the cord strength retention rate due to fretting wear was improved as compared with Comparative Example 1, but the cord shape retention performance was inferior and the steel cord shape was sufficient. Could not be maintained. The same was true for Comparative Example 3 using an aramid cord as the wrapping material.

  On the other hand, in Example 1 using an aramid cord impregnated and cured with an epoxy resin as a wrapping material, the fretting wear was suppressed and the cord strength was maintained, and the cord shape retention performance was excellent. The shape of the steel cord was maintained. The same was true for Example 2 in which a carbon fiber impregnated and cured with an epoxy resin was used as the wrapping material.

  As described above, according to the present embodiment, the non-metallic fiber is used as the wrapping material, and the fiber is impregnated with a curable resin and cured, thereby achieving both fretting resistance and maintaining the shape of the steel cord. be able to.

  The present invention can be suitably used for various pneumatic radial tires including passenger vehicle tires. Moreover, it is not limited to a tire, It can use as a reinforcing material of various rubber products.

7 ... Belt, 7A, 7B ... Belt ply, 10 ... Steel cord, 12 ... Main filament, 13 ... Main filament bundle, 14 ... Wrapping material

Claims (4)

A steel cord in which a wrapping material is wound around a bundle of main filaments arranged in a line without twisting a plurality of metal filaments, and the wrapping material is impregnated with a curable resin on a nonmetallic fiber and cured. Monodea Ru, there is provided a method of manufacturing a steel cord for rubber reinforcement,
Using a mold having a flat cross-sectional shape corresponding to the main filament bundle, a non-metallic fiber impregnated with a curable resin, which is an epoxy resin composition in which crosslinked rubber particles are blended with an epoxy resin, is wound around the mold Then, the wrapping material is molded by heating and curing the curable resin, and after the molded wrapping material is removed from the mold, it is wound around the aligned main filament bundles.
Manufacturing method of steel cord for rubber reinforcement. The method for producing a steel cord for rubber reinforcement according to claim 1, wherein the non-metallic fiber has a tensile strength of 2000 MPa or more. The non-metallic fiber is at least one selected from the group consisting of aramid fiber, wholly aromatic polyester fiber, polyparaphenylene benzoxazole fiber, polyvinyl alcohol fiber, carbon fiber, and glass fiber. Item 3. A method for producing a steel cord for reinforcing rubber according to Item 1 or 2. To prepare a rubber-reinforcing steel cord by the method according to any one of claims 1 to 3 the pneumatic tire manufacturing method for manufacturing a pneumatic tire using the rubber reinforcing steel cord belt ply.

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