JP5438362B2 - Rubber-steel cord composite and pneumatic radial tire - Google Patents

Description

  The present invention relates to a rubber-steel cord composite used as a reinforcing member for a pneumatic radial tire, and a pneumatic radial tire having a reinforcing layer formed by the rubber-steel cord composite.

  Since cords used to reinforce pneumatic radial tires are required to have high strength, cords in which a plurality of sheath filaments are twisted on a core filament and core strands in which a plurality of filaments are twisted are further added. A cord having a so-called layer twist structure in which a plurality of sheath strands are twisted together is used. These cords are aligned and coated with a sheet-like coating rubber to obtain a rubber-cord composite.

  Such a coating rubber contains an adhesion promoter component for promoting adhesion to a cord such as steel and a large amount of sulfur. As such an adhesion promoter, organic acid cobalt salt is typical, but if it is blended in a large amount, it reacts with a vulcanization accelerator, an anti-aging agent, etc., so that it can be left in an unvulcanized state and then adherence or rubber. There is a possibility that the aging resistance of the resin may decrease, and the cost increases. In addition, when a large amount of sulfur is blended, vulcanization proceeds excessively before the vulcanization step, and there may be a problem that the physical properties of rubber after vulcanization are deteriorated.

  Under such circumstances, various rubber-cord composites having a rubber layer covering the periphery of the cord have been developed in addition to the coating rubber in order to solve the above problems (see Patent Documents 1 to 3).

JP 2002-338749 A JP 2003-11613 A JP 2007-313944 A

  However, none of the rubber-cord composites can sufficiently solve the problems caused by the above adhesion promoter and high sulfur content.

  Accordingly, the present invention provides a rubber-steel cord composite capable of sufficiently reducing the adhesion promoter and sulfur content in the coating rubber while maintaining good adhesion, and a pneumatic radial tire using the rubber-steel cord composite as a reinforcing layer. The purpose is to do.

  In order to solve the above-mentioned problems, the present inventor provided a filling rubber layer and a covering rubber layer on the core, so that the adhesion promoter and sulfur migrated from the covering rubber to the filling rubber or to the coating rubber during vulcanization. Focusing on this phenomenon, the present inventors have found a rubber-steel cord composite utilizing this phenomenon and completed the present invention.

That is, the rubber-steel cord composite of the present invention is provided around one or a plurality of core filaments or core strands, and around the core formed by coating or loading the filler rubber (A) in the gap.
A plurality of sheath filaments or sheath strands are twisted together to form a layer-twisted steel cord or a double-stranded steel cord,
A rubber-steel cord composite obtained by coating the outer surface of the layer-twisted steel cord or the double-twisted steel cord with a coating rubber (B) containing an adhesion promoter and further coating the coating rubber (C),
The content of the adhesion promoter in the coated rubber (B) is larger than the content of the adhesion promoter in the filled rubber (A) and the content of the adhesion promoter in the coating rubber (C).
It is desirable that the filling rubber (A) and / or the coating rubber (C) does not contain an adhesion promoter.

Further, the covering rubber (B), the filling rubber (A) and / or the coating rubber (C) contains sulfur, and the sulfur content in the filling rubber (A) and / or the coating rubber (C) is The content of sulfur in the coated rubber (B) is preferably less.
The pneumatic radial tire of the present invention has a reinforcing layer made of these rubber-steel cord composites.

According to the rubber-steel cord composite of the present invention, since the content of the adhesion promoter in the coating rubber (C) is reduced as much as possible, the cost can be reduced and the aging resistance of the coating rubber (C) can be reduced. It can be effectively prevented.
In addition, since the filled rubber (A) and the coated rubber (B) exist in the core, the contact area between the filament or strand in the core and the rubber can be increased, and a stronger and more durable bond is possible. It becomes.

Furthermore, the sulfur content in the coating rubber (C) can also be effectively reduced, and it is possible to prevent a decrease in fatigue fracture resistance.
If such a rubber-steel cord composite of the present invention is employed as a reinforcing layer, a pneumatic radial tire excellent in durability can be realized.

