CN115244246B

CN115244246B - Rubber composite, tire, and steel cord

Info

Publication number: CN115244246B
Application number: CN202080098104.4A
Authority: CN
Inventors: 中岛彻也; 松冈映史; 真岛正利; 小川光靖; 神田良子; 境田英彰
Original assignee: Sumitomo Electric Industries Ltd
Current assignee: Sumitomo Electric Industries Ltd
Priority date: 2020-03-13
Filing date: 2020-12-23
Publication date: 2024-04-09
Anticipated expiration: 2040-12-23
Also published as: DE112020006889T5; WO2021181821A1; CN115244246A; JPWO2021181821A1

Abstract

A rubber composite comprises a steel cord and rubber covering at least a part of the surface of the steel cord, wherein a first covering containing Cu is disposed on the end surface of the steel cord in the longitudinal direction.

Description

Rubber composite, tire, and steel cord

Technical Field

The present disclosure relates to rubber composites, tires, steel cords.

The present application claims that the entire contents of the descriptions in japanese patent application 2020-044547 are incorporated by reference based on the priority of japanese patent application No. 2020-044547 applied at 3/13 in 2020.

Background

For example, patent document 1 discloses that a predetermined brass plating is applied to the surface of a steel wire constituting a steel cord in a pneumatic steel radial tire having a carcass layer composed of a steel cord in which the steel cord is buried.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 8-253004

Disclosure of Invention

The rubber composite of the present disclosure has:

steel cord, and

rubber covering at least a portion of the surface of the steel cord, and

a first coating including Cu is disposed on the end surface in the longitudinal direction of the steel cord.

Drawings

Fig. 1 is a perspective view of a rubber composite according to an embodiment of the present disclosure.

Fig. 2 is a cross-sectional view taken along line A-A' of fig. 1.

Fig. 3 is an explanatory diagram of a method of calculating a coverage ratio of an end face in a longitudinal direction of a steel cord caused by a covering.

Fig. 4 is a cross-sectional view of a tire according to an embodiment of the present disclosure.

Fig. 5 is a cross-sectional view of a steel cord according to one embodiment of the present disclosure.

Detailed Description

[ problem to be solved by the present disclosure ]

In products such as tires, which contain rubber composites, corrosion may occur near the end surfaces of the steel cords. In recent years, in order to suppress the frequency of replacement of products including rubber composites, etc., improvement in durability has been demanded. Therefore, it is required to suppress corrosion in the vicinity of the end face of the steel cord.

Accordingly, an object is to provide a rubber composite in which corrosion of an end face of a steel cord is suppressed.

[ Effect of the present disclosure ]

According to the present disclosure, a rubber composite in which corrosion of the end face of a steel cord is suppressed can be provided.

[ description of embodiments of the disclosure ]

First, embodiments of the present disclosure are listed and described. In the following description, the same or corresponding elements are denoted by the same reference numerals, and the same description is not repeated.

(1) The rubber composite according to one embodiment of the present disclosure includes:

steel cord, and

rubber covering at least a portion of the surface of the steel cord, and

The rubber composite according to one embodiment of the present disclosure can improve the corrosion resistance of the end surface of the steel cord by providing the first cover on the end surface in the longitudinal direction of the steel cord.

The first coating contains Cu (copper), thereby protecting the surface (specifically, the end surface in the longitudinal direction) of the steel cord and improving corrosion resistance.

(2) The first cover may further comprise S.

S (sulfur) is also contained in the first coating to form Cu with the Cu ₂ The copper-sulfur compound such as S can protect the end face of the steel cord in the longitudinal direction, and can improve corrosion resistance. In addition, in the case where the steel cord and the rubber are bonded via the first covering, cu ₂ The copper-sulfur compound such as S can improve the adhesion between the steel cord and the rubber, and can particularly improve the durability of the rubber composite.

(3) The first cover may further comprise Zn.

Zn (zinc) promotes the reaction of Cu with other elements contained in the rubber, promoting Cu ₂ And S and other copper compounds. The copper compound can protect the end face of the steel cord in the longitudinal direction in particular, and further improve the corrosion resistance. In addition, when the steel cord and the rubber are bonded to each other through the first cover, the copper compound improves the adhesion between the steel cord and the rubber, and improves the durability of the rubber composite.

(4) The first cover may further contain one or more selected from Sn, cr, fe, co and Ni.

Sn (tin), cr (chromium), fe (iron), co (cobalt), ni (nickel) have a greater ionization tendency than Zn. Therefore, the first coating layer can function as sacrificial corrosion protection or can increase the synthesis potential (the synthesis potential) of Cu and Zn by further including one or more selected from Sn, cr, fe, co and Ni in addition to Cu and Zn. Therefore, the end face in the longitudinal direction of the steel cord can be particularly protected, and the corrosion resistance can be further improved.

(5) The end face of the steel cord may also be covered with the rubber via the first cover.

The end surface in the longitudinal direction of the steel cord is covered with rubber via the first cover, whereby the end surface in the longitudinal direction of the steel cord can be protected by rubber in addition to the first cover. Therefore, the corrosion resistance of the end surface in the longitudinal direction of the steel cord can be improved. In addition, breakage of the rubber composite can be suppressed, and durability can be improved.

(6) The end face of the steel cord may be bonded to the rubber via the first cover.

The end surface in the longitudinal direction of the steel cord is bonded to the rubber through the first cover, whereby the end surface in the longitudinal direction of the steel cord can be protected by the rubber in addition to the first cover. Therefore, the corrosion resistance of the end surface in the longitudinal direction of the steel cord can be improved.

In addition, when the rubber composite is applied to a tire or the like, a large force is easily applied near the boundary line between the end surface of the steel cord in the longitudinal direction and the rubber. However, by bonding the end surface in the longitudinal direction of the steel cord to the rubber via the first cover, the rubber, the first cover, and the steel cord are integrated, and the applied force can be supported. Therefore, breakage of the rubber composite is suppressed in particular, and durability can be improved.

In addition, by bonding the end face in the longitudinal direction of the steel cord, the first cover, and the rubber, it is possible to prevent foreign matter such as water from entering between the members in particular. Therefore, penetration of foreign matter such as water into the end face of the steel cord can be suppressed, and in particular, corrosion resistance can be improved.

(7) The first cover may cover more than 20% of the end face.

The corrosion resistance of the end face of the steel cord 11 can be particularly improved by covering the end face area of the steel cord 11 in the longitudinal direction by 20% or more of the end face area.

(8) A second covering comprising Cu may be arranged on the side of the steel cord.

By providing the rubber composite with the second cover on the side surface of the steel cord, the corrosion resistance of the side surface of the steel cord can be improved.

The second coating contains Cu, thereby protecting the surface (specifically, the side surface) of the steel cord and improving corrosion resistance.

(9) A tire according to one embodiment of the present disclosure includes the rubber composite of any one of (1) to (8).

A tire according to one embodiment of the present disclosure includes the rubber composite described above. Therefore, corrosion of the end face in the longitudinal direction of the steel cord can be suppressed, and durability can be improved.

(10) The steel cord according to one embodiment of the present disclosure is provided with a coating film containing Cu on the end surface in the longitudinal direction.

The steel cord according to one embodiment of the present disclosure has a coating film on the end surface in the longitudinal direction, thereby improving the corrosion resistance of the end surface.

The coating film contains Cu (copper), thereby protecting the surface of the steel cord and improving corrosion resistance.

(11) The coating film may further contain Zn.

Zn has a greater ionization tendency than Cu. Therefore, the coating film can function as sacrificial corrosion protection by containing Zn in addition to Cu. Therefore, the end face in the longitudinal direction of the steel cord can be particularly protected, and the corrosion resistance can be further improved.

(12) The coating film may further contain one or more selected from Sn, cr, fe, co and Ni.

Sn, cr, fe, co, ni has a greater ionization tendency than Zn. Therefore, the coating film can function as sacrificial corrosion protection or can increase the synthetic potential of Cu and Zn by containing one or more selected from Sn, cr, fe, co and Ni in addition to Cu and Zn. Therefore, the end face in the longitudinal direction of the steel cord can be particularly protected, and the corrosion resistance can be further improved.

(13) The coating may cover 20% or more of the end face.

The coating covers 20% or more of the end surface area in the longitudinal direction of the steel cord 11, thereby particularly improving the corrosion resistance of the end surface of the steel cord.

Detailed description of embodiments of the disclosure

Hereinafter, specific examples of a rubber composite, a tire, and a steel cord according to an embodiment of the present disclosure (hereinafter referred to as "the present embodiment") will be described with reference to the drawings. It is to be understood that the invention is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[ rubber Complex ]

In products such as tires, which contain rubber composites, corrosion may occur near the end surfaces of the steel cords. In order to suppress the occurrence of such corrosion, the inventors of the present invention have studied the cause of the occurrence of corrosion.

As described above, a coating film obtained by plating has been conventionally formed on the surface of a wire rod of a steel cord.

When a rubber composite is produced using a steel cord having a coating film, a metal component of the coating film of the steel cord reacts with a rubber component to form a coating, also called an adhesive layer, on the surface of the steel cord. It is considered that by forming the cover on the surface of the steel cord, the steel cord is protected and corrosion resistance is improved.

However, in manufacturing the rubber composite, it is necessary to cut the steel cord in accordance with the size of the rubber composite. Therefore, the end face of the steel cord contained in the rubber composite is exposed to the wire, and no covering is formed on the end face of the steel cord. As a result, in the conventional rubber composite, it is considered that the end face of the steel cord is not protected and corrosion occurs at the end face.

Based on the above-described results, the inventors of the present invention completed the rubber composite of the present embodiment, which can suppress corrosion at the end face of the steel cord.

Fig. 1 and 2 show an example of the structure of the rubber composite according to the present embodiment. Fig. 1 is a perspective view of a rubber composite 10 according to the present embodiment, and fig. 2 is a cross-sectional view taken along line A-A' of fig. 1, specifically, a cross-sectional view taken along a plane passing through the center axis of the steel cord 11 at the end in the longitudinal direction of the steel cord 11. In fig. 1 and 2, the Y-axis direction is a direction parallel to the longitudinal direction of the steel cord 11, and the XZ plane is a plane perpendicular to the longitudinal direction of the steel cord 11. In fig. 1 and 2, the X-axis direction is the width direction of the rubber composite 10, and a plurality of steel cords 11 are aligned in a row along the X-axis direction. The Z-axis direction is the thickness direction of the rubber composite 10.

