JP2023077085A - Vulcanized rubber-metal complex and tire, hose, and crawler - Google Patents

Abstract

To provide a vulcanized rubber-metal complex that excels in crack resistance, low pyrogenicity, and adhesion between vulcanized rubber and metal, and a tire that comprises the vulcanized rubber-metal complex and excels in durability, a hose, and a crawler.SOLUTION: A vulcanized rubber-metal complex comprises a metal, and a vulcanized rubber that coats the metal. The vulcanized rubber is a vulcanized rubber of a rubber composition that comprises a rubber component, carbon black, and silica, with a content of a cobalt-containing compound being 0.01 pts.mass or less being relative to 100 pts.mass of the rubber component. In the rubber composition, the content of the cobalt-containing compound is 0.01 pts.mass or less being relative to 100 pts.mass of the rubber component. The metal is a metal having a steel cord surface being coated with ternary plating of copper, zinc, and iron.SELECTED DRAWING: None

Description

This invention relates to vulcanized rubber-metal composites and tires, hoses, and crawlers.

Steel cords made of steel wires are often used as reinforcing elements for rubber articles typified by pneumatic tires. In steel cord-rubber composites reinforced with steel cords, brass plating (Cu and Zn dual plating) is applied to the steel cord side in order to increase the adhesion between the steel cord and the rubber. Sulfur (S) contained in the rubber and copper (Cu) in the brass plating layer are cross-linked and bonded to form an adhesive layer (a layer containing Cu ₂ S or CuS) between the brass plating layer and the rubber. ) is known to develop adhesion between the brass plating layer and the rubber.
However, simply applying brass plating to the surface of the steel wire has the problem that the adhesiveness at the initial stage of vulcanization and the adhesiveness in a high-temperature, high-humidity, wet-heat environment (wet-heat adhesiveness) are insufficient.

Therefore, for the purpose of improving initial adhesiveness and wet heat adhesiveness, there is known a technique of blending an organic cobalt salt into rubber. However, the organic cobalt salt is expensive and tends to deteriorate unvulcanized rubber. In addition, when the temperature in the rubber kneading process is increased, the deterioration of the rubber is accelerated by cobalt, so there is a problem that productivity is lowered, such as the need to lower the temperature and lengthen the kneading time. Furthermore, in recent years, from the viewpoint of reducing the burden on the environment, there has been a demand for reducing the amount of cobalt used.

In order to solve such a problem, for example, Patent Document 1 discloses that a ternary plating in which the contents of copper, zinc, and cobalt are set within a predetermined range in the plating surface area is adopted, whereby an organic cobalt salt is added to the rubber. A technique is disclosed that can improve the adhesion between rubber and steel cords without blending.

Also, US Pat. No. 6,200,000 discloses a steel cord with an iron particle-rich brass coating that allows the use of ternary alloy coatings even with cobalt-free compounds.

JP 2014-231580 A WO2020/156967

However, in the steel cord/rubber composite of Patent Document 1, although the adhesiveness between the rubber and the steel cord can be improved, the crack resistance of the rubber needs to be further improved.
Furthermore, in recent years, from the viewpoint of improving the fuel economy performance of automobiles, there is an increasing demand for improvement in the low heat build-up of rubber coating steel cords in order to reduce the rolling resistance of tires. In response to such demands, a technique for manufacturing a rubber composition with reduced hysteresis loss by reducing the amount of carbon black used or using low-grade carbon black and applying it to a steel cord-rubber composite. It has been known.
However, when a rubber composition with a reduced carbon black content or a rubber composition using low-grade carbon black is used in the above-described steel cord-rubber composite, a certain improvement in loss reduction is achieved. Although obtained, sufficient crack resistance could not be obtained.
In addition, the vulcanized rubber-metal composite described in Patent Document 2 is insufficient in crack resistance and low heat build-up.

In view of the above circumstances, the present invention provides a vulcanized rubber-metal composite having excellent crack resistance, low heat build-up and adhesiveness between vulcanized rubber and metal, and tires, hoses, and crawlers having excellent durability using the same. The purpose is to provide and the problem is to solve the purpose.

<1> A vulcanized rubber-metal composite comprising a vulcanized rubber and a metal, wherein the vulcanized rubber and the metal are bonded together,
The vulcanized rubber is a vulcanized rubber of a rubber composition containing a rubber component, carbon black, and silica, and having a cobalt-containing compound content of 0.01 parts by mass or less with respect to 100 parts by mass of the rubber component. can be,
The metal is a vulcanized rubber-metal composite in which the surface of the steel cord is coated with ternary plating of copper, zinc, and iron.

<2> The vulcanized rubber-metal composite according to <1>, wherein the amount of the iron in the coating is 1% by mass or more and less than 10% by mass of the total mass of the copper, the zinc and the iron.
<3> The vulcanized rubber-metal composite according to <1> or <2>, wherein the amount of phosphorus in the coating is more than 0 mg/m ² and not more than 4 mg/m ² .
<4> The vulcanized rubber-metal composite according to any one of <1> to <3>, wherein the steel cord is drawn with a diamond die.

<5> Any one of <1> to <4>, wherein the ratio (c:s) of the carbon black content c to the silica content s is 60:40 to 85:15 on a mass basis The vulcanized rubber-metal composite according to 1.
<6> The vulcanized rubber-metal composite according to any one of <1> to <5>, wherein the carbon black has a cetyltrimethylammonium bromide adsorption specific surface area of 110 to 160 m ² /g.

<7> The carbon black has a peak half-value width ΔD50 of 60 nm or less including the Stokes equivalent diameter Dst, which indicates the highest frequency in the aggregate distribution obtained by the centrifugal sedimentation method, and the ratio of the ΔD50 to the Dst The vulcanized rubber-metal composite according to any one of <1> to <6>, wherein (ΔD50/Dst) is 0.95 or less.
<8> The vulcanized rubber-metal composite according to any one of <1> to <7>, wherein the silica has a cetyltrimethylammonium bromide adsorption specific surface area of 200 m ² /g or more.
<9> The vulcanized rubber according to any one of <1> to <8>, wherein the total content of the carbon black and the silica is 30 to 80 parts by mass with respect to 100 parts by mass of the rubber component. - Metal composites.

<10> The vulcanized rubber-metal composite according to any one of <1> to <9>, wherein the rubber composition contains a vulcanizing agent and a vulcanization accelerator.