It is a figure which shows the layer twist steel cord which twisted together the filament of the same diameter of 3 + 9 structure. It is a figure which shows the double twist steel cord which twisted together the strand of the same diameter of 3 + 9 structure. FIG. 3A is a schematic view showing a rubber-steel cord composite of the present invention, and FIG. 3B is a schematic view showing a conventional rubber-steel cord composite. It is a figure shown about the common code | cord | chord manufacturing equipment used in order to manufacture the code | cord | chord used for this invention. It is a figure which shows the area A of the clearance gap between a core and a sheath, and the area B of the filling rubber (A) layer which occupies between a core and a sheath. It is a figure which shows a mode that a filling rubber (A) is coat | covered to a core filament using a rubber coating apparatus. It is a figure shown about the cord manufacturing equipment used in order to manufacture a double twist steel cord. It is a figure which shows the apparatus used for evaluation of corrosion fatigue resistance.

  Hereinafter, the present invention will be described in detail with reference to the drawings as necessary. FIG. 1 shows a cross section orthogonal to the axial direction of a cord according to the present invention.

  FIG. 1 shows a steel cord used for the rubber-steel cord composite of the present invention, and nine sheaths that become sheaths 2 around a core 1 composed of three core filaments (or core strands) 1a. This is a layer-twisted steel cord 3a in which filaments (or strands) of the same diameter formed by twisting filaments (or sheath strands) 2a are twisted. The layer-twisted steel cord 3a has a filled rubber (A) layer 4 between the core 1 and the sheath 2 as shown by the oblique lines in FIG. In addition, when using a core strand and a sheath strand, as shown to Fig.2 (a)-(c), the double twisted steel cord 3b is comprised by twisting together several strands. FIG. 2 (a) has a rubber (A) layer 4 around the core strand 5, and FIG. 2 (b) is a result of twisting a plurality of steel cords as shown in FIG. 2 (c) is formed by twisting a plurality of steel cords as shown in FIG. 1 and further coating with a filled rubber (A).

  The rubber-steel cord composite of the present invention has a plurality of sheath filaments around the core formed by coating or loading the filler rubber (A) around and around the plurality of core filaments (or core strands). (Or sheath strand) is twisted to form a layer-twisted steel cord (or double-twisted steel cord), and the outer surface of the steel cord is coated with the coating rubber (B), and further coated with the coating rubber (C). It becomes. That is, as shown in the schematic diagram of FIG. 3A, the rubber layer is a rubber-steel cord composite composed of three layers of a filled rubber (A), a covering rubber (B), and a coating rubber (C). In the conventional rubber-steel cord composite, for example, as shown in FIG. 3B, the filler rubber (A) is not coated or loaded around the core filament (or core strand) and in the gap. It was. On the other hand, since the rubber-steel cord composite of the present invention is formed by coating or loading the filled rubber (A) and the coated rubber (B) as described above, the filament (or core strand) is filled with the filled rubber (A). ) And the covering rubber (B) are in direct contact with each other, and it is possible to realize stronger adhesion and higher durability than the case of the covering rubber (B) alone. Further, the presence of the filled rubber (A) suppresses fretting and improves corrosion fatigue resistance.

  The filled rubber (A) only needs to be filled in at least a part of the periphery and gaps of the plurality of core filaments (or core strands), and does not necessarily reach the outer surface of the core filament (or core strand). It does not have to protrude. In addition, FIG. 2 shows an embodiment in which the filler rubber (A) is not coated or loaded around and between the core filaments forming the core strand. It may be coated or loaded.

  Steel for forming the cord used in the present invention is not particularly limited, but it is brass-coated by using a usual method, for example, a plating method, various CVD methods, a PVD method, etc., and has an adhesive property with vulcanized rubber. Particularly preferred are raised filaments (or strands).

  The rubber component used in the filling rubber (A), the covering rubber (B) and the coating rubber (C) is not particularly limited as long as it is used for tires. For example, natural rubber (NR) or polybutadiene is used. Rubber (BR), styrene / butadiene copolymer rubber (SBR), styrene / isoprene copolymer rubber (SIR), polyisoprene rubber (IR), butyl rubber (IIR), acrylonitrile-butadiene rubber, chloroprene rubber and ethylene / propylene Synthetic rubbers such as copolymers may be mentioned, but it is desirable to use natural rubber (NR) alone.

  In addition to the rubber components, additives, adhesion promoters, and the like are appropriately blended according to the properties required for each of the filled rubber (A), the coated rubber (B), and the coated rubber (C).

  Examples of the additive include a filler. In addition to carbon black such as SRF, GPF, FER, HAF, and ISAF, silica, calcium carbonate, talc, and the like can be used. When carbon black is blended, it is desirable to blend in an amount of 40 to 60 parts by mass with respect to 100 parts by mass of the rubber component.

  Examples of the adhesion promoter include organic acid cobalt salts such as cobalt naphthenate, cobalt rosinate, and linear or branched monocarboxylic acid cobalt salts having about 5 to 20 carbon atoms.