As shown in fig. 1, the rubber composite 10 of the present embodiment may have a steel cord 11 and a rubber 12 covering at least a part of the surface of the steel cord 11. Further, as shown in fig. 2, a first cover 131 as the cover 13 may be provided at the end face 11A in the longitudinal direction of the steel cord 11.

The number of the steel cords 11 included in the rubber composite 10 of the present embodiment is not particularly limited, and may be selected according to the application, and may be one or a plurality of, for example. In the case where the rubber composite 10 of the present embodiment includes a plurality of steel cords 11, the arrangement of the steel cords 11 is not particularly limited, and for example, as shown in fig. 1, the steel cords 11 may be arranged in a row on the XZ plane, which is a cross section perpendicular to the longitudinal direction of the plurality of steel cords 11.

Hereinafter, each member included in the rubber composite of the present embodiment will be described.

(1) Steel cord

As shown in fig. 2, the steel cord 11 may have a wire 111 and a coating film 112 covering the surface of the wire 111. Fig. 1 and 2 show an example in which the steel cord 11 is made of 1 wire, but the present invention is not limited to this embodiment. For example, a steel cord formed by twisting a plurality of steel wires may be used. When the steel cord has a structure in which a plurality of steel wires are twisted, each steel wire preferably has a wire rod 111 described below and a coating film 112 covering the surface of the wire rod 111.

The wire 111 of the steel cord 11 may be a steel wire, for example, and a high carbon steel wire may be more preferably used.

As the coating 112, the steel cord 11 may have a first coating 1121 covering the end face 11A side in addition to a second coating 1122 covering the side face 11B side of the steel cord 11.

When the rubber composite 10 is produced by providing the coating film 112 on the surface of the wire 111 of the steel cord 11, the coating 13 can be formed on the surface of the steel cord 11. Specifically, by providing the first coating 1121 covering the end face 11A side in the longitudinal direction of the steel cord 11, the first covering 131 can be formed and arranged on the end face 11A in the longitudinal direction of the steel cord 11 when the rubber composite 10 is produced.

In addition, by providing the second coating 1122 covering the side surface 11B side of the steel cord 11, the second coating 132 can be formed and arranged on the side surface 11B side of the steel cord 11 in the case of producing the rubber composite 10.

When the rubber composite 10 is produced, the first cover film 1121 and the second cover film 1122 react with the components of the rubber, and the first cover 131 and the second cover 132 can be formed. Therefore, in the case of producing the rubber composite 10, a part of the first coating 1121 and a part of the second coating 1122 may remain, or the whole may be the first coating 131 and the second coating 132. That is, the rubber composite 10 may not have the first coating 1121 and the second coating 1122.

As described above, in manufacturing the rubber composite, it is necessary to cut the steel cord in comparison with the size of the rubber composite. Therefore, in the conventional rubber composite, no coating is provided on the end face in the longitudinal direction of the steel cord. Further, it is considered that the covering is formed by reacting a rubber component with a steel cord coating component. Therefore, even when the end face in the longitudinal direction of the steel cord is not covered with a film, the end face does not form a coating, and corrosion occurs from the end face in the longitudinal direction of the steel cord in the conventional rubber composite.

On the other hand, the steel cord 11 included in the rubber composite 10 of the present embodiment has a first coating 1121 as a coating 112 on the end face 11A in the longitudinal direction. Therefore, the rubber composite 10 can have the first cover 131 on the end surface in the longitudinal direction of the steel cord 11, and can improve the corrosion resistance of the end surface 11A of the steel cord.

The steel cord 11 of the rubber composite 10 according to the present embodiment may have a second coating 1122 as the coating 112 on the side surface 11B. Therefore, the rubber composite 10 may have the second cover 132 on the side surface of the steel cord 11, and the corrosion resistance of the side surface 11B of the steel cord may be improved.

In order to manufacture the rubber composite 10, the first coating 1121 may be formed after cutting the steel cord to a predetermined length. Specifically, the steel cord 11 may be formed before being embedded in the rubber 12, or after a part of the steel cord 11 is embedded in the rubber 12 and before the end face in the longitudinal direction of the steel cord 11 is covered with the rubber 12 or the like.

The specific method of forming the first film 1121 is not particularly limited, and various methods capable of forming a film having a desired composition may be used. The first film 1121 may contain, for example, one or more selected from oxides and metals. Accordingly, the first film 1121 can be formed by various methods capable of forming oxides and metals. Examples of the method for producing the first coating 1121 include a coating method in which a coating liquid containing a predetermined component such as a metal is applied, and a dipping method in which the end face 11A side of the steel cord 11 is immersed in the coating liquid. Examples of the method for producing the first film 1121 include electroplating, electroless plating, and substitution plating. The plating method may be a brush plating method. When the first coating 1121 contains a plurality of components, a plurality of layers corresponding to the plurality of components of the first coating 1121 may be formed on the end surface of the steel cord 11 in the longitudinal direction, and the first coating 1121 may be formed by performing heat treatment as necessary. Before forming the first coating 1121, the end face 11A of the steel cord 11 is preferably subjected to a pretreatment such as degreasing to remove substances adhering to the surface, but the first coating 1121 may be formed without the pretreatment.

The method of forming the second coating 1122 is not particularly limited, and for example, a coating corresponding to the surface of a busbar for manufacturing the steel cord 11 may be formed in advance, and the busbar may be drawn, whereby the second coating 1122 may be formed on the surface of the wire 111. That is, the second coating 1122 disposed on the side 11B of the steel cord 11 is from a coating formed on the surface of the bus bar before drawing.

As described above, the first coating 1121 provided on the end face 11A side of the steel cord 11 and the second coating 1122 provided on the side face 11B side are formed at different points. Accordingly, the first film 1121 and the second film 1122 may have the same composition and film thickness, or may have different compositions and film thicknesses.

The composition of the first film 1121 and the second film 1122 as the film 112 is not particularly limited. The coating film 112 preferably contains Cu (copper), for example. In particular, it is more preferable that Zn (zinc) is further contained in addition to Cu.

Further, the coating 112 preferably further contains one or more selected from Sn (tin), cr (chromium), fe (iron), co (cobalt), and Ni (nickel) in addition to Cu and Zn.

(2) Rubber material

The rubber 12 may be produced by molding a composition of rubber and vulcanizing as needed.

The specific composition of the rubber may be selected according to the use, characteristics, etc. of the rubber composite of the present embodiment, and is not particularly limited. The rubber may contain, for example, a rubber component, sulfur and a vulcanization accelerator.

The rubber component preferably contains 60 mass% or more of one or more selected from Natural Rubber (NR) and Isoprene Rubber (IR), more preferably 70 mass% or more, and still more preferably 100 mass% or more.

This is because the fracture strength of the rubber composite can be improved by setting the proportion of at least one rubber selected from the group consisting of natural rubber and isoprene rubber in the rubber component to 60 mass% or more, which is preferable.

Examples of the rubber component used in combination with the natural rubber or the isoprene rubber include at least one selected from the group consisting of styrene-butadiene rubber (SBR), butadiene Rubber (BR), ethylene-propylene-diene rubber (EPDM), chloroprene Rubber (CR), butyl rubber (IIR), and acrylonitrile-butadiene rubber (NBR).

The sulfur is not particularly limited, and for example, sulfur generally used as a vulcanizing agent in the rubber industry can be used.

The sulfur content of the rubber is not particularly limited, and is preferably set to, for example, 5 parts by mass or more and 8 parts by mass or less with respect to 100 parts by mass of the rubber component.

This is because, by setting the ratio of sulfur to 100 parts by mass of the rubber component to 5 parts by mass or more, the crosslinking density of the obtained rubber can be increased, and in particular, the adhesion between the steel cord and the rubber can be improved. Further, this is because, by setting the ratio of sulfur to 100 parts by mass of the rubber component to 8 parts by mass or less, sulfur can be dispersed particularly uniformly in the rubber and the occurrence of blooming can be suppressed, and is preferable.

The vulcanization accelerator is not particularly limited, and for example, a sulfenamide accelerator such as N, N' -dicyclohexyl-2-benzothiazolyl sulfenamide, N-cyclohexyl-2-benzothiazolyl sulfenamide, N-t-butyl-2-benzothiazolyl sulfenamide, N-oxydiethylene-2-benzothiazolyl sulfenamide, and the like can be preferably used. In addition, thiazole accelerators such as 2-mercaptobenzothiazole and di-2-benzothiazole disulfide can be used as needed; autumn Lan M accelerators such as tetrabenzyl thiuram disulfide, tetramethyl thiuram Lan M disulfide, tetraethyl thiuram Lan M disulfide, tetra (2-ethylhexyl) thiuram disulfide, tetramethyl thiuram Lan M monosulfide, and the like.

The rubber composition used in the rubber composite of the present embodiment can be produced by kneading, heating and extruding the above-described components by a conventional method.

The rubber of the rubber composite of the present embodiment preferably contains one or more selected from the group consisting of a cobalt simple substance and a cobalt-containing compound.

Examples of the cobalt-containing compound include cobalt organic acid and cobalt inorganic acid.

As the organic acid cobalt, for example, one or more selected from cobalt naphthenate, cobalt stearate, cobalt neodecanoate, cobalt rosinate, cobalt versatate, cobalt tall oil acid and the like can be preferably used. The cobalt organic acid may be a complex salt obtained by substituting a part of the organic acid with boric acid.

As the inorganic acid cobalt, for example, one or more selected from cobalt chloride, cobalt sulfate, cobalt nitrate, cobalt phosphate and cobalt chromate can be preferably used.

In particular, the rubber of the rubber composite of the present embodiment more preferably contains cobalt organic acid. This is because the initial adhesion property between the steel cord and the rubber can be particularly improved by containing the organic acid cobalt. The initial adhesion performance means adhesion performance between the steel cord and the rubber immediately after vulcanization, for example, in the production of the rubber composite.

Further, according to the studies of the inventors of the present invention, by adding cobalt to rubber, cu in a coating can be improved ₂ The ratio of copper compound such as S, and the adhesion between the steel cord and the rubber can be improved. Further, in the case of using cobalt organic acid as the added cobalt, this tendency becomes remarkable. Therefore, the rubber of the rubber composite of the present embodiment preferably contains cobalt, particularly cobalt organic acid, and thus can be made into a rubber composite particularly excellent in durability.