<11> The vulcanized rubber-metal composite according to any one of <1> to <10>, wherein the carbon black has a compressed dibutyl phthalate absorption of 80 to 110 cm ³ /100 g.
<12> The vulcanized rubber-metal composite according to any one of <1> to <11>, wherein the silica content is 5 to 25 parts by mass with respect to 100 parts by mass of the rubber component.
<13> The vulcanization according to any one of <1> to <12>, wherein the content of the cobalt-containing compound in the rubber composition is 0.00 parts by mass with respect to 100 parts by mass of the rubber component. Rubber-metal composite.
<14> Any one of <5> to <13>, wherein the ratio (c:s) of the carbon black content c to the silica content s is 76:24 to 85:15 on a mass basis A vulcanized rubber-metal composite according to one.

<15> A tire comprising the vulcanized rubber-metal composite according to any one of <1> to <14>.
<16> The tire according to <15>, wherein the cobalt atom content is 1% by mass or less.
<17> A hose comprising the vulcanized rubber-metal composite according to any one of <1> to <14>.
<18> A crawler comprising the vulcanized rubber-metal composite according to any one of <1> to <14>.

According to the present invention, a vulcanized rubber-metal composite having excellent crack resistance, low heat build-up, and excellent adhesion between vulcanized rubber and metal, and tires, hoses, and crawlers having excellent durability using the same are provided. be able to.

Fig. 3a of Patent Document 2;

The present invention will be described in detail below based on its embodiments. In the following description, the description of "A to B" indicating a numerical range represents a numerical range including A and B, which are end points, and "A or more and B or less" (when A < B), or "A hereinafter B or more” (when A>B).
Parts by mass and % by mass are synonymous with parts by weight and % by weight, respectively.

<Vulcanized rubber-metal composite>
The vulcanized rubber-metal composite of the present invention is a vulcanized rubber-metal composite comprising a metal and a vulcanized rubber covering the metal.
Here, the vulcanized rubber includes a rubber component, carbon black, and silica, and the content of the cobalt-containing compound is 0.01 parts by mass or less with respect to 100 parts by mass of the rubber component. is rubber.
The vulcanized rubber is sometimes referred to as "the vulcanized rubber of the present invention".
The rubber composition from which the vulcanized rubber of the present invention is based is sometimes referred to as the "rubber composition of the present invention". The rubber composition is in an unvulcanized state, and the rubber component contained in the rubber composition is also in an unvulcanized state.
In the vulcanized rubber-metal composite of the present invention, the metal is a metal whose steel cord surface is coated with ternary plating of copper, zinc and iron (ternary plated metal).
The vulcanized rubber-metal composite in which the vulcanized rubber having the above structure covers the metal having the above structure is the vulcanized rubber-metal composite of the present invention, or the vulcanized rubber of the present invention according to the first embodiment. - referred to as metal composites.

The reason why the vulcanized rubber-metal composite of the present invention is excellent in durability and adhesiveness between vulcanized rubber and metal is not clear, but the surface of the steel cord is coated rubber with copper-zinc-iron ternary plated metal. As a result, it was found that the effect can be achieved by using the vulcanized rubber of the rubber composition of the present invention having the above configuration.

The vulcanized rubber-metal composite of the present invention is not particularly limited as long as it satisfies the requirements of the vulcanized rubber-metal composite of the present invention according to the first embodiment, for example, the following second implementation It may be a vulcanized rubber-metal composite according to the form.

The vulcanized rubber-metal composite of the present invention according to the second embodiment is
A vulcanized rubber-metal composite comprising a metal and a vulcanized rubber covering the metal,
The vulcanized rubber is a vulcanized rubber of a rubber composition containing a rubber component, carbon black, silica, a vulcanizing agent, and a vulcanization accelerator,
The carbon black has a cetyltrimethylammonium bromide adsorption specific surface area of 110 to 160 m ² /g, and a peak half-value width ΔD50 of 60 nm including the Stokes equivalent diameter Dst, which indicates the highest frequency in the aggregate distribution obtained by the centrifugal sedimentation method. and the ratio of the ΔD50 to the Dst (ΔD50/Dst) is 0.95 or less,
The silica has a cetyltrimethylammonium bromide adsorption specific surface area of 200 m ² /g or more,
The total content of the carbon black and the silica is 30 to 80 parts by mass with respect to 100 parts by mass of the rubber component, and the ratio of the content of the carbon black and the silica (carbon black content: content of silica) is 60:40 to 85:15,
A vulcanized rubber of a rubber composition in which the content of a cobalt-containing compound in the rubber composition is 0.01 parts by mass or less with respect to 100 parts by mass of the rubber component,
The metal is a metal whose steel cord surface is coated with ternary plating of copper, zinc, and iron.

Hereinafter, the cetyltrimethylammonium bromide adsorption specific surface area may be referred to as "CTAB adsorption specific surface area" or simply "CTAB".
Dibutyl phthalate absorption is sometimes referred to as "DBP absorption" or simply "DBP".
Compressed dibutyl phthalate absorption may be described as "24M4DBP absorption" or simply "24M4DBP".
The rubber composition and metal of the present invention are described below.

[Rubber composition]
The rubber composition of the present invention contains a rubber component, carbon black, and silica, and the content of the cobalt-containing compound is 0.01 parts by mass or less per 100 parts by mass of the rubber component.
The rubber composition of the present invention may further contain vulcanizing agents, vulcanization accelerators, stearic acid, zinc white and the like.

(rubber component)
The rubber component is not particularly limited. For example, at least one diene rubber selected from the group consisting of natural rubber (NR) and synthetic diene rubber can be included.
Examples of synthetic diene rubber include isoprene rubber, polybutadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), butadiene-isoprene rubber (BIR), styrene-isoprene rubber (SIR), styrene-butadiene- Examples include isoprene rubber (SBIR), isobutylene-isoprene rubber (IIR), and modified rubbers thereof. Moreover, the rubber component may contain a non-diene rubber as long as it does not impair the effects of the present invention.
Only one kind of rubber component may be used, or two or more kinds may be mixed and used.