As other additives, a vulcanizing agent such as sulfur, an anti-aging agent, a vulcanization accelerator, a processing aid such as zinc oxide, an ozone deterioration preventing agent, and a plasticizer can be blended.
Hereinafter, the specific compositions of various filled rubbers (A), coated rubbers (B) and coating rubbers (C) in the rubber-steel cord composite of the present invention will be described.

<< Filled rubber (A) >>
In the rubber-steel cord composite of the present invention, the content of the adhesion promoter in the filled rubber (A) is less than the content of the adhesion promoter in the coated rubber (B) described later. Furthermore, it is desirable that the content of the adhesion promoter in the coating rubber (C) is larger, but it is more desirable not to contain the adhesion promoter. Specifically, it is usually less than 5.0 parts by mass, preferably less than 0.5 parts by mass with respect to 100 parts by mass of the rubber component. Thus, even if the content of the adhesion promoter in the filled rubber (A) is reduced, the adhesion promoter diffuses and transfers from the coated rubber (B) during vulcanization, so that sufficient adhesiveness is sufficiently maintained. can do. In addition, by setting the amount within the above range, the reaction with the vulcanization accelerator and anti-aging agent blended in the coating rubber (C) can be effectively reduced, and the adhesiveness and aging resistance are lowered. Can be suppressed. In addition, it can greatly contribute to cost reduction. Furthermore, the freedom degree of the compounding design regarding an adhesion promoter including coating rubber (C) and covering rubber (B) improves.

  Moreover, when mix | blending sulfur with the said filling rubber (A), both content of this sulfur and content of sulfur in coating rubber (C), or at least one content is in coating rubber (B). Desirably less than the sulfur content. Specifically, the amount is usually 3.0 to 7.0 parts by mass, preferably 3.0 to 5.0 parts by mass with respect to 100 parts by mass of the rubber component. In this way, even if the sulfur content in the filled rubber (A) is reduced, sulfur diffuses and migrates from the coated rubber (B) during vulcanization, so that sufficient adhesiveness is fully exhibited. Can do. As a result, the progress of vulcanization before vulcanization can be more effectively suppressed, which contributes to improved workability.

<< Coating rubber (B) >>
The content of the adhesion promoter in the coated rubber (B) is larger than the content of the adhesion promoter in the filled rubber (A) and the content of the adhesion promoter in the coating rubber (C) described later. That is, the content of the adhesion promoter in the coated rubber (B) layer is the largest among the filled rubber (A) layer, the coated rubber (B) layer, and the coated rubber (C) layer. Specifically, it is 1.0-5.0 mass parts normally with respect to 100 mass parts of rubber components, Preferably it is 3.0-5.0 mass parts. If the amount is not less than the above lower limit value, even if the adhesion promoter diffuses and transfers to the coating rubber (C) or the filled rubber (A) after vulcanization, the adhesion promoter remains in a sufficient amount in the coating rubber (B). In addition, while maintaining excellent oxygen-degrading adhesiveness with the steel cord, there is no fear that the initial adhesiveness will be unnecessarily lowered. On the other hand, when it mixes exceeding the said upper limit, it is difficult to acquire the remarkable adhesion promotion effect, and there exists a possibility that oxygen deterioration adhesiveness may become inadequate while causing a cost increase. As described above, when the adhesion promoter is contained, the coated rubber (B) is in direct contact with the steel cord. When the filling rubber (A) contains the adhesion promoter, the bonding area between the steel cord and the rubber is combined with this. Can be ensured moderately and contribute to the improvement of corrosion fatigue resistance.

  In addition, when sulfur is added to the coated rubber (B), the sulfur content is preferably larger than the sulfur content in the filled rubber (A) and / or the coating rubber (C). Specifically, the amount is usually 3.0 to 7.0 parts by mass, preferably 5.0 to 7.0 parts by mass with respect to 100 parts by mass of the rubber component. If the amount is not less than the above lower limit, even if sulfur diffuses and transfers to the coating rubber (C) or filled rubber (A) during vulcanization, a sufficient amount of sulfur remains in the coating rubber (B). It is possible to effectively exhibit excellent adhesiveness with the steel cord. On the other hand, when it mix | blends exceeding the said upper limit, there exists a possibility that fatigue fracture resistance may fall. At this time, it is desirable that the content of sulfur in the coating rubber (C) and the content of sulfur in the filled rubber (A) are both higher or higher than one content. In this case, the progress of vulcanization before vulcanization can be more effectively suppressed, which can contribute to improvement in workability.