In addition, the rubber may contain optional components in addition to the rubber component, sulfur, a vulcanization accelerator, cobalt, and the like. The rubber may further contain known additives for rubber such as reinforcing agents (carbon black, silica, etc.), waxes, and antioxidants.

The rubber 12 may cover at least a portion of the surface of the steel cord 11. By covering at least a part of the surface of the steel cord 11 with the rubber 12, the component of the coating 112 can react with the component of the rubber 12 to form the coating 13 even in a portion where the coating 112 is provided in a portion where the rubber 12 is not directly covered, and corrosion resistance can be improved.

Therefore, the rubber 12 may cover at least a part of the end face 11A of the steel cord 11, for example, or may cover the entire end face 11A. The rubber 12 may cover at least a part of the side surface 11B of the steel cord 11 or may cover the entire side surface 11B of the steel cord 11. The rubber 12 may also cover the entire surface of the steel cord 11.

From the viewpoint of protecting the end face 11A in the longitudinal direction of the steel cord 11, in particular, improving the corrosion resistance, the rubber 12 preferably covers at least a part of the end face 11A in the longitudinal direction of the steel cord 11, more preferably covers the entire end face 11A in the longitudinal direction of the steel cord 11.

(3) Covering material

(3-1) first cover

As described above, in the rubber composite 10 of the present embodiment, the first covering 131 as the covering 13 may be provided on the end surface 11A in the longitudinal direction of the steel cord 11.

Fig. 2 shows an example in which the first covering 131 is formed in a uniform thickness along the end face 11A in the longitudinal direction of the steel cord 11, but fig. 2 is schematically represented, not limited to this. For example, the first cover 131 may be disposed so as to be spread on the surface of the end face 11A in the longitudinal direction of the steel cord 11, or may have a film-like shape so as to cover the entire end face 11A in the longitudinal direction of the steel cord 11, as shown in fig. 2.

It is considered that the first cover 131 is formed by reacting a component contained in the first cover 1121 with a component contained in the rubber 12 or the like. Therefore, the composition of the first cover 131 varies depending on the compositions of the first cover 1121 and the rubber 12, and is not particularly limited, but the first cover 131 preferably contains Cu (copper), for example. This is because the first cover 131 contains Cu, thereby protecting the surface of the steel cord 11 (specifically, protecting the end surface in the longitudinal direction) and improving corrosion resistance.

As described above, the first film 1121 may further include Zn (zinc) in addition to Cu. The first film 1121 may contain one or more elements selected from Sn (tin), cr (chromium), fe (iron), co (cobalt), and Ni (nickel) in addition to Cu and Zn. Therefore, as for the first cover 131, zn may be further contained in addition to Cu. The first cover 131 may contain Cu and Zn, and may contain one or more selected from Sn, cr, fe, co and Ni.

In the case where the first coating film 1121 further includes Zn in addition to Cu, the first coating film 131 may further include Zn in addition to Cu. Zn promotes the reaction of Cu with other elements contained in the rubber, promoting Cu ₂ And S and other copper compounds. The copper compound protects the end face 11A of the steel cord 11 in the longitudinal direction, and can further improve corrosion resistance. In addition, when the steel cord 11 and the rubber 12 are bonded via the first cover 131, the copper compound improves the adhesion between the steel cord and the rubber, and can improve the durability of the rubber composite.

Further, sn, cr, fe, co, ni has a greater ionization tendency than Zn. Therefore, the first cover 131 can function as sacrificial corrosion protection or increase the synthetic potential of Cu and Zn by further including one or more selected from Sn, cr, fe, co and Ni in addition to Cu and Zn. Therefore, the end surface 11A in the longitudinal direction of the steel cord 11 can be protected in particular, and the corrosion resistance can be further improved.

In the production of rubber compounds, vulcanization is generally carried out. Therefore, the first cover 131 more preferably further contains S (sulfur) added at the time of vulcanization. The first cover 131 further contains S, and forms Cu with the Cu ₂ The copper-sulfur compound such as S can protect the end surface 11A of the steel cord 11 in the longitudinal direction and can improve corrosion resistance. In addition, in the case where the steel cord 11 and the rubber 12 are bonded via the first covering 131, cu ₂ The copper-sulfur compound such as S can improve the adhesion between the steel cord 11 and the rubber, and particularly improve the durability of the rubber composite.

The first cover 131 may further contain a part of the composition of the first cover 1121. As described above, the first film 1121 may contain one or more selected from an oxide and a metal. Accordingly, the first cover 131 may contain one or more kinds selected from oxides and metals from the first cover 1121. The adhesiveness to the first coating film 1121 is particularly improved by the first coating film 131 containing one or more selected from the group consisting of an oxide and a metal. Therefore, the corrosion resistance of the steel cord 11 can be particularly improved, and the adhesion force between the steel cord 11 and the rubber 12 can be improved at the portion where the steel cord 11 and the rubber 12 are adhered.

As described above, in the rubber composite 10 of the present embodiment, the rubber 12 preferably covers at least a part of the end face 11A in the longitudinal direction of the steel cord 11, and more preferably covers the entire end face 11A in the longitudinal direction of the steel cord 11.

In manufacturing the rubber composite 10, as described above, by disposing the rubber 12 so as to cover at least a part of the end face 11A in the longitudinal direction of the steel cord 11, the end face 11A in the longitudinal direction of the steel cord 11 can be bonded to the rubber 12 through the first cover 131. That is, the rubber 12, the first cover 131, and the steel cord 11 are disposed in this order from the outer surface side of the rubber composite 10 on the end surface 11A side in the longitudinal direction of the steel cord 11, and the rubber 12, the first cover 131, and the steel cord 11 can be bonded to each other.

As described above, the end face 11A in the longitudinal direction of the steel cord 11 is bonded to the rubber 12 through the first cover 131, and the end face 11A in the longitudinal direction of the steel cord 11 can be protected by the rubber 12 in addition to the first cover 131. Therefore, the corrosion resistance of the end surface 11A in the longitudinal direction of the steel cord 11 can be improved.

In addition, when the rubber composite 10 is applied to a tire or the like, a large force is easily applied near the boundary line between the end face 11A in the longitudinal direction of the steel cord 11 and the rubber 12. However, the end face 11A in the longitudinal direction of the steel cord 11 is bonded to the rubber 12 via the first cover 131, whereby the rubber 12, the first cover 131, and the steel cord 11 are integrated to support the applied force. Therefore, breakage of the rubber composite 10 is suppressed in particular, and durability can be improved.

Further, by bonding the end face 11A in the longitudinal direction of the steel cord 11, the first cover 131, and the rubber 12, it is possible to prevent foreign matter such as water from entering between the members in particular. Therefore, penetration of foreign matter such as water into the longitudinal end surface 11A of the steel cord 11 can be suppressed, and corrosion resistance can be particularly improved.

However, for example, when the rubber composite 10 is used for a long period of time, the reaction between the components of the rubber 12 and the components of the first coating 1121 may proceed, and the state of the first coating 131 and the periphery thereof may change. In addition, a force may be repeatedly applied between the rubber 12 and the steel cord 11, and a gap or the like may be generated between both members. Therefore, when the rubber composite 10 is used for a long period of time, the adhesion between the rubber 12 and the steel cord 11 may be reduced.

However, even when the adhesion between the rubber 12 and the steel cord 11 is reduced, the rubber composite 10 has an effect of protecting the end face 11A of the steel cord 11 and improving the corrosion resistance because the first cover 131 is disposed on the end face 11A of the steel cord 11.

Therefore, the end face 11A in the longitudinal direction of the steel cord 11 is not limited to the form of being bonded to the rubber 12 via the first cover 131, and the end face 11A in the longitudinal direction of the steel cord 11 may be formed of being covered with rubber via the first cover.

The end face 11A in the longitudinal direction of the steel cord 11 is covered with the rubber 12 through the first cover, and the end face 11A in the longitudinal direction of the steel cord 11 can be protected by the rubber 12 in addition to the first cover 131. Therefore, the corrosion resistance of the end surface 11A in the longitudinal direction of the steel cord 11 can be improved. In addition, breakage of the rubber composite 10 can be suppressed, and durability of the rubber composite 10 can be improved.

The case where the end face 11A in the longitudinal direction of the steel cord is covered with the rubber 12 via the first cover 131 includes the above-described adhesion and the following two modes. As the first embodiment, the rubber 12, the first cover 131, and the steel cord 11 are disposed in this order from the outer surface side of the rubber composite 10 on the end surface 11A in the longitudinal direction of the steel cord 11, and the respective members are in contact with each other. The term "contact between the members" as used herein means a state in which the members are in contact with each other without any adhesion therebetween but without any gap. As the second mode, the rubber 12, the first cover 131, and the steel cord 11 are disposed in this order from the outer surface side of the rubber composite 10 on the end surface 11A in the longitudinal direction of the steel cord 11, and a gap is included in at least a part between the respective members.

In any of the embodiments in which the end surface 11A of the steel cord 11 in the longitudinal direction is covered with rubber with the first cover 131 interposed therebetween, the first cover 1121 may be disposed on the surface of the steel cord 11 facing the first cover 131.

As described above, in the conventional rubber composite, the first coating 1121 as the coating 112 is not formed on the end face 11A side of the steel cord 11, and therefore the first coating 131 is not disposed on the end face 11A of the steel cord 11. Therefore, if the first covering 131 is disposed even in a small amount on the end face 11A of the steel cord 11, the corrosion resistance can be improved as compared with the conventional one, and the degree of disposing the first covering 131 is not particularly limited. However, the first cover 131 preferably covers 20% or more, more preferably 40% or more of the area of the end face 11A in the longitudinal direction of the steel cord 11. The first cover 131 is preferable because it covers 20% or more of the area of the end face 11A in the longitudinal direction of the steel cord 11, and thus can particularly improve the corrosion resistance of the end face 11A of the steel cord 11.

Since the first cover 131 may also cover the entire end face 11A of the steel cord 11, the first cover 131 may cover 100% or less of the area of the end face 11A of the steel cord 11.