From the viewpoint of improving the crack resistance without reducing the low heat build-up of the vulcanized rubber, the rubber component includes diene rubbers such as natural rubber, isoprene rubber, styrene-butadiene copolymer rubber, butadiene rubber, and , isobutylene-isoprene rubber, and more preferably at least one selected from the group consisting of natural rubber and butadiene rubber.
Furthermore, the rubber component preferably contains at least natural rubber from the viewpoint of improving the crack resistance without lowering the low heat build-up of the vulcanized rubber. Furthermore, when the rubber component contains natural rubber, the content of natural rubber in the rubber component is preferably 70% by mass or more from the viewpoint of further improving the wear resistance and crack resistance of the vulcanized rubber. It is preferably 80% by mass or more, more preferably 100% by mass.
The rubber component may also contain non-diene rubber as long as the effects of the present invention are not impaired.

(filler)
From the viewpoint of improving the mechanical strength of the vulcanized rubber, the rubber composition of the present invention contains carbon black and silica as fillers.
The filler is a reinforcing filler that reinforces the rubber composition, and in addition to carbon black and silica, metal oxides such as alumina, titania, and zirconia; metal carbonates such as magnesium carbonate and calcium carbonate; aluminum hydroxide, etc. may contain
Only one filler may be used, or two or more fillers may be used.

[Carbon black]
The carbon black preferably has a cetyltrimethylammonium bromide adsorption specific surface area of 110 to 160 m ² /g.
When the CTAB adsorption specific surface area of the carbon black is 110 m ² /g or more, the vulcanized rubber has sufficient wear resistance, and when it is 160 m ² /g or less, the vulcanized rubber has lower heat build-up. Excellent for
From the viewpoint of further improving the crack resistance of vulcanized rubber, the CTAB adsorption specific surface area of carbon black is more preferably 115 m ² /g or more, and still more preferably 120 m ² /g or more. Further, from the viewpoint of further improving the low heat build-up of vulcanized rubber, the CTAB adsorption specific surface area of carbon black is more preferably 157 m ² /g or less, and even more preferably 153 m ² /g or less.
The CTAB adsorption specific surface area of carbon black can be measured by a method conforming to JIS K 6217-3: 2001 (Determination of specific surface area - CTAB adsorption method).

From the viewpoint of further improving the crack resistance of the vulcanized rubber, the carbon black has a peak half width ΔD50 of 60 nm or less, Moreover, the ratio of ΔD50 to Dst (ΔD50/Dst) is preferably 0.95 or less.

The crack resistance of the vulcanized rubber can be improved by setting the half width ΔD50 of the peak containing the Stokes equivalent diameter Dst, which shows the highest frequency in the aggregate distribution obtained by the centrifugal sedimentation method, to 60 nm or less. Although the lower limit of ΔD50 is not particularly limited, it is preferably 20 nm or more from the viewpoint of manufacturability of the vulcanized rubber-metal composite.
Furthermore, from the viewpoint of achieving both crack resistance and manufacturability of the vulcanized rubber, the ΔD50 of carbon black is more preferably 20 to 55 nm, and even more preferably 25 to 50 nm.
The half-value width ΔD50 (nm) is the width of the distribution at half the height of the maximum frequency point in the aggregate distribution curve obtained by the centrifugal sedimentation method. The Stokes equivalent diameter Dst is an aggregate size giving the highest frequency of aggregate distribution obtained by centrifugal sedimentation according to the method described in JIS K6217-6, and is also called Stokes sedimentation diameter. This Dst is defined as the average diameter of carbon black aggregates. Further, in the present invention, the aggregate distribution of carbon black means the aggregate distribution on a volume basis.

Furthermore, by setting the ratio of ΔD50 to Dst (ΔD50/Dst) to 0.95 or less, the vulcanized rubber can achieve excellent crack resistance. Although the lower limit of the ratio of ΔD50 to Dst (ΔD50/Dst) is not particularly limited, it is preferably 0.50 or more from the viewpoint of further improving the low heat build-up of the vulcanized rubber. Further, from the viewpoint of achieving a higher level of both crack resistance and low heat build-up of the vulcanized rubber, ΔD50/Dst is more preferably 0.50 to 0.90, more preferably 0.55 to 0. 0.87 is even more preferred.

Carbon black preferably has a compressed dibutyl phthalate absorption (24M4DBP absorption) of 80 to 110 cm ³ /100 g.
By setting the 24M4DBP absorption amount of carbon black to 80 cm ³ /100 g or more, the rubber-capturing power can be enhanced, and the wear resistance and crack resistance of the vulcanized rubber can be improved ^. In addition, the exothermicity of the vulcanized rubber is lowered, and the viscosity of the rubber composition is lowered, thereby improving the processability of the rubber composition in the factory. Furthermore, from the same point of view, the 24M4DBP absorption of carbon black is more preferably 80 to 105 cm ³ /100 g, more preferably 80 to 100 cm ³ /100 g.

The 24M4DBP absorption amount (cm ³ /100 g) of carbon black is a value obtained by measuring the dibutyl phthalate absorption amount (DBP absorption amount) after repeatedly applying pressure at a pressure of 24,000 psi four times in accordance with ISO 6894. is. This 24M4 DBP absorption eliminates the DBP absorption due to the deformable and destructive structural form (secondary structure) caused by the so-called van der Waals force, and the structural form of the nondestructive true structure (primary structure). It is an index for evaluating the skeletal structure specification of carbon black mainly composed of the primary structure, which is used when determining the DBP absorption amount based on .

The type of carbon black is not particularly limited, and examples thereof include carbon blacks such as GPF, FEF, HAF, ISAF, and SAF, and commercially available products may be used. Only one type of carbon black may be used, or two or more types may be used.

In carbon black, the total content d of the content c (mass) of carbon black and the content s (mass) of silica described later is 30 to 80 parts by mass with respect to 100 parts by mass of the rubber component. preferable.
When the total content d of carbon black and silica is 30 parts by mass or more with respect to 100 parts by mass of the rubber component, the crack resistance of the vulcanized rubber is further improved, and when it is 80 parts by mass or less, The low heat build-up of the vulcanized rubber can be further improved. From the viewpoint of improving the crack resistance of the vulcanized rubber, the total content of carbon black and silica is more preferably 40 parts by mass or more, more preferably 45 parts by mass or more with respect to 100 parts by mass of the rubber component. More preferred. In addition, from the viewpoint of improving the low heat build-up of the vulcanized rubber, the total content d is more preferably 70 parts by mass or less, more preferably 60 parts by mass or less per 100 parts by mass of the rubber component. preferable.
In addition, about content of carbon black and silica, when using multiple types of carbon black and silica, let content be the total amount of multiple types. For example, when two types of carbon black 1 with a content c1 and carbon black 2 with a content c2 are included, the content c of carbon black is calculated as c1+c2.