<< Coating rubber (C) >>
The content of the adhesion promoter in the coating rubber (C) used in the present invention is desirably less than the content of the adhesion promoter in the filled rubber (A), and more desirably not contained. Specifically, the amount is usually less than 1.0 part by mass, preferably less than 0.5 part by mass with respect to 100 parts by mass of the rubber component. Thus, even if the content of the adhesion promoter in the coating rubber (C) is reduced, the adhesion promoter diffuses and transfers from the filled rubber (A) or the coating rubber (B) during vulcanization. Adhesiveness can be sufficiently maintained. In addition, by setting the amount within the above range, the reaction with the vulcanization accelerator and anti-aging agent blended in the coating rubber (C) can be effectively reduced, and the adhesiveness and aging resistance are lowered. Can be suppressed. In addition, it can greatly contribute to cost reduction. Furthermore, the freedom degree of the compounding design regarding an adhesion promoter including the said filling rubber (A) and covering rubber | gum (B) improves.

  Moreover, when mix | blending sulfur with the said coating rubber (C), both content of this sulfur and content of sulfur in a filling rubber (A), or at least one content is in coating rubber (B). Desirably less than the sulfur content. Specifically, the amount is usually 3.0 to 7.0 parts by mass, preferably 3.0 to 5.0 parts by mass with respect to 100 parts by mass of the rubber component. Thus, even if the content of sulfur in the coating rubber (C) is reduced, sulfur diffuses and migrates from the coating rubber (B) during vulcanization, so that sufficient adhesiveness can be sufficiently exhibited. Can do. As a result, the progress of vulcanization before vulcanization can be more effectively suppressed, which contributes to improved workability.

[Method for producing rubber-steel cord composite]
First, the rubber-steel cord composite of the present invention is manufactured by a cord manufacturing facility shown in FIG. Such a cord manufacturing facility is provided with a predetermined number of core unwinding portions 9 for unwinding a core portion 9a formed by twisting a plurality of core filaments and sheath unwinding portions 10 for unwinding a sheath filament 10a. There are provided a wire concentrator 11 for converging the filaments unwound from the outlet and a twisting machine 12 for twisting the converging filaments. And between the core unwinding part 9 and the wire concentrator 11, the rubber | gum coating apparatus 13 which coat | covers the unvulcanized filling rubber (A) to the core part 9a is installed.

  Next, in the method of manufacturing a cord with the above-described cord manufacturing facility, first, the core portion 9a wound around the core unwinding portion 9 is unwound and guided to the rubber coating device 13 side. The portion 9a is covered with the filled rubber (A) to form a rubber-coated filament 13a. Next, the rubber-coated filament 13a is supplied to the wire concentrator 11 installed on the entry side of the stranding machine 12, and is unwound from the sheath unwinding portion 10 around the rubber-coated filament 13a by the wire concentrator 11. The sheath filament 10a is converged to form a converging filament 11a, and the converging filament 11a is supplied to the stranding machine 12. After that, the cord 15 is formed by twisting the converging filaments 11 a with the stranded wire machine 12.

  Here, it is desirable that the core portion 9 a unwound from the core unwinding portion 9 is coated with a predetermined amount of filled rubber (A) as described below, and then supplied to the stranding machine 12. That is, by providing a predetermined amount of the filled rubber (A) layer 4, it is possible to prevent the filled rubber (A) from protruding more than necessary from between the sheath filaments constituting the twisted cords, and at an appropriate amount of the core Filling rubber (A) is loaded into the gap between the portions 9a. The predetermined amount in the filled rubber (A) is, in a cross section orthogonal to the axial direction of the cord, the area A of the gap between the core and the sheath and the area B of the filled rubber (A) layer occupied between the core and the sheath, An amount that satisfies the relationship of A ≦ B ≦ 10A.

  The area A of the gap between the core and the sheath is defined with reference to the closed cord. For example, as shown in FIG. 5A, a closed cord having the same structure as that shown in FIG. 1 has an area A {dotted line portion in FIG. 5) as a gap between the core and the sheath in a cross section orthogonal to the axial direction of the closed structure cord. . However, the gap between the sheaths 28 where the core 27 is not interposed is excluded.

  Further, the area B of the filled rubber (A) layer 4 occupying between the core 27 and the sheath 28 is a rubber portion (vertical line portion) covered around the core as shown in FIG. Here, in forming the cord shown in FIG. 1, in order to form the filled rubber (A) layer 4 that is 1 to 10 times the area A, the area B corresponds to the area B as shown in FIG. After covering the core filament with the filled rubber (A), the sheath filament may be twisted together.