The method of measuring the ratio of the area of the first covering 131 covering the end face 11A of the steel cord 11 is not particularly limited. For example, when the end face side rubber 121, which is a part of the rubber 12, of the rubber composite 10 disposed on the end face 11A side of the steel cord 11 is peeled off, the end face 11A side of the steel cord 11 is exposed as shown in fig. 3. Therefore, the ratio of the area occupied by the rubber 12 can be calculated, for example, by subtracting the exposed area of the steel cord 11 such as the first coating 1121 from the end surface 11A of the steel cord 11. Since the rubber 12 remaining on the end face 11A of the steel cord 11 corresponds to the portion where the first cover 131 is formed, the ratio of the area occupied by the rubber 12 can be calculated as described above, and the ratio of the area of the first cover 131 covering the end face 11A of the steel cord 11 can be calculated.

In addition, when the end face side rubber 121 is peeled off, element distribution mapping may be performed on either one of the end face side rubber 121 and the end face 11A side of the steel cord exposed after peeling off, and the ratio of the area of the first cover 131 covering the end face 11A of the steel cord 11 may be measured. When rubber remains on the end face 11A side of the steel cord, the element distribution map may be performed on the end face 11A side of the steel cord, and when rubber does not remain on the end face 11A side of the steel cord, the element distribution map may be performed on the end face side rubber 121 side.

In the element distribution mapping, a region where both the composition of the first coating film 1121 and the composition of the rubber, for example, cu and S are distributed becomes a region where the first coating 131 is formed. Therefore, from the result of the element distribution map, by obtaining the ratio of the areas where the first covers 131 are formed in the end face 11A of the steel cord 11, the ratio of the areas where the first covers 131 cover the end face 11A of the steel cord 11 can be calculated.

The method of mapping the element distribution is not particularly limited, and SEM-EDX (Scanning Electron Microscope-Energy Dispersive X-ray Spectroscope: scanning electron microscope-energy dispersive X-ray spectrometer) or the like may be used. In the case of element mapping of the end surface side rubber, since the object to be measured is an insulator, for example, low acceleration voltage SEM and EDX can be used.

(3-2) second cover

The rubber composite 10 may also have a second covering 132 as the covering 13 on the side 11B side of the steel cord 11. The second cover 132 is thought to be formed by a reaction of a component contained in the second cover 1122 with a component contained in the rubber 12 or the like. Accordingly, the composition of the second cover 132 varies depending on the composition of the second cover 1122 and the rubber 12, and is not particularly limited, but the second cover 132 preferably contains Cu (copper), for example. This is because the second coating 132 contains Cu, thereby protecting the surface (specifically, the side surface) of the steel cord 11 and improving corrosion resistance.

As described above, the second coating film 1122 may further contain Zn (zinc) in addition to Cu. Accordingly, as for the second cover 132, zn may be further contained in addition to Cu. Zn promotes the reaction of Cu with other elements contained in the rubber, and promotes Cu ₂ And S and other copper compounds. Copper compounds protect in particular the steel cords 11The side surface 11B can further improve corrosion resistance. In addition, when the steel cord 11 and the rubber 12 are bonded via the second cover 132, the copper compound can improve the adhesion between the steel cord and the rubber and improve the durability of the rubber composite.

The second coating film 1122 may further contain one or more elements selected from the group consisting of Sn (tin), cr (chromium), fe (iron), co (cobalt), and Ni (nickel) in addition to Cu and Zn. Accordingly, the second cover 132 may further include one or more selected from Sn, cr, fe, co and Ni, in addition to Cu and Zn. Sn, cr, fe, co, ni has a greater ionization tendency than Zn. Accordingly, the second coating 132 can function as sacrificial corrosion protection or can increase the synthetic potential of Cu and Zn by further including one or more selected from Sn, cr, fe, co and Ni in addition to Cu and Zn. Therefore, the side surface 11B of the steel cord 11 can be protected in particular, and the corrosion resistance can be further improved.

It is also more preferable for the second cover 132 to further contain S (sulfur) added at the time of vulcanization. By further containing S in the second cap 132, cu can be formed with Cu as described above ₂ S and other copper-sulfur compounds. In the case where the steel cord 11 and the rubber 12 are bonded via the second cover 132, the copper-sulfur compound can improve the adhesion between the steel cord 11 and the rubber, particularly the durability of the rubber composite.

As described above, in the rubber composite 10 of the present embodiment, the rubber 12 preferably covers at least a part of the side face 11B of the steel cord 11, and more preferably covers the entire side face 11B of the steel cord 11.

In manufacturing the rubber composite 10, by disposing the rubber 12 so as to cover at least a part of the side surface 11B of the steel cord 11 as described above, the side surface 11B of the steel cord 11 can be bonded to the rubber 12 via the second cover 132. That is, the rubber 12, the second cover 132, and the steel cord 11 are disposed in this order from the outer surface side of the rubber composite 10 on the side 11B of the steel cord 11, and the rubber 12, the second cover 132, and the steel cord 11 are bonded to each other.

As described above, the side 11B of the steel cord 11 is bonded to the rubber 12 through the second cover 132, and the side 11B of the steel cord 11 can be protected by the rubber 12 in addition to the second cover 132. Therefore, the corrosion resistance of the side surface 11B of the steel cord 11 can be improved.

In addition, when the rubber composite 10 is used for a tire or the like, a large force is easily applied near the boundary line between the side surface 11B of the steel cord 11 and the rubber 12. However, the side 11B of the steel cord 11 is bonded to the rubber 12 via the second cover 132, whereby the rubber 12, the second cover 132, and the steel cord 11 are integrated to support the applied force. Therefore, breakage of the rubber composite 10 is suppressed in particular, and durability can be improved.

In addition, by bonding the side surface 11B of the steel cord 11, the second cover 132, and the rubber 12, it is possible to prevent foreign matter such as water from entering between the members in particular. Therefore, penetration of foreign matter such as water into the side surface 11B of the steel cord 11 can be suppressed, and corrosion resistance can be improved.

However, for example, when the rubber composite 10 is used for a long period of time, the reaction between the components of the rubber 12 and the components of the second coating 1122 proceeds, and the state of the second coating 132 and the periphery thereof may change. In addition, a force may be repeatedly applied between the rubber 12 and the steel cord 11, and a gap or the like may be generated between both members. Therefore, when the rubber composite 10 is used for a long period of time, the adhesion between the rubber 12 and the steel cord 11 may be reduced.

However, even when the adhesion between the rubber 12 and the steel cord 11 is reduced, the rubber composite 10 has an effect of protecting the side surface 11B of the steel cord 11 and improving the corrosion resistance because the second cover 132 is disposed on the side surface 11B of the steel cord 11.

Therefore, the side surface 11B of the steel cord 11 is not limited to the form of adhesion to the rubber 12 via the second cover 132, and the side surface 11B of the steel cord 11 may be formed of rubber covered with the second cover.

The side surface 11B of the steel cord 11 is covered with the rubber 12 via the second cover, and the side surface 11B of the steel cord 11 can be protected by the rubber 12 in addition to the second cover 132. Therefore, the corrosion resistance of the side surface 11B of the steel cord 11 can be improved. Further, breakage of the rubber composite 10 can be suppressed, and durability of the rubber composite 10 can be improved.

The rubber covering of the side 11B of the steel cord with a second covering includes the above-mentioned adhesion and the following two forms. As the first mode, the rubber 12, the second cover 132, and the steel cord 11 are disposed in this order from the outer surface side of the rubber composite 10 on the side surface 11B of the steel cord 11, and the respective members are in contact with each other. The term "contact between the members" as used herein means a state in which the members are in contact with each other without any adhesion therebetween but without any gap. As the second form, the rubber 12, the second cover 132, and the steel cord 11 are disposed in this order from the outer surface side of the rubber composite 10 on the side surface 11B of the steel cord 11, and a gap is included in at least a part between the respective members.

In any of the modes in which the side surface 11B of the steel cord 11 is covered with rubber via the second cover 132, the second cover 1122 may be disposed on the surface of the steel cord 11 facing the second cover 132.

Tire

Next, a tire according to the present embodiment will be described with reference to fig. 4.

The tire of the present embodiment may include the rubber composite described above.

Fig. 4 is a cross-sectional view of the tire 40 according to the present embodiment, taken along a plane perpendicular to the circumferential direction. In fig. 4, only the left part of CL (center line) is shown, but the same structure is continuously provided on the right side of CL with CL as the symmetry axis.

As shown in fig. 4, the tire 40 has a tread portion 41, a sidewall portion 42, and a bead portion 43.

The tread portion 41 is a portion that contacts the road surface. The bead portion 43 is provided on the inner diameter side of the tire 40 than the tread portion 41. The bead portion 43 is a portion that contacts the rim of the wheel of the vehicle. The sidewall portion 42 connects the tread portion 41 and the bead portion 43. When the tread portion 41 receives an impact from the road surface, the sidewall portion 42 elastically deforms, absorbing the impact.

The tire 40 has an inner liner 44, a carcass 45, a belt 46, and bead wires 47.

The inner liner 44 is made of rubber, and seals the space between the tire 40 and the wheel.

Carcass 45 forms the carcass of tire 40. Carcass 45 is composed of organic fibers such as polyester, nylon, rayon, or steel cords and rubber. The carcass 45 may use the rubber composite described above.

The bead wire 47 is provided to the bead portion 43. The bead wire 47 is subjected to tensile forces acting on the carcass 45.

The belt 46 fastens the carcass 45, and increases the rigidity of the tread portion 41. In the example shown in fig. 4, the tire 40 has 2 belt layers 46.

The 2 belt layers 46 may overlap in the radial direction of the tire 40, and the rubber composite described above may be used.

The tire of the present embodiment includes the rubber composite described above. Therefore, corrosion of the end face in the longitudinal direction of the steel cord can be suppressed, and durability can be improved.

[ Steel cord ]

The steel cord of the present embodiment may have the same configuration as the steel cord 11 described in the rubber composite. Therefore, a part of the repetitive description is omitted.

Fig. 5 schematically shows a cross-sectional view of a surface of the steel cord according to the present embodiment passing through the center axis. In fig. 5, the Y-axis direction is a direction parallel to the longitudinal direction of the steel cord 11, and the XZ plane is a plane perpendicular to the longitudinal direction of the steel cord 11.