Furthermore, the ratio (c:s) of the carbon black content c to the silica content s in the rubber composition is preferably 60:40 to 85:15 on a mass basis.
This ratio means that the carbon black content ratio [(c/d) × 100] with respect to the total content d of the carbon black content c and the silica content s is 60 to 85% by mass. . When the content of carbon black with respect to the total content d is 60% by mass or more, the crack resistance of the vulcanized rubber can be further improved, and when it is 85% by mass or less, the content of the vulcanized rubber Low heat build-up can be further improved.
From the same point of view, the content of carbon black in the total content d is more preferably 65 to 85% by mass (the content of silica is 35 to 15% by mass), and 70 to 85% by mass. (The content of silica is 30 to 15% by mass), more preferably 76 to 85% by mass (The content of silica is 24 to 15% by mass).

[silica]
Silica preferably has a cetyltrimethylammonium bromide adsorption specific surface area (CTAB adsorption specific surface area) of 200 m ² /g or more.
By setting the CTAB adsorption specific surface area of silica to 200 m ² /g or more, the crack resistance of the vulcanized rubber can be further enhanced.
The CTAB adsorption specific surface area of silica can be measured by a method conforming to the method of ASTM-D3765-80.

The CTAB adsorption specific surface area of silica is preferably 210 m 2 /g or more, more preferably 220 ^{m 2 /} g or more, more preferably 230 m ² /g, from the viewpoint of obtaining a vulcanized rubber having superior crack resistance. g or more is more preferable.
Although the upper limit of the CTAB adsorption specific surface area of silica is not particularly limited, silica exceeding 300 m ² /g cannot be obtained at present.

Silica preferably has a specific surface area (BET specific surface area) of 100 to 300 m ² /g, more preferably 150 to 250 m ² /g, as measured by the BET method. By setting the BET specific surface area of silica to 100 to 300 m ² /g, it is possible to suppress the aggregation of silica and secure the surface area required for rubber reinforcement, resulting in low heat build-up and crack resistance of vulcanized rubber. and can be achieved at a higher level.
The BET specific surface area of silica can be measured according to the method of JISK 6430:2008.

The type of silica is not particularly limited, and examples thereof include wet silica, colloidal silica, calcium silicate, and aluminum silicate.
Among them, silica is preferably wet silica, and more preferably precipitated silica. These silicas have high dispersibility in the rubber composition, can improve the low heat build-up of the vulcanized rubber, and further improve the crack resistance.
In addition, precipitated silica means that in the early stage of production, the reaction solution is reacted at a relatively high temperature and in a neutral to alkaline pH range to grow primary silica particles, and then controlled to the acidic side to aggregate the primary particles. It is the silica obtained as a result of
Silica may be a commercial product, for example, available as Zeosil Premium 200MP (trade name) from Rhodia.
Only one type of silica may be used, or two or more types may be used.

The content of silica in the rubber composition is preferably 2 to 25 parts by mass, more preferably 5 to 25 parts by mass, and 5 to 14 parts by mass with respect to 100 parts by mass of the rubber component. is more preferable. If the content of silica is 2 parts by mass or more with respect to 100 parts by mass of the rubber component, the crack resistance of the vulcanized rubber can be further improved. Hard to lose.

[Silane coupling agent]
Since the rubber composition contains silica, a silane coupling agent is added to improve the dispersibility of silica in the rubber composition after strengthening the bond between the silica and the rubber component to further enhance the reinforcing property. can also include
The content of the silane coupling agent in the rubber composition is preferably 5 to 15 parts by mass or less with respect to 100 parts by mass of silica. When the content of the silane coupling agent is 15 parts by mass or less with respect to 100 parts by mass of silica, the effect of improving the dispersibility of silica in the rubber composition is obtained, and economic efficiency is less likely to be impaired. Further, when the content of the silane coupling agent is 5 parts by mass or more with respect to 100 parts by mass of silica, the dispersibility of silica in the rubber composition can be enhanced.

A silane coupling agent is not particularly limited. For example, bis(3-triethoxysilylpropyl) disulfide, bis(3-triethoxysilylpropyl) trisulfide, bis(3-triethoxysilylpropyl) tetrasulfide, bis(3-trimethoxysilylpropyl) disulfide, bis( 3-trimethoxysilylpropyl) trisulfide, bis(3-trimethoxysilylpropyl) tetrasulfide, bis(2-triethoxysilylethyl) disulfide, bis(2-triethoxysilylethyl) trisulfide, bis(2-tri ethoxysilylethyl) tetrasulfide, 3-trimethoxysilylpropyl benzothiazole disulfide, 3-trimethoxysilylpropyl benzothiazole trisulfide, 3-trimethoxysilylpropyl benzothiazole tetrasulfide and the like.

(vulcanizing agent)
Preferably, the rubber composition further contains a vulcanizing agent.
Although the content of the vulcanizing agent in the rubber composition is not particularly limited, it is preferably 3.0 to 7.0 parts by mass with respect to 100 parts by mass of the rubber component. This is because by containing the vulcanizing agent in the above range, the strength (crack resistance, etc.) of the vulcanized rubber can be increased without lowering the adhesion between the vulcanized rubber and metal.
The type of vulcanizing agent is not particularly limited, and examples thereof include sulfur.

(Vulcanization accelerator)
The rubber composition preferably further contains a vulcanization accelerator.
By including a vulcanization accelerator in the rubber composition, the vulcanization of the rubber composition can be accelerated and the strength of the vulcanized rubber can be further increased.
The type of vulcanization accelerator is not particularly limited, and vulcanization accelerators such as guanidine-based, aldehyde-amine-based, aldehyde-ammonia-based, thiazole-based, sulfenamide-based, thiourea-based, dithiocarbamate-based, xanthate-based, etc. agents. These vulcanization accelerators may be used alone or in combination of two or more.