  Furthermore, the rubber coating apparatus 13 for covering the core 9a with the filled rubber (A) includes, for example, a rubber extruder 16 and a rubber extrusion head 18 as shown in FIG. Here, as shown in FIG. 6, the rubber coating device 13 has a rubber extrusion screw 17 from the rubber extruder 16 side through the rubber extrusion screw 17 to the rubber extrusion head portion 18, as shown inside the rubber extruder 16 and the rubber extrusion head portion 18. 19 is extruded to fill the rubber extrusion head portion 18 with the filled rubber (A). Next, when the core portion 9a is supplied into the rubber extrusion head portion 18 from the cord guide 20 installed on the entry side of the rubber extrusion head portion 18, and passed through the rubber extrusion head portion 18, the peripheral surface of the core portion 9a. The filled rubber (A) 19 is coated. Thereafter, the core 9a coated with the filled rubber (A) 19 is passed through the base 21 installed on the exit side of the rubber extrusion head 18, and the rubber extrusion head 18 is adjusted while the thickness of the coated rubber (B) is adjusted. It is led out and becomes a filled rubber (A) coated filament 13a.

  In the present invention, when the core portion 9a is coated with the filled rubber (A) by the rubber coating apparatus 13, a plurality of core filaments are coated at the same time. May be.

  Thereafter, the coated rubber (B) is coated in the same manner, the obtained plural cords are arranged in parallel at intervals of 1.5 to 2.0 mm, and the coated rubber (C) is coated from above and below to obtain a desired A rubber-steel cord composite is obtained by cutting into a width and an angle corresponding to the part.

FIG. 7 shows an example of a production facility used particularly when producing a double stranded steel cord. In this cord facility, a core strand unwinding portion 50 for unwinding the core strand 50a is installed, and the unvulcanized filled rubber (A) is cored between the core strand unwinding portion 50 and the sheath strand unwinding portion 55. A rubber coating device 53 including a rubber extruder 51 and a rubber extrusion head unit 52 for coating the strand 50a is installed.
Next, the core strand 50a guided from the rubber extrusion head portion 52 of the rubber coating device 52 is supplied to the sheath strand unwinding portion 55 installed for unwinding the sheath strand 55a on the other side, and the straightening jig 56 is connected to the straightness correcting jig 56. The double twisted cord 57 a is formed while being routed, and the double twisted cord winding portion 57 is transferred. Thereafter, the coated rubber (B) and the coated rubber (C) are coated in the same manner as described above to obtain a rubber-steel cord composite.

[Pneumatic radial tire]
By adopting the rubber-steel cord composite of the present invention as a reinforcing layer for a belt layer, a carcass layer, or a bead portion of a pneumatic radial tire, adhesion durability, aging resistance, and fatigue fracture resistance in the reinforcing layer Thus, a high-performance pneumatic radial tire having excellent durability can be realized while reducing costs.

  It is also possible to improve the productivity and handleability of layer-twisted steel cords and double-twisted steel cords, and to achieve more efficient production of rubber-steel cord composites and pneumatic radial tires.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples.

[Examples 1 to 4 , Examples 7 to 11, Comparative Example 1 ]
A rubber was produced according to the composition shown in Table 2, and a steel cord and a rubber-steel cord composite of the embodiment shown in the schematic diagram of FIG. 3A were produced and evaluated according to the following evaluation contents. In addition, as a comparative example 1, a conventional rubber-steel cord composite in which a steel cord is only coated with a coating rubber (C) as shown in the schematic diagram of FIG. A steel cord coated only with the covering rubber (B) was produced. The results are shown in Table 3.

<Initial adhesiveness>
The steel cords of 3 + 9 × 0.22 mm shown in FIG. 1 are arranged in parallel at intervals of 1.5 mm, and each rubber composition is coated from the top and bottom of the steel cord, and this is vulcanized at 145 ° C. for 15 minutes to obtain a sample. Produced. The sample was allowed to stand at room temperature for 1 hour, and then the steel cord was pulled out and its rubber coverage was visually evaluated according to the evaluation criteria shown in Table 1.