As shown in fig. 5, the steel cord 11 of the present embodiment may have a wire 111 and a coating film 112 covering the surface of the wire 111. Fig. 5 shows an example of a single-wire steel cord in which the steel cord 11 is made up of 1 wire, but is not limited to the above-described manner. For example, a steel cord formed by twisting a plurality of steel wires may be used. When the steel cord has a structure in which a plurality of steel wires are twisted, each steel wire preferably has a wire rod 111 described below and a coating film 112 covering the surface of the wire rod 111.

The wire 111 of the steel cord 11 may be, for example, a steel wire, and a high carbon steel wire is more preferably used.

The steel cord 11 may have a first coating 1121 covering an end face in the longitudinal direction of the steel cord 11 as the coating 112. The first coating 1121 may cover the entire surface of the end face 11A in the longitudinal direction of the steel cord 11, or may cover a part of the end face 11A.

In addition, the steel cord 11 may have a second coating 1122 covering the side face 11B side of the steel cord 11 as the coating 112. The second coating 1122 may cover the entire surface of the side surface 11B of the steel cord 11 or may cover a part of the side surface 11B.

By providing the coating film 112 on the surface of the wire rod 111 of the steel cord 11, the corrosion resistance of the steel cord 11 can be improved as compared with the case of the wire rod 111 alone.

When manufacturing a rubber composite using a steel cord, it is necessary to cut the steel cord to a desired size. Therefore, in the conventional steel cord, no coating film is provided on the end face in the longitudinal direction. Further, when the end face in the longitudinal direction of the steel cord is not covered with a film, corrosion occurs from the end face in the longitudinal direction of the steel cord.

In contrast, the steel cord 11 of the present embodiment has the first coating 1121 covering the end face 11A side in the longitudinal direction, and in particular, can improve corrosion resistance.

Further, the steel cord 11 of the present embodiment has the second coating 1122 covering the side surface 11B, and thus can protect the side surface 11B and improve corrosion resistance.

In order to manufacture the rubber composite 10, the first coating film 1121 may be formed after cutting the steel cord to a predetermined length. Specifically, it may be formed after cutting the steel cord 11.

The specific method for forming the first film 1121 is not particularly limited, and various methods capable of forming a film having a desired composition can be used. The first film 1121 may contain one or more kinds selected from oxides and metals, for example. Accordingly, the first film 1121 can be formed by various methods capable of forming oxides and metals. Since the method of manufacturing the first film 1121 has already been described, a description thereof will be omitted here.

The first coating 1121 provided on the end face 11A side of the steel cord 11 and the second coating 1122 provided on the side face 11B side are formed at different points. Accordingly, the first film 1121 and the second film 1122 may have the same composition and film thickness, or may have different compositions and film thicknesses.

The composition of the first film 1121 and the second film 1122 as the film 112 is not particularly limited. The first film 1121 preferably contains Cu (copper), for example. This is because the first coating 1121 contains Cu, thereby protecting the end surface of the steel cord 11 and improving corrosion resistance.

The first film 1121 more preferably further contains Zn (zinc) in addition to Cu.

Zn has a greater ionization tendency than Cu. Therefore, the second coating 1122 can function as sacrificial corrosion protection by containing Zn in addition to Cu. Therefore, the end surface 11A in the longitudinal direction of the steel cord 11 can be protected in particular, and the corrosion resistance can be further improved.

Further, the second coating film 1122 preferably further contains one or more selected from Sn (tin), cr (chromium), fe (iron), co (cobalt), and Ni (nickel) in addition to Cu and Zn.

Sn, cr, fe, co, ni has a greater ionization tendency than Zn. Therefore, the second coating film 1122 can function as sacrificial corrosion protection or can increase the synthesis potential of Cu and Zn by further including one or more selected from Sn, cr, fe, co and Ni in addition to Cu and Zn. Therefore, the end surface 11A in the longitudinal direction of the steel cord 11 can be protected in particular, and the corrosion resistance can be further improved.

The same material as that of the first film 1121 can be used for the second film 1122. That is, the second coating film 1122 preferably contains Cu. Further, the second coating film 1122 preferably further contains Zn in addition to Cu. The second coating film 1122 preferably further includes one or more selected from Sn, cr, fe, co and Ni in addition to Cu and Zn. The reason is the same as in the case of the first film 1121, and therefore, description thereof is omitted.

In the conventional steel cord, the first coating 1121 as the coating 112 is not formed on the end face 11A side of the steel cord 11. Therefore, if the first coating 1121 is disposed even in a small amount on the end face 11A of the steel cord 11, the corrosion resistance can be improved as compared with the conventional one, and the degree of disposing the first coating 1121 is not particularly limited. However, the first coating 1121 preferably covers 20% or more, more preferably 40% or more of the area of the end face 11A in the longitudinal direction of the steel cord 11. The first coating 1121 is preferable because it covers 20% or more of the area of the end face 11A in the longitudinal direction of the steel cord 11, and thus the corrosion resistance of the end face 11A of the steel cord 11 can be particularly improved.

Since the first coating 1121 may cover the entire end face 11A of the steel cord 11, the first coating 1121 may cover 100% or less of the area of the end face 11A of the steel cord 11.

The method of measuring the ratio of the area of the first coating 1121 covering the end face 11A of the steel cord 11 is not particularly limited. The evaluation can be performed as in the case of the first cover.

That is, for example, the rubber composite 10 is first produced using the steel cord 11 to be evaluated. When the end face side rubber 121 of the obtained rubber composite 10, which is a part of the rubber 12, is peeled off and disposed on the end face 11A side of the steel cord 11, the end face 11A side of the steel cord 11 is exposed as shown in fig. 3. Therefore, the ratio of the area occupied by the rubber 12 can be calculated, for example, by subtracting the exposed area of the first coating 1121 and the steel cord 11 from the end face 11A of the steel cord 11. The rubber 12 remaining on the end face 11A of the steel cord 11 corresponds to at least a portion where the first coating 1121 is formed. Therefore, as described above, the ratio of the area occupied by the rubber 12 can be calculated as the ratio of the area of the end face 11A of the steel cord 11 covered by at least the first coating 1121.

However, even at the portion where the first coating 1121 is formed, a part of the rubber may be peeled off. Therefore, the area ratio of the first coating 1121 to cover the end face 11A in the longitudinal direction of the steel cord 11 is equal to or greater than the area ratio calculated by the above method.

Further, the element distribution map of the end face 11A of the steel cord 11 may be performed, and the ratio of the area of the first coating 1121 covering the end face 11A of the steel cord 11 may be calculated.

Specifically, when the element distribution map of the end face of the steel cord 11 is performed, the region of the first coating 1121 in which the components are distributed becomes the region in which the first coating 1121 is formed. Therefore, from the result of the element distribution map, the ratio of the area of the end face 11A of the steel cord 11 covered with the first coating 1121 can be calculated by determining the ratio of the area of the end face 11A of the steel cord 11 where the first coating 1121 is formed.

The method for mapping the element distribution is not particularly limited, and SEM-EDX or the like may be used.

The thickness of the first coating film 1121 is not particularly limited, and the average thickness is preferably 5nm or more and 2 μm or less, more preferably 0.1 μm or more and 1.5 μm or less.

This is because the corrosion resistance of the end face can be particularly improved by setting the average thickness of the first coating 1121 to 5nm or more. In addition, this is because, when the rubber composite is produced, the first cover 131 having a sufficient thickness can be formed, and the corrosion resistance of the end face can be improved.

By setting the average thickness of the first coating 1121 to 2 μm or less, productivity in manufacturing the steel cord can be improved. In addition, this is because, when applied to a rubber composite, when the first coating 1121 is made too thick, the first coating 131 becomes porous, and there is a possibility that the effect of improving the corrosion resistance of the end face 11A is suppressed.

The method for obtaining the average thickness of the first coating 1121 is not particularly limited, and measurement can be performed using a fluorescent X-ray film thickness meter, for example. The measurement is performed at 3 points in total of the center of the end face 11A of the steel cord 11 and 2 measurement points on a line segment passing through the center, and the average value thereof can be used as the average thickness of the first coating 1121.

The line segment passing through the center of the end face 11A of the steel cord 11 is a line segment that becomes the diameter of a circle that is the contour line of the end face 11A. Here, the diameter of the circle, which is the contour line of the end face 11A, is set to D. In this case, the two measurement points are two points located at 0.25D from the center on a line segment which is a circle diameter that is an outline of the end face 11A and is arbitrarily drawn on the end face 11A so as to pass through the first coating 1121.

The embodiments have been described in detail above, but the present invention is not limited to the specific embodiments, and various modifications and changes can be made within the scope described in the claims.

Examples (example)

Hereinafter, specific examples will be described, but the present invention is not limited to these examples.

(evaluation method)

First, a method for evaluating a rubber composite produced in the following experimental example will be described.

(1) Evaluation of Corrosion resistance of rubber composite

In the rubber composite 10 produced in each of the following experimental examples, when the end face side rubber 121 on the end face 11A side of the steel cord 11 was peeled off, the corrosion resistance was evaluated at a ratio of the area occupied by the rubber 12 in the end face 11A in the longitudinal direction of the steel cord 11.

In the evaluation, a boundary line was visually drawn between the portion where the rubber 12 remained and the first coating 1121 and the portion where the end face 11A in the longitudinal direction of the steel cord 11 was exposed in the image of the end face 11A in the longitudinal direction of the steel cord 11 after the end face side rubber 121 was peeled off. The end face 11A is also outlined. The boundary line and the contour line of the end face 11A are lines surrounding the portion where the rubber 12 remains. Then, the portion where the rubber 12 remains surrounded by the boundary line and the contour line of the end face 11A is distinguished from the other portions by binarization processing, and the area of the portion where the rubber 12 remains is calculated.

Then, the ratio of the area occupied by the rubber 12 on one end surface in the longitudinal direction of any one of the steel cords in the rubber composite was obtained.

In the end face in the longitudinal direction of the steel cord, the area ratio of the rubber 12 is 80% or more, the ratio is a, the ratio is 60% or more and less than 80%, the ratio is B, the ratio is 20% or more and less than 60%, the ratio is C, and the ratio is less than 20%.

In each of the following experimental examples 1-1 to 1-10, 2 rubber composites were produced for evaluation. Then, the corrosion resistance was evaluated immediately after the production of one rubber composite (initial evaluation). The other rubber composite was subjected to the wet heat test and then to the evaluation of the corrosion resistance. The wet heat test is a test (wet heat evaluation) in which the rubber composite is left for 150 hours in an environment where the temperature is 80 ℃ and the relative humidity is 95%.