Among them, it is preferable to use a sulfenamide-based vulcanization accelerator from the viewpoint of further increasing the strength of the vulcanized rubber.
Sulfenamide-based vulcanization accelerators include, for example, N-cyclohexyl-2-benzothiazolylsulfenamide, N,N-dicyclohexyl-2-benzothiazolylsulfenamide, N-tert-butyl-2- Benzothiazolylsulfenamide, N-oxydiethylene-2-benzothiazolylsulfenamide, N-methyl-2-benzothiazolylsulfenamide, N-ethyl-2-benzothiazolylsulfenamide, N-propyl -2-benzothiazolylsulfenamide, N-butyl-2-benzothiazolylsulfenamide, N-pentyl-2-benzothiazolylsulfenamide, N-hexyl-2-benzothiazolylsulfenamide, N -heptyl-2-benzothiazolylsulfenamide, N-octyl-2-benzothiazolylsulfenamide, N-2-ethylhexyl-2-benzothiazolylsulfenamide, N-decyl-2-benzothiazolylsulfenamide phenamide, N-dodecyl-2-benzothiazolylsulfenamide, N-stearyl-2-benzothiazolylsulfenamide, N,N-dimethyl-2-benzothiazolylsulfenamide, N,N-diethyl- 2-benzothiazolylsulfenamide, N,N-dipropyl-2-benzothiazolylsulfenamide, N,N-dibutyl-2-benzothiazolylsulfenamide, N,N-dipentyl-2-benzothiazol Rusulfenamide, N,N-dihexyl-2-benzothiazolylsulfenamide, N,N-diheptyl-2-benzothiazolylsulfenamide, N,N-dioctyl-2-benzothiazolylsulfenamide, N , N-di-2-ethylhexylbenzothiazolylsulfenamide, N,N-didecyl-2-benzothiazolylsulfenamide, N,N-didodecyl-2-benzothiazolylsulfenamide, N,N-di and stearyl-2-benzothiazolylsulfenamide.
Among these, the vulcanization accelerator more preferably contains at least N-cyclohexyl-2-benzothiazolylsulfenamide.

The content of the vulcanization accelerator in the rubber composition is preferably 0.8 parts by mass or more with respect to 100 parts by mass of the rubber component from the viewpoint of further improving the low heat build-up and crack resistance of the vulcanized rubber. , more preferably 0.9 parts by mass or more, preferably 3 parts by mass or less, more preferably 2.5 parts by mass or less, and even more preferably 2.3 parts by mass or less.

(Various components)
The rubber composition can contain other components to the extent that they do not impair the effects of the invention.
Other components include additives commonly used in the rubber industry, such as softeners, stearic acid, anti-aging agents, zinc oxide, resins, waxes and oils, as long as they do not impair the object of the present invention. can be included as appropriate within

[Anti-aging agent]
Among the other components, the anti-aging agent is not particularly limited, and examples thereof include anti-aging agents such as amine-based, quinoline-based, quinone-based, phenol-based, and imidazole-based compounds, and metal carbamates.

Examples of the amine anti-aging agent include phenylenediamine anti-aging agents having a phenylenediamine skeleton (--NH--Ph--NH--).
Specifically, for example, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, N,N'-diphenyl-p- Phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, N-cyclohexyl-N'-phenyl-p-phenylenediamine, N,N'-bis(1-methylheptyl)-p-phenylenediamine , N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine , N,N'-dicyclohexyl-p-phenylenediamine , N,N'-bis(1-ethyl-3-methylpentyl)- p-phenylenediamine, N-4-methyl-2-pentyl-N'-phenyl-p-phenylenediamine, N,N'-diaryl-p-phenylenediamine, hindered diaryl-p-phenylenediamine, phenylhexyl-p -phenylenediamine, phenyloctyl-p-phenylenediamine, and the like.

Among them, it is preferable to have no double bond other than the phenylenediamine moiety (-NH-Ph-NH-). Specifically, the following formula (1) (R ¹ -NH-Ph-NH-R ² ) An amine anti-aging agent represented by is preferred.

In formula (1) above, R ¹ and R ² are each independently a monovalent saturated hydrocarbon group.
R ¹ and R ² may be the same or different, but are preferably the same from the viewpoint of synthesis.

The monovalent saturated hydrocarbon group preferably has 1 to 20 carbon atoms, more preferably 3 to 10 carbon atoms, and particularly preferably 6 and 7 carbon atoms. When the number of carbon atoms in the saturated hydrocarbon group is 20 or less, the number of moles per unit mass increases, so that the anti-aging effect increases and the ozone resistance of the vulcanized rubber of the rubber composition improves.
From the viewpoint of further improving the ozone resistance of the vulcanized rubber of the rubber composition, R ¹ and R ² in the above formula (1) each independently represent a linear or cyclic monovalent monovalent compound having 1 to 20 carbon atoms. A saturated hydrocarbon group is preferred.

Examples of the monovalent saturated hydrocarbon group include an alkyl group and a cycloalkyl group. The alkyl group may be linear or branched, and the cycloalkyl group may further include an alkyl group as a substituent. etc. may be combined.
Examples of the alkyl group include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, 1,2-dimethylbutyl group, 1,3- dimethylbutyl group, 2,3-dimethylbutyl group, n-pentyl group, isopentyl group, neopentyl group, 1-methylpentyl group, 2-methylpentyl group, 3-methylpentyl group, 4-methylpentyl group, 1,2 -dimethylpentyl group, 1,3-dimethylpentyl group, 1,4-dimethylpentyl group, 2,3-dimethylpentyl group, 2,4-dimethylpentyl group, 3,4-dimethylpentyl group, n-hexyl group, Examples include 1-methylhexyl group, 2-methylhexyl group, various octyl groups, various decyl groups, various dodecyl groups, etc. Among these, 1,4-dimethylpentyl group is preferred.
Examples of the cycloalkyl group include a cyclopentyl group, a methylcyclopentyl group, a cyclohexyl group, a methylcyclohexyl group, a cycloheptyl group, a cyclooctyl group, etc. Among these, a cyclohexyl group is preferred.

The amine anti-aging agent represented by formula (1) may be carried on any carrier. For example, the amine anti-aging agent represented by formula (1) may be carried on inorganic fillers such as silica and calcium carbonate.
Moreover, the amine anti-aging agent represented by Formula (1) may constitute a masterbatch together with the rubber component. Here, the rubber component used in forming the masterbatch is not particularly limited, and may be diene rubber such as natural rubber (NR), ethylene-propylene-diene rubber (EPDM), or the like. .
Moreover, the amine anti-aging agent represented by Formula (1) may be a salt with an organic acid. Here, the organic acid used for forming the salt is not particularly limited, but stearic acid and the like can be mentioned.