<Oxygen degradation adhesiveness>
The steel cords of 3 + 9 × 0.22 mm shown in FIG. 1 are arranged in parallel at 1.5 mm intervals, coated from the top and bottom of the steel cords using each rubber composition, and this is vulcanized at 145 ° C. for 40 minutes to prepare a sample. Produced. The sample was allowed to stand at an oxygen partial pressure of 0.03 MPa at a temperature of 55 ° C. and a humidity of 80% for 3 days, and then the steel cord was pulled out. It was evaluated by.

<< Evaluation of corrosion fatigue resistance >>
The steel cords of 3 + 9 × 0.22 mm shown in FIG. 1 were arranged in parallel at intervals of 1.5 mm, and each rubber composition was coated from the top and bottom of the steel cord, and vulcanized at 145 ° C. for 40 minutes. Next, a bundle of three steel cords (upper gauge: 1.0 mm, lower gauge: 2.0 mm, total gauge: 3.9 mm, cord pitch: 1.5 mm) was cut out as a sample and immersed in warm water at 70 ° C. for 12 hours. I let you. Thereafter, using the apparatus as shown in FIG. 8, each sample 30 is passed through a pulley 31 (diameter 22 mm), and the sample 30 is driven in the vertical X direction with a cord strength of 7.0% applied. The number of repetitions until rupture of was measured. About the obtained result, the control example was set to 100 and indicated as an index. Higher values indicate higher corrosion fatigue resistance.

<Cost Evaluation>
The cost when producing rubber-steel cord composites of the same size was evaluated in four stages of ◎, ○, Δ, and × in ascending order.

According to the results in Table 3, the examples using the filled rubber (A) are superior in oxygen deterioration adhesion and corrosion fatigue resistance to the control example and the comparative example without the filled rubber (A), and the cost can be reduced. It can be seen that it can be effectively realized.
In particular, according to Examples 1 to 4 and 7 to 11, the coating rubber (C) does not contain an adhesion promoter, but the coating rubber (B) has a high content of the adhesion promoter, so that the control example and It is clear that excellent corrosion fatigue resistance can be exhibited and effective cost reduction can be achieved while maintaining the same adhesion performance as that of Comparative Example 1.

  In Examples 7 and 10-11, in which the sulfur content in the filled rubber (A) is less than the sulfur content in the coated rubber (B), the vulcanization progress before the vulcanization step is effectively performed. The workability was very good.

DESCRIPTION OF SYMBOLS 1 Core 1a Core filament 2 Sheath 2a Sheath filament 3a Layer twisted cord 3b Double twisted cord 4 Filled rubber (A) layer 5 Core strand 6 Sheath strand 7 Coating rubber (C) layer 8 Cover rubber (B) layer 9 Core unwinding part 9a Core part 10 Sheath unwinding part 10a Sheath filament 11 Wire concentrator 11a Converging filament 12 Stranding machine 13 Rubber coating device 13a Rubber coating filament 15 Code 16 Rubber extrusion machine 17 Rubber extrusion screw 18 Rubber extrusion head part 19 Filling rubber (A )
20 Code Guide 21 Base 27 Core 28 Sheath 30 Sample 31 Pulley 32 Chuck 50 Core Strand Unwinding Portion 50a Core Strand 51 Rubber Extruder 52 Rubber Extrusion Head Portion 53 Rubber Coating Device 55 Sheath Strand Unwinding Portion 55a Sheath Strand 56 Straight Straightening Jig 57 Double twisted cord winding part 57a Double twisted steel cord

Claims (4)

Around one or a plurality of core filaments or core strands and around the core formed by coating or loading the filler rubber (A) in the gap,
A plurality of sheath filaments or sheath strands are twisted together to form a layer-twisted steel cord or a double-stranded steel cord,
A rubber-steel cord composite obtained by coating the outer surface of the layer-twisted steel cord or the double-twisted steel cord with a coating rubber (B) containing an adhesion promoter and further coating the coating rubber (C),
Rubber-steel characterized in that the content of the adhesion promoter in the coated rubber (B) is higher than the content of the adhesion promoter in the filled rubber (A) and the content of the adhesion promoter in the coating rubber (C) Code complex.   The rubber-steel cord composite according to claim 1, wherein the filling rubber (A) and / or the coating rubber (C) does not contain an adhesion promoter.   The covering rubber (B), the filling rubber (A) and / or the coating rubber (C) contains sulfur, and the sulfur content in the filling rubber (A) and / or the coating rubber (C) is The rubber-steel cord composite according to claim 1 or 2, wherein the content of the rubber is less than the content of sulfur in the coated rubber (B).   A pneumatic radial tire having a reinforcing layer made of the rubber-steel cord composite according to any one of claims 1 to 3.

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