In both the initial evaluation and the wet heat evaluation, a is preferably evaluated to be inferior in the order of B, C, D.

When the rubber is peeled off, the rubber remaining on the end face of the steel cord corresponds to the portion where the covering is formed. Therefore, it can be said that the higher the wet heat evaluation is, the more the end face of the steel cord is protected by the stable covering after the wet heat test, and the rubber composite in which the corrosion of the end face of the steel cord is suppressed.

However, as shown in table 1, the wet heat evaluation was correlated with the initial evaluation, and when the initial evaluation was excellent, it could be said that the end face corrosion of the steel cord was suppressed. Therefore, experimental example 2 was followed by only initial evaluation.

In the initial evaluation, the rubber portion remaining on the end surface of the steel cord also corresponds to at least the portion where the first coating 1121 was formed at the time of rubber peeling. Therefore, the initial evaluation may be performed by a ratio of the area of at least the portion where the first coating 1121 is formed on the end surface of the steel cord in the longitudinal direction.

(2) Evaluation of Corrosion resistance of Steel cords

The evaluation was carried out using electrochemical measurements (LSV: linear sweep voltammetry). Specifically, the evaluation sample was immersed in an aqueous sulfuric acid solution having a pH of 1, and a current flowing at 0V (reference electrode: ag/AgCl, counter electrode: pt) was observed.

For the evaluation sample, 30 steel cords produced under the same conditions were bundled up to easily confirm the influence of the end portion, and 10mm from the end surface on which the first coating film was formed was immersed in the sulfuric acid aqueous solution, and the electric current was measured.

In the above measurement method, the current value measured for the steel cord before the plating film is formed on the end surface prepared in "(preparation of steel cord)" of Experimental example 1-1 below, that is, the corrosion current was 10mA/cm ² 。

Thus, when the measured current value is less than 10mA/cm ² In the case of (C), it was shown that the corrosion resistance was excellent, and the current value was 10mA/cm ² In the above cases, the corrosion resistance was poor.

(Experimental example)

The experimental conditions are described below.

Experimental example 1

The rubber composite and the steel cord were produced in the following steps, and the corrosion resistance was evaluated. Examples 1-1 to 1-9 are examples, and examples 1-10 are comparative examples.

Experimental example 1-1

(preparation of Steel cord)

Copper and zinc layers are formed on the surfaces of the steel filaments by plating. Copper pyrophosphate was used as the plating solution for the copper layer, and the current density was set at 22A/dm ² The film was formed with the treatment time set to 14 seconds. In addition, zinc sulfate was used as a plating solution for the zinc layer, and the current density was set to 20A/dm ² Film formation was performed with the treatment time set to 7 seconds.

Then, the metal component was diffused by heat treatment under an atmosphere at 600 ℃ for 9 seconds, thereby forming a plating film.

The obtained coated filament was subjected to drawing so that the cord diameter became 1mm.

Next, the steel cord subjected to the drawing process is cut at a plurality of positions in the longitudinal direction so as to match the size of the manufactured rubber composite. The resulting steel cord has a second coating 1122 covering the side 11B side from the coating film of the filaments. As a result of analysis of the second coating film 1122 by SEM-EDX, it was confirmed that Cu and Zn were contained.

Part of the obtained steel cord was used for the production of the following rubber composite, and the remaining part was used for the production of the steel cord described later.

(preparation of rubber composition)

A rubber composition containing a rubber component and an additive is prepared. The rubber composition contains 100 parts by mass of natural rubber as a rubber component. Further, the rubber composition contained 60 parts by mass of carbon black, 6 parts by mass of sulfur, 1 part by mass of a vulcanization accelerator, 10 parts by mass of zinc oxide, and 1 part by mass of cobalt stearate as the cobalt organic acid as additives with respect to 100 parts by mass of the rubber component.

(production of rubber composite)

The steel cord and the rubber composition were used to manufacture the rubber composite 10 shown in fig. 1 and 2.

The steel cords 11 are arranged in parallel with each other in the longitudinal direction, and the side surfaces 11B of the steel cords 11 are covered with the rubber composition, so that a precursor of the rubber composite is produced. At this time, the end face 11A in the longitudinal direction of the steel cord 11 is not covered with the rubber composition but is exposed in advance.

A resin mask having a thickness of 15 μm is disposed on the end face 11A side in the longitudinal direction of the steel cord 11 of the precursor of the rubber composite to protect the rubber composition. The resin mask has an opening at a position corresponding to the end face 11A in the longitudinal direction of the steel cord 11, and the end face 11A is exposed without being covered with the resin mask.

Next, the exposed end face 11A in the longitudinal direction of the steel cord 11 is pretreated.

The pretreatment was performed by sequentially performing electrolytic degreasing with 20 mass% sulfuric acid, water washing, electrolytic degreasing with 10 mass% sodium hydroxide aqueous solution, water washing, immersing in 1 mass% sulfuric acid, and water washing. Electrolytic degreasing with 20% by mass sulfuric acid was carried out at a liquid temperature of 45℃and a current density of 10A/dm was set ² To proceed for 1 second. Electrolytic degreasing with 10% by mass sodium hydroxide was carried out at a liquid temperature of 40℃and a current density of 10A/dm was set ² To proceed for 1 second. The immersion in 1 mass% sulfuric acid was carried out at a liquid temperature of 35℃for 1 second.

Then, a first coating 1121 is formed on the end face 11A of the steel cord 11 in the longitudinal direction by a coating method. Specifically, a conductive copper nanoink (model GO-01) manufactured by litho chemical corporation was applied to the entire end surface 11A in the longitudinal direction of the steel cord 11 and dried, thereby forming a first coating 1121 having a thickness of 0.15 μm.

The first coating 1121 is formed on the end surfaces 11A on both sides in the longitudinal direction of all the steel cords 11 contained in the rubber composite under the same conditions. Further, the average thickness of the first coating 1121 formed on the end face 11A in the longitudinal direction of the steel cord 11 was measured, and as a result, it was confirmed to be 0.15 μm.

The average thickness of the first coating 1121 was measured using a fluorescent X-ray film thickness meter. The thickness was measured at 3 points in total from the center of the end face 11A of the steel cord 11 and 2 measurement points on a line segment passing through the center, and the average value was taken as the average thickness of the first coating 1121.

The line segment passing through the center of the end face 11A of the steel cord 11 is a line segment that becomes the diameter of a circle that is the contour line of the end face 11A. When D is the diameter of the circle that is the contour line of the end face 11A, the 2 measurement points are 2 points located at 0.25D from the center on a line segment that is arbitrarily drawn on the end face 11A so as to pass through the first coating 1121 and becomes the diameter of the circle that is the contour line of the end face 11A. The average thickness of the first coating 1121 was measured in the same manner as in the other experimental examples below.

The conductive copper nanoink was coated and dried, and then the resin mask protecting the rubber composition was peeled off. Then, the rubber composition is also disposed on the end face 11A side in the longitudinal direction of the steel cord 11 of the precursor of the rubber composite.

Then, vulcanization was performed at 180℃for 10 minutes to obtain a rubber composite 10. The resulting rubber composite 10 is provided with rubber 12 so as to cover the entire surface of the steel cord 11. A first covering 131 including Cu and S is disposed on the end face 11A in the longitudinal direction of the steel cord 11. A second covering 132 containing Cu, zn, and S is disposed on the side 11B of the steel cord 11. The end face 11A and the side face 11B of the steel cord 11 are bonded to the rubber 12 via the first cover 131 and the second cover 132, respectively.

The cases where the first cap 131 contains Cu, S and the second cap 132 contains Cu, zn, S were confirmed by SEM-EDX analysis. The analysis was performed in the same manner as in examples 1-2 to 1-10 below to determine the components contained therein. In the following other experimental examples, the second cover 132 contains Cu, zn, and S, and therefore, the description thereof is omitted. In the following examples 1-2 to 1-9, 2 and 3, the first and second caps 131 and 132 each contain at least Cu and S, and it can be said that they contain a copper-sulfur compound.

The corrosion resistance of the rubber composite was evaluated using the obtained rubber composite 10. The evaluation results are shown in table 1.

As shown in the evaluation results, when the end surface side rubber 121 was peeled off in order to evaluate the corrosion resistance of the end surface 11A side in the longitudinal direction of the steel cord 11, it was confirmed that the rubber 12 remained. Therefore, as described above, the end face 11A of the steel cord 11 is bonded to the rubber 12 through the first cover 131. Similarly, when rubber is peeled off also from the side surface 11B of the steel cord 11, it can be confirmed that rubber 12 remains on the side surface 11B of the steel cord 11. Therefore, it can be said that the side surface 11B of the steel cord 11 is bonded to the rubber 12 via the second cover 132.

For the same reason, it was confirmed that the end face 11A and the side face 11B of the steel cord 11 were bonded to the rubber 12 via the first cover 131 and the second cover 132, respectively, in the following experimental examples 1-2 to 1-9.

(production of Steel cord)

The first coating 1121 was formed on the longitudinal end face 11A of the steel cord obtained in the preparation of the steel cord of the experimental example 1-1, similarly to the case of manufacturing the rubber composite in the experimental example. The first film 1121 was analyzed by SEM-EDX, and as a result, it was confirmed that Cu was contained. The average thickness of the first film 1121 was 0.15 μm.

The corrosion resistance of the steel cord was evaluated, and as a result, the current was less than 10mA/cm ² 。

Experimental examples 1-2

(production of rubber composite)

A rubber composite 10 was produced and evaluated in the same manner as in experimental example 1-1, except that the first coating 1121 was formed on the entire end face 11A of the steel cord 11 in the longitudinal direction by the plating method under the following conditions.

In this experimental example, the first coating 1121 was a laminated film in which a Cu layer and a Sn layer were laminated in this order on the end face 11A, and the first coating 1121 was formed so that the total film thickness of the Cu layer and the Sn layer became 0.15 μm. The average thickness of the first coating 1121 formed on the end face 11A in the longitudinal direction of the steel cord 11 was measured, and as a result, it was confirmed to be 0.15 μm.