A quinoline anti-aging agent can also be suitably used. 4-trimethyl-1,2-dihydroquinoline and the like.
The above anti-aging agents may be used alone or in combination of two or more.
Among the above, the anti-aging agent preferably contains one or more selected from the group consisting of an amine-based anti-aging agent and a quinoline-based anti-aging agent, and more preferably includes at least an amine-based anti-aging agent.

[Zinc white]
Among other components, zinc white (ZnO) is used as a vulcanization accelerator aid.
By further including zinc white in the rubber composition, the vulcanization of the rubber composition can be accelerated and the strength of the vulcanized rubber can be further increased.
Here, the content of zinc white in the rubber composition is not particularly limited, but from the viewpoint of further improving the low heat build-up and crack resistance of the vulcanized rubber, 4 to 4 parts per 100 parts by mass of the rubber component It is preferably 12 parts by mass, more preferably 6 to 10 parts by mass.

[Cobalt-containing compound]
In the present invention, the content of the cobalt-containing compound in the rubber composition is 0.01 parts by mass or less per 100 parts by mass of the rubber component. This means that the rubber composition of the present invention is substantially free of cobalt-containing compounds. This is to reduce the burden on the environment and to comply with various regulations.
From the same point of view, the content of the cobalt-containing compound in the rubber composition is 0.00 parts by mass with respect to 100 parts by mass of the rubber component, that is, the rubber composition does not contain a cobalt-containing compound (is cobalt-free). is preferred.
Examples of cobalt-containing compounds include organic acid cobalt salts and cobalt metal complexes.
Organic acid cobalt salts include, for example, cobalt naphthenate, cobalt stearate, cobalt neodecanoate, cobalt rosinate, cobalt versatate, cobalt tallate, cobalt oleate, cobalt linoleate, cobalt linolenate, cobalt palmitate, and the like. can be mentioned. Cobalt metal complexes include, for example, cobalt acetylacetonate.

(Preparation of rubber composition)
The method for preparing the rubber composition is not particularly limited.
The rubber composition of the present invention can be produced by blending the respective components described above and kneading them using a kneader such as a Banbury mixer, a roll, or an internal mixer.
Here, the blending amount of each component is the same as the amount already described as the content in the rubber composition.
The kneading of each component may be carried out in one step, or may be carried out in two or more steps. For example, when kneading is performed in two stages, the maximum temperature in the first stage of kneading is preferably 130 to 160°C, and the maximum temperature in the second stage is preferably 90 to 120°C.

〔metal〕
The metal contained in the rubber-metal composite of the present invention is a metal whose steel cord surface is coated with three-dimensional plating of copper, zinc, and iron (three-dimensionally plated metal).
Steel cords may be steel monofilaments or multifilaments (twisted cords or aligned bundled cords), and are not limited in shape. When the steel cord is a twisted cord, the twisted structure is not particularly limited, and examples thereof include a single twisted structure, a double twisted structure, a layered structure, and a composite structure consisting of a double twisted structure and a layered structure.

Since the steel cord has a ternary plating layer of copper, zinc, and iron, the components that make up the plating layer can play a role in increasing the adhesion between the rubber and the steel cord. Even when the content of the cobalt compound in the composition is small (0.01 parts by mass or less per 100 parts by mass of the rubber component), high adhesion can be achieved.
The steel cord may be further subjected to surface treatment such as adhesive treatment from the viewpoint of suitably ensuring adhesion to the rubber composition. When using an adhesive treatment, for example, an adhesive treatment such as the trade name "Chemlock" (registered trademark) manufactured by Lord Co. is preferable.

Alternatively, for example, a steel filament having a surface N atom content of 2 atomic % or more and 60 atomic % or less and a surface Cu/Zn ratio of 1 or more and 4 or less can be used. Also, in the metal filament 1, the amount of phosphorus contained as an oxide up to 5 nm of the outermost layer of the filament radially inward of the filament is 7.0 atomic % or less in terms of the total amount excluding the amount of C. are mentioned.

The metal contained in the rubber-metal composite of the present invention is a metal whose steel cord surface is coated with three-dimensional plating of copper, zinc, and iron (three-dimensionally plated metal). More specifically, the metal is a steel cord containing one or more steel filaments as described above, wherein the filaments include a steel filament base material and a coating (plating) that partially or wholly coats the steel filament base material. layer), wherein the coating comprises brass consisting of copper and zinc, the coating is reinforced with iron, the iron is present in the brass as particles, the particles are 10-10000 nano More preferred are steel cords characterized by having metric sizes. More preferably, said particles have a size between 20 and 5000 nanometers. By "iron-reinforced" is meant that the iron is not derived from the filamentary steel substrate.
Here, the brass is composed of copper and zinc, preferably contains at least 63% by mass of copper, the remainder being zinc, more preferably 65% by mass or more of copper, 67% by mass or more of copper.
In addition, the amount of iron in the coating (plating layer) is 1% or more by mass compared to the total mass of brass and iron, and preferably less than 10% by mass. More preferably the amount is at least 3% by weight and less than 9% by weight compared to the total weight of brass and iron.
More preferably, the steel cord is characterized in that said coating is substantially free of zinc-iron alloys.

In the steel cord comprising one or more steel filaments as described above, the amount of phosphorus present on the surface of the filaments, in other words, the amount of phosphorus in the coating (plating layer) is P _s , and the amount of phosphorus on the surface of the filaments is The amount of iron present, in other words the amount of iron in the coating (plating layer) is Fe _s and the amount of (P _s +Fe _s ) is the amount of phosphorus and It is determined by gently etching the surface of the filament with a weak acid that dissolves iron.
(a) About 5 grams of steel cord is weighed, cut into pieces of about 5 cm and introduced into a test tube.
(b) Add 10 ml of 0.01 molar hydrochloric acid HCl.
(c) Shake the sample with the acid solution for 15 seconds.
(d) Measure the amount present in solution by ICP-OES.
Here, ICP-OES means (0;0;0), (2;0.02;1), (5;0.1;2), (10;0.5; 5) Refers to optical emission spectroscopy (ICP-OES) using all standard solutions of (Cu; Fe; Zn) in mg/L.
(e) Shows the mass of (P _s +Fe _s ) per unit of filament steel surface area in milligrams per square meter (mg/m ² ). The result is sometimes called (Fe _s +P _s ).
The amount of phosphorus present on the surface of the filament, in other words, the amount of phosphorus in the coating (plating layer) is 4 mg/m ² or less, but preferably greater than zero to improve adhesion. That is, 0<P _s ≦4 mg/m ² . More preferably, the amount of phosphorus (P _s ) is less than 4 mg/m ² (P _s <4 mg/m ² ).
Higher amounts of phosphorus _Ps reduce adhesion layer growth. The amount of phosphorus _Ps may be lower than 3 mg/m ² , and even better lower than 1.5 mg/m ² .

In a further preferred embodiment, the amount of iron present on the surface of the filaments is preferably 30 mg/m ² or more, more preferably when more than 35 mg/m ² of iron is present on the surface, more than 40 mg/m ² Even more preferred is when the iron is present on the surface.
Also, the mass ratio (Fe _s /P _s ) of the amount of iron present on the surface of the filament to the amount of phosphorus present on the surface of the filament is preferably greater than 27.
The filament surface coating mass SCW is the sum of the masses of brass and iron present in the coating per unit of surface area, the coating mass is expressed in grams per square meter, and the mass ratio [Fe _s /(SCW ×P _s )] is preferably greater than 13.
A method of obtaining steel filaments in which the iron is present as particles in the brass involves wet wire drawing an intermediate wire having a brass coating reinforced with iron particles, followed by wet wire drawing the wire through a smaller die in a lubricant. to a final diameter of 0.28 mm to obtain a steel filament.
Lubricants generally contain high pressure additives containing phosphorus in an organic compound.
Here, the dies to be used may be Set-D dies in which at least the head die is a sintered diamond die and the remaining dies are tungsten carbide dies. The steel cord is preferably wire-drawn with a diamond die.

Since the rubber composition of the present invention can suppress metal corrosion even after a certain period of time has passed since the metal is coated, for example, the product is distributed in a state where the metal cord is coated with the rubber composition, and the product is distributed at the distribution destination. It can be vulcanized to produce a vulcanized rubber-metal composite. In addition, the vulcanized rubber-metal composite produced in this way has suppressed corrosion of the metal, so that the vulcanized rubber-metal adhesion is less likely to be impaired, and the composite is excellent in durability.

As a method for coating the steel cord with the rubber composition, for example, the following methods can be used.
A predetermined number of ternary-plated steel cords are arranged in parallel at predetermined intervals, and the steel cords are coated from above and below with an uncrosslinked rubber sheet having a thickness of about 0.5 mm made of the rubber composition of the present invention. to obtain the precursor. The resulting precursor (unvulcanized rubber-metal composite) is vulcanized. The vulcanization conditions are, for example, a temperature of about 160° C. for about 20 minutes; or a temperature of about 145° C. for about 40 minutes.
The composite of vulcanized rubber and steel cord thus obtained has excellent vulcanized rubber-metal adhesion.

The vulcanized rubber-metal composite of the present invention, which has excellent adhesiveness, is suitably used as a reinforcing material for rubber articles that require strength, such as various automobile tires, crawlers, and hoses. In particular, it is suitably used as a reinforcing member for belts of various automobile radial tires, carcass plies, wire chafers, and the like.

<Tire>
The tire of the invention comprises the vulcanized rubber-metal composite of the invention.
Since the tire of the present invention contains the vulcanized rubber-metal composite of the present invention, it is excellent in crack resistance and low heat build-up.
The method for manufacturing the tire of the present invention is not particularly limited as long as it is a method capable of manufacturing the tire so that the vulcanized rubber-metal composite of the present invention is included in the tire.
In general, a rubber composition containing various components is processed into each member in an unvulcanized stage, and then pasted and molded on a tire molding machine by an ordinary method to form a green tire. The raw tire is heated and pressurized in a vulcanizer to produce a tire. For example, after kneading the rubber composition of the present invention, the resulting rubber composition is used to rubberize three-dimensionally plated steel cords to form unvulcanized belt layers, unvulcanized carcasses, and other unvulcanized belt layers. A tire is obtained by laminating the vulcanized members and vulcanizing the unvulcanized laminate.
The gas to be filled in the tire may be normal air, air with adjusted oxygen partial pressure, or inert gas such as nitrogen, argon, or helium.
The content of cobalt atoms in the tire of the present invention is preferably 1% by mass or less. The content of cobalt atoms in the tire can be said to be 0% by mass if the rubber composition used for tire production does not contain a cobalt-containing compound and the metal of the vulcanized rubber-metal composite does not contain cobalt. The content of cobalt atoms in the tire can be measured, for example, by a method of measuring the element content of each member constituting the tire.

<Crawler, hose>
The crawlers and hoses of the present invention comprise the vulcanized rubber-metal composite of the present invention.
Since the vulcanized rubber-metal composite of the present invention is contained in the chemical product containing the vulcanized rubber-metal composite of the present invention, it is excellent in crack resistance and low heat build-up.
Examples of chemical products include rubber products for chemical products other than tires containing vulcanized rubber-metal composites, and specific examples include rubber products requiring strength such as crawlers and hoses.

<Example 1 and Comparative Examples 1 to 6>
[Preparation of rubber composition]
(Comparative Examples 3-5)
Each component was kneaded according to the compounding composition shown in Tables 1 and 2 to prepare a rubber composition. The details of the components shown in Table 1 are as follows.
Details of the carbon black are shown in Table 1. The content of each component is the content (parts by mass) per 100 parts by mass of the rubber component (natural rubber).

(Example 1 and Comparative Examples 1, 2, and 6)
Each component is kneaded according to the compounding composition shown in Tables 1 and 2 to prepare a rubber composition. The details of the components shown in Table 1 are as follows.
Details of the carbon black are shown in Table 1. The content of each component is the content (parts by mass) per 100 parts by mass of the rubber component (natural rubber).