The Cu layer is formed using a Cu plating solution as a pyrophosphoric acid bath. The Sn layer is formed using a Sn plating solution as a sulfuric acid bath. When each layer is formed, the sponge-carrying electrode impregnated with the plating solution is brought into contact with the end face 11A in the longitudinal direction of the steel cord 11 on which the first coating 1121 is to be formed, and power is supplied from the end face on the opposite side to the end face 11A in the longitudinal direction of the steel cord 11 on which the first coating 1121 is to be formed. The thickness of the first coating 1121 is adjusted by the supplied electric quantity.

After the first film 1121 is formed, water washing and drying are performed, and then the resin mask protecting the rubber composition is peeled off. Then, the rubber composition was also placed on the end face 11A side in the longitudinal direction of the steel cord 11 of the precursor of the rubber composite, and vulcanization was performed under the same conditions as in the case of experimental example 1-1, to obtain a rubber composite 10.

The resulting rubber composite 10 is provided with rubber 12 so as to cover the entire surface of the steel cord 11. A first covering 131 including Cu, sn, and S is disposed on the end face 11A in the longitudinal direction of the steel cord 11. A second cover 132 is disposed on the side surface 11B of the steel cord 11. The end face 11A and the side face 11B of the steel cord 11 are bonded to the rubber 12 via the first cover 131 and the second cover 132, respectively. The evaluation results are shown in table 1.

(production of Steel cord)

The first coating 1121 was formed on the longitudinal end face 11A of the steel cord obtained in the preparation of the steel cord of the experimental example 1-1, similarly to the case of manufacturing the rubber composite in the experimental example. As a result of analysis of the first coating 1121 by SEM-EDX, it was confirmed that Cu and Sn were contained. The average thickness of the first film 1121 was 0.15 μm.

Experimental examples 1-3

(production of rubber composite)

In this experimental example, the first coating 1121 is a laminated film in which a Cu layer, a Zn layer, and a Cu layer are laminated in this order on the end face 11A, and the thickness of the Cu layer is as follows: thickness of Zn layer: thickness of Cu layer = 3:4:3 and the total thickness is 0.15 μm. The average thickness of the first coating 1121 formed on the end face 11A in the longitudinal direction of the steel cord 11 was measured, and as a result, it was confirmed to be 0.15 μm.

The Cu layer is formed using a Cu plating solution as a pyrophosphoric acid bath. The Zn layer was formed using a Zn plating solution as a fluoroboric acid bath. When each layer is formed, the sponge-carrying electrode impregnated with the plating solution is brought into contact with the end face 11A in the longitudinal direction of the steel cord 11 on which the first coating 1121 is to be formed, and power is supplied from the end face on the opposite side to the end face 11A in the longitudinal direction of the steel cord 11 on which the first coating 1121 is to be formed. The thickness of the first coating 1121 is adjusted by the supplied electric quantity.

The resulting rubber composite 10 is provided with rubber 12 so as to cover the entire surface of the steel cord 11. A first covering 131 containing Cu, zn, and S is disposed on the end face 11A in the longitudinal direction of the steel cord 11. A second cover 132 is disposed on the side surface 11B of the steel cord 11. The end face 11A and the side face 11B of the steel cord 11 are bonded to the rubber 12 via the first cover 131 and the second cover 132, respectively. The evaluation results are shown in table 1.

(production of Steel cord)

The first coating 1121 was formed on the longitudinal end face 11A of the steel cord obtained in the preparation of the steel cord of the experimental example 1-1, similarly to the case of manufacturing the rubber composite in the experimental example. As a result of analysis of the first coating 1121 by SEM-EDX, it was confirmed that Cu and Zn were contained. The average thickness of the first film 1121 was 0.15 μm.

Experimental examples 1 to 4

(production of rubber composite)

In this experimental example, the first coating 1121 is a laminated film in which a Cu layer and a Zn layer are laminated in this order on the end face 11A, and the thickness of the Cu layer is as follows: thickness of Zn layer = 6:4, the first coating film 1121 is formed so that the total thickness becomes 0.15 μm. The average thickness of the first coating 1121 formed on the end face 11A in the longitudinal direction of the steel cord 11 was measured, and as a result, it was confirmed to be 0.15 μm.

(production of Steel cord)

Experimental examples 1 to 5

(production of rubber composite)

In this experimental example, the first coating 1121 was a Cu layer, and the first coating 1121 was formed so that the film thickness became 0.15 μm. The average thickness of the first coating 1121 formed on the end face 11A in the longitudinal direction of the steel cord 11 was measured, and as a result, it was confirmed to be 0.15 μm.

The Cu layer as the first coating 1121 is formed using a Cu plating solution as a pyrophosphoric acid bath. When forming the Cu layer, the sponge-carrying electrode impregnated with the plating solution is brought into contact with the end face 11A in the longitudinal direction of the steel cord 11 on which the first coating 1121 is to be formed, and power is supplied from the side opposite to the end face 11A in the longitudinal direction of the steel cord 11 on which the first coating 1121 is to be formed. The thickness of the first coating 1121 is adjusted by the supplied electric quantity.

The resulting rubber composite 10 is provided with rubber 12 so as to cover the entire surface of the steel cord 11. A first covering 131 including Cu and S is disposed on the end face 11A in the longitudinal direction of the steel cord 11. A second cover 132 is disposed on the side surface 11B of the steel cord 11. The end face 11A and the side face 11B of the steel cord 11 are bonded to the rubber 12 via the first cover 131 and the second cover 132, respectively. The evaluation results are shown in table 1.

(production of Steel cord)

Experimental examples 1 to 6

(production of rubber composite)

A rubber composite 10 was produced and evaluated in the same manner as in experimental example 1-1, except that the first coating 1121 was formed on the entire end face 11A of the steel cord 11 in the longitudinal direction by the displacement plating method under the following conditions.

The first coating 1121 was prepared by immersing the end face of the steel cord 11 in the longitudinal direction thereof, and adjusting the copper sulfate to 0.01 mol/dm ³ Is formed by washing with water and drying after 1 minute in the sulfuric acid bath.

After the first coating film 1121 is formed, a resin mask protecting the rubber composition is peeled off. Then, the rubber composition was also placed on the end face 11A side in the longitudinal direction of the steel cord 11 of the precursor of the rubber composite, and vulcanization was performed under the same conditions as in the case of experimental example 1-1, to obtain a rubber composite 10.

(production of Steel cord)

Experimental examples 1 to 7

(production of rubber composite)

In this experimental example, the first coating 1121 was a cu—zn alloy layer, and the first coating 1121 was formed so that the film thickness became 0.15 μm. The average thickness of the first coating 1121 formed on the end face 11A in the longitudinal direction of the steel cord 11 was measured, and as a result, it was confirmed to be 0.15 μm.

The cu—zn alloy layer as the first coating 1121 is formed using a plating solution obtained by adding zinc sulfate and L-histidine monohydrochloride monohydrate as additives to a pyrophosphoric acid bath for copper plating. The Cu-Zn alloy layer contains Cu and Zn in a molar ratio of Cu: zn=6: 4, and is formed in a manner of being identical to the method of the present invention. In forming the cu—zn alloy layer, the sponge-like electrode impregnated with the plating solution is brought into contact with the end face 11A in the longitudinal direction of the steel cord 11 on which the first coating 1121 is to be formed. Then, power is supplied from the surface on the opposite side to the end surface 11A in the longitudinal direction of the steel cord 11 on which the first coating 1121 is to be formed. The thickness of the first coating 1121 is adjusted by the supplied electric quantity.

(production of Steel cord)

Experimental examples 1 to 8

(production of rubber composite)

In this experimental example, the first coating 1121 was a cu—sn alloy layer, and the first coating 1121 was formed so that the film thickness became 0.15 μm. The average thickness of the first coating 1121 formed on the end face 11A in the longitudinal direction of the steel cord 11 was measured, and as a result, it was confirmed to be 0.15 μm.

The cu—sn alloy layer as the first coating 1121 is formed using a plating solution obtained by adding tin sulfate and L-histidine monohydrochloride monohydrate as additives to a pyrophosphoric acid bath for copper plating. The Cu-Sn alloy layer contains Cu in a molar ratio of Cu to Sn: sn=95: 5. In forming the cu—sn alloy layer, the sponge-like electrode impregnated with the plating solution is brought into contact with the end face 11A in the longitudinal direction of the steel cord 11 on which the first coating 1121 is to be formed. Then, power is supplied from the surface on the opposite side to the end surface 11A in the longitudinal direction of the steel cord 11 on which the first coating 1121 is to be formed. The thickness of the first coating 1121 is adjusted by the supplied electric quantity.

(production of Steel cord)

The first coating 1121 was formed on the longitudinal end face 11A of the steel cord obtained in the preparation of the steel cord of the experimental example 1-1, similarly to the case of manufacturing the rubber composite in the experimental example. As a result of analysis of the first film 1121 by SEM-EDX, it was confirmed that Cu and Sn were contained. The average thickness of the first film 1121 was 0.15 μm.

Experimental examples 1-9

(production of rubber composite)

The cu—sn alloy layer as the first coating 1121 is formed by immersing the end surface of the steel cord 11 in the longitudinal direction in a sulfuric acid bath containing copper and tin for 20 seconds, and then washing with water and drying. The Cu-Sn alloy layer contains Cu in a molar ratio of Cu to Sn: sn=95: 5.

(production of Steel cord)

Experimental examples 1 to 10

(production of rubber composite)

In manufacturing the steel cord, the steel cord subjected to the wire drawing process is cut at a plurality of positions in the longitudinal direction so as to conform to the size of the rubber composite to be manufactured, and used in a state where the first coating 1121 is not formed on the end surface and the wire 111 is exposed. Except for the above, a rubber composite was produced in the same manner as in experimental example 1-1.

The resulting rubber composite 10 is provided with rubber 12 so as to cover the entire surface of the steel cord 11. The second cover 132 is disposed on the side surface 11B of the steel cord 11, but the first cover is not formed on the end surface 11A in the longitudinal direction of the steel cord 11. The evaluation results are shown in table 1.

(production of Steel cord)

The steel cord obtained in the preparation of the steel cord of Experimental example 1-1 was evaluated for corrosion resistance of the steel cord, and as a result, the current was 10mA/cm ² 。

TABLE 1

	Initial evaluation	Damp heat evaluation
			Experimental example 1-1	A	A
Experimental examples 1-2	A	B
			Experimental examples 1 to 3	B	B
Experimental examples 1 to 4	C	C
			Experimental examples 1 to 5	A	B
Experimental examples 1 to 6	C	C
			Experimental examples 1 to 7	A	A
Experimental examples 1 to 8	B	B
			Experimental examples 1 to 9	A	A
Experimental examples 1 to 10	D	D

From the results shown in Table 1, in each of examples 1-1 to 1-9, the initial evaluation and the wet heat evaluation were A to C, and it was confirmed that the initial evaluation and the wet heat evaluation were substantially the same. In contrast, in each of examples 1 to 10, the initial evaluation and the wet heat evaluation were D, and no second coating was formed, and it was confirmed that the corrosion resistance was inferior to that of examples 1 to 9.

In addition, in the experimental examples 1-1 to 1-9, after the wet heat evaluation, the rubber remaining on the end face 11A was peeled off, and the state of the end face 11A was visually confirmed, and as a result, it was confirmed that the portion of the rubber remaining at the time of peeling off the end face side rubber 121 for the wet heat evaluation was not discolored. That is, it can be confirmed that the portion where the first cover 131 is formed can be protected from corrosion.

In contrast, in experimental examples 1 to 10, almost no rubber remained on the end face 11A and the first cover 131 was not formed at the time of the wet heat evaluation, and therefore it was confirmed that the entire end face 11A was discolored and corroded.

From the above results, it was confirmed that by providing a coating film on the end face in the longitudinal direction of the steel cord, a coating was formed on the end face in the longitudinal direction of the steel cord, and corrosion resistance was improved in the case of producing a rubber composite.

In addition, even in the case where the steel cord was not formed into a rubber composite, it was confirmed that the corrosion resistance was improved by providing a coating film on the end face in the longitudinal direction as shown in examples 1-1 to 1-9.

Experimental example 2

The rubber composite was produced in the following manner, and the corrosion resistance was evaluated. Examples 2-1 to 2-5 are examples.

Experimental example 2-1

When the first coating 1121 was formed on the entire end face 11A in the longitudinal direction of the steel cord 11 contained in the precursor of the rubber composite by the coating method, the conductive copper nanoink as the same coating liquid as in experimental example 1-1 was coated so that the thickness of the first coating 1121 after drying became 0.05 μm. The average thickness of the first coating 1121 formed on the end face 11A in the longitudinal direction of the steel cord 11 was measured, and as a result, it was confirmed to be 0.05 μm.

Except for the above, a rubber composite was produced in the same manner as in experimental example 1-1.

The resulting rubber composite 10 is provided with rubber 12 so as to cover the entire surface of the steel cord 11. A first covering 131 including Cu and S is disposed on the end face 11A in the longitudinal direction of the steel cord 11. A second cover 132 is disposed on the side surface 11B of the steel cord 11. The end face 11A and the side face 11B of the steel cord 11 are bonded to the rubber 12 via the first cover 131 and the second cover 132, respectively. The evaluation results are shown in table 2.

The first cover 131 contained Cu and S, which was confirmed by analysis using SEM-EDX. The analysis was performed in the same manner as in examples 2-2 to 2-5 and 3 below to determine the components contained therein.

Experimental example 2-2

When the first coating 1121 was formed on the entire end face 11A in the longitudinal direction of the steel cord 11 contained in the precursor of the rubber composite by the coating method, the conductive copper nanoink as the same coating liquid as in experimental example 1-1 was coated so that the thickness of the first coating 1121 obtained after drying became 0.1 μm. The average thickness of the first coating 1121 formed on the end face 11A in the longitudinal direction of the steel cord 11 was measured, and as a result, it was confirmed to be 0.1 μm.

Experimental examples 2-3

When the first coating 1121 was formed on the entire end face 11A in the longitudinal direction of the steel cord 11 contained in the precursor of the rubber composite by the coating method, the conductive copper nanoink as the same coating liquid as in experimental example 1-1 was coated so that the thickness of the first coating 1121 obtained after drying became 0.5 μm. The average thickness of the first coating 1121 formed on the end face 11A in the longitudinal direction of the steel cord 11 was measured, and as a result, it was confirmed to be 0.5 μm.

Experimental examples 2 to 4

When the first coating 1121 was formed on the entire end face 11A in the longitudinal direction of the steel cord 11 contained in the precursor of the rubber composite by the coating method, the conductive copper nanoink as the same coating liquid as in experimental example 1-1 was coated so that the thickness of the first coating 1121 obtained after drying became 1 μm. The average thickness of the first coating 1121 formed on the end face 11A in the longitudinal direction of the steel cord 11 was measured, and as a result, it was confirmed to be 1 μm.

Experimental examples 2 to 5

When the first coating 1121 was formed on the entire end face 11A in the longitudinal direction of the steel cord 11 contained in the precursor of the rubber composite by the coating method, the conductive copper nanoink as the same coating liquid as in experimental example 1-1 was coated so that the thickness of the first coating 1121 obtained after drying became 2 μm. The average thickness of the first coating 1121 formed on the end face 11A in the longitudinal direction of the steel cord 11 was measured, and as a result, it was confirmed to be 2 μm.

TABLE 2

	Evaluation results
		Experimental example 2-1	C
Experimental example 2-2	A
		Experimental examples 2 to 3	A
Experimental examples 2 to 4	B
		Experimental examples 2 to 5	C

From the results shown in table 2, it was confirmed that the corrosion resistance tended to be improved by increasing the thickness of the first coating film. This is considered to be because a cover having a sufficient thickness can be formed by setting the first film to a certain thickness or more.

Among them, as shown in examples 2 to 4 and examples 2 to 5, when the thickness of the first coating film was thicker than a certain thickness, it was confirmed that the corrosion resistance was liable to be lowered. This is thought to be because the reaction layer with S (sulfur) in the rubber is formed to be porous.

Experimental example 3

The rubber composite was produced in the following manner, and the corrosion resistance was evaluated. Examples 3-1 to 3-3 are examples.

Experimental example 3-1

When the first coating 1121 was formed on the longitudinal end face 11A of the steel cord 11 included in the precursor of the rubber composite by the coating method, the conductive copper nanoink was applied as the same coating liquid as in experimental example 1-1 so that the thickness of the first coating 1121 obtained after drying became 0.15 μm.

When the coating liquid is applied to the end face 11A in the longitudinal direction of the steel cord 11, a part of the end face 11A in the longitudinal direction of the steel cord 11 is masked in advance so that the area ratio of the area of the end face to which the coating liquid is applied is 20%. The average thickness of the first coating 1121 formed on the end face 11A in the longitudinal direction of the steel cord 11 was measured, and as a result, it was confirmed to be 0.15 μm.

The resulting rubber composite 10 is provided with rubber 12 so as to cover the entire surface of the steel cord 11. A first covering 131 including Cu and S is disposed on the end face 11A in the longitudinal direction of the steel cord 11. A second cover 132 is disposed on the side surface 11B of the steel cord 11. The end face 11A and the side face 11B of the steel cord 11 are bonded to the rubber 12 via the first cover 131 and the second cover 132, respectively. The evaluation results are shown in table 3.

Experimental example 3-2

When the coating liquid is applied to the end face 11A in the longitudinal direction of the steel cord 11, a part of the end face 11A in the longitudinal direction of the steel cord 11 is masked in advance so that the area ratio of the area of the end face to which the coating liquid is applied is 60%. The average thickness of the first coating 1121 formed on the end face 11A in the longitudinal direction of the steel cord 11 was measured, and as a result, it was confirmed to be 0.15 μm.

Experimental examples 3-3

When the coating liquid is applied to the end face 11A in the longitudinal direction of the steel cord 11, a part of the end face 11A in the longitudinal direction of the steel cord 11 is masked in advance so that the area ratio of the area of the end face to which the coating liquid is applied is 80%. The average thickness of the first coating 1121 formed on the end face 11A in the longitudinal direction of the steel cord 11 was measured, and as a result, it was confirmed to be 0.15 μm.

TABLE 3

	Evaluation results
		Experimental example 3-1	C
Experimental example 3-2	B
		Experimental examples 3 to 3	A

From the results shown in table 3, it was confirmed that the higher the ratio of the area of the region coated with the coating liquid in the end face in the longitudinal direction of the steel cord, the higher the result of the corrosion resistance test. In the end face of the steel cord in the longitudinal direction, the proportion of the area covered with the coating liquid increases, and the proportion of the area covered with the coating film increases in the end face of the steel cord in the longitudinal direction. As a result, it is considered that corrosion resistance can be improved.

Symbol description

10. Rubber composite

11. Steel cord

11A end face

11B side

111. Wire rod

112. Film coating

1121. First coating film

1122. Second coating film

12. Rubber material

121. End face side rubber

13. Covering material

131. First cover

132. Second cover

X X axial direction (width direction)

Y Y axial direction (longitudinal direction)

Z Z axial direction (thickness direction)

40. Tire with a tire body

41. Tread portion

42. Sidewall portion

43. Bead portion

44. Lining(s)

45. Carcass (rubber complex)

46. Belted layer (rubber complex)

47. Bead wire

Claims

1. A rubber composite, wherein the rubber composite has:

steel cord, and

a rubber covering at least a portion of a surface of the steel cord, wherein

A Cu-containing first coating is disposed on the longitudinal end face of the steel cord, and the Cu-containing first coating is derived from a Cu-containing first coating film having an average thickness of 0.1 μm to 1 μm formed on the longitudinal end face of the steel cord.

2. The rubber composite of claim 1, wherein the first cover is a reactant of a component contained in the first cover and a component contained in the rubber.

3. The rubber composite of claim 1 or claim 2, wherein the first covering further comprises Zn.

4. A rubber composite as in claim 3 wherein said first cover further comprises one or more selected from Sn, cr, fe, co and Ni.

5. The rubber composite of claim 1 or claim 2, wherein the end face of the steel cord is covered with the rubber via the first cover.

6. The rubber composite of claim 1 or claim 2, wherein the end face of the steel cord is bonded to the rubber via the first covering.

7. The rubber composite of claim 1 or claim 2, wherein the first cover covers 20% or more of the end face.

8. The rubber composite according to claim 1 or claim 2, wherein a second covering containing Cu is disposed on a side surface of the steel cord.

9. A tire, wherein the tire comprises the rubber composite of any one of claims 1 to 8.