Natural rubber: RSS#1
Silica: Silica is silica having a CTAB adsorption specific surface area of 230 m ² /g and a BET specific surface area of 236 m ² /g produced by the production method described below. ”
Antiaging agent 6C: N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine, manufactured by Ouchi Shinko Chemical Industry Co., Ltd., trade name "Nocrac 6C"
Zinc white: manufactured by Hakusui Tech Co., Ltd., product name "No. 3 zinc white"
Vulcanization accelerator CBS: N-cyclohexyl-2-benzothiazolylsulfenamide, manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd., trade name "Noccellar CZ-G"
Vulcanizing agent: Sulfur, manufactured by Tsurumi Chemical Co., Ltd., trade name "powder sulfur"

(Method for producing silica)
12 L of a sodium silicate solution with a concentration of 10 g/L (SiO ₂ /Na ₂ O mass ratio of 3.5) were introduced into a 25 L stainless steel reactor. The solution was heated to 80°C. All reactions were carried out at this temperature. Sulfuric acid having a concentration of 80 g/L was introduced with stirring (300 rpm, propeller stirrer) until the pH reached a value of 8.9.
A sodium silicate solution having a concentration of 230 g/L (SiO ₂ /Na ₂ O mass ratio of 3.5) was added at a rate of 76 g/min and sulfuric acid having a concentration of 80 g/L was added to bring the pH of the reaction mixture to 8.9. were simultaneously introduced into the reactor over 15 minutes at a rate set to maintain a value of . A sol of agglomerated particles was then obtained. The sol was collected and rapidly cooled using a copper coil with circulating cold water. The reactor was quickly cleaned.

4 L of pure water was introduced into this 25 L reactor. Sulfuric acid having a concentration of 80 g/L was introduced until a pH of 4 was reached. Simultaneous addition of the cooled sol at a flow rate of 195 g/min and sulfuric acid (having a concentration of 80 g/L) at a flow rate allowing the pH to be set to 4 was carried out over 40 minutes. A maturation step lasting 10 minutes was performed.
40 minutes after the simultaneous sol/sulfuric acid addition, sodium silicate at a flow rate of 76 g/min for 20 minutes (the same sodium silicate as for the first simultaneous addition) and the pH of the reaction mixture is maintained at 4. There was a simultaneous addition of sulfuric acid (80 g/L) at a flow rate set as follows. After 20 minutes the acid flow was stopped when the pH was 8.

A new co-addition was carried out over 60 minutes at a sodium silicate flow rate of 76 g/min (same sodium silicate as for the first co-addition) and sulfuric acid (80 g) set to maintain the pH of the reaction mixture at a value of 8. /L). The stirring speed was increased when the mixture became very viscous.
After this simultaneous addition, the reaction mixture was brought to a pH of 4 with sulfuric acid having a concentration of 80 g/L for 5 minutes. The mixture was aged at pH 4 for 10 minutes. The slurry was filtered and washed under vacuum (15% cake solids) and after dilution the resulting cake was mechanically broken up. The resulting slurry was spray dried in a turbine spray dryer to obtain sample silica.

(Physical properties of carbon black)
Various physical properties of carbon black shown in Table 1 were obtained by the following methods.
(i) Compressed dibutyl phthalate absorption (24M4DBP)
24M4DBP absorption (cm ³ /100 g) was measured according to ISO 6894.

(ii) CTAB adsorption specific surface area The CTAB adsorption specific surface area (m ² /g) was measured by a method based on JIS K 6217-3:2001 (Determination of specific surface area - CTAB adsorption method).

(iii) Aggregate distribution (centrifugal sedimentation method)
As a measuring device, a Disk Centrifuge Photosedimentometer (DCP) "BI-DCP Particle sizer" (manufactured by Brookhaven) was used. In addition, it was measured according to ISO/CD 15825-3 as follows.
Add 0.05 to 0.1% by mass of carbon black to a 25% by volume ethanol aqueous solution to which a small amount of surfactant is added, and perform ultrasonic treatment (1/2 inch oscillation tip, output 50 W) to completely It was dispersed to obtain a dispersion liquid. 17.5 mL of distilled water was added as a sedimentation liquid (spin liquid), and the rotation speed of the rotating disk was set to 8,000 rpm. Simultaneously with the addition of the dispersion liquid, the recorder was operated to optically measure the amount of carbon black aggregates passing through a fixed point near the outer circumference of the rotating disk due to sedimentation, and the absorbance (frequency) was plotted as a continuous curve with respect to time. Recorded. The sedimentation time was converted into the Stokes equivalent diameter d by the following Stokes general formula (A) to obtain a curve corresponding to the Stokes equivalent diameter of aggregates and their frequency.
d=K/√t (A)

In the above formula (A), d is the Stokes equivalent diameter (nm) of carbon black aggregates passing through the optical measurement point of the rotating disk t minutes after the start of precipitation. The constant K is a value determined by the temperature and viscosity of the spin liquid during measurement, the density difference from carbon black (assuming that the true density of carbon black is 1.86 g/cm ³ ), and the rotation speed of the rotating disk. . In this example and comparative example, 17.5 mL of distilled water was used as the spin liquid, the measurement temperature was 23.5° C., and the disk rotation speed was 8,000 rpm, so the constant K was 261.75. From these measurement results, the Stokes diameter Dst (nm), the half width ΔD50 (nm), and the ratio (ΔD50/Dst) were obtained.
The definitions of the Stokes diameter Dst and the half width ΔD50 are as follows.

Stokes diameter Dst: Refers to the Stokes equivalent diameter showing the highest frequency in the correspondence curve between the Stokes equivalent diameter of the aggregate and its frequency.
Half-value width ΔD50: The width of the distribution when the frequency is half the height of the maximum point in the correspondence curve between the Stokes-equivalent diameter d of the aggregate and its frequency.

[Preparation of vulcanized rubber-metal composite]
(Example 1, Comparative Examples 1 and 2)
A steel cord whose surface is coated with ternary plating of copper, zinc, and iron and contains about 1% by mass of iron can be used as the metal. This ternary plated steel cord is obtained using a Set-D die, and more specifically, manufactured by the method described in paragraphs [0065] to [0070] of WO 2020/156967. .
The ternary plated steel cord is coated with the prepared rubber composition to produce an unvulcanized rubber-metal composite (unvulcanized steel cord topping product).
The unvulcanized rubber-metal composite is vulcanized to produce a vulcanized rubber-metal composite.

The amount of iron Fe _s and the amount of phosphorus P _s in the coating (plating layer) of the ternary plated steel cord is determined by gently etching the surface of the filament of the steel cord with hydrochloric acid. Specifically, it is measured according to the following procedures (a) to (d).
(a) 5 grams of steel cord is weighed, cut into 5 cm pieces and introduced into a test tube.
(b) Add 10 ml of 0.01 M hydrochloric acid HCl to the test tube.
(c) Shake the sample for 15 seconds.
(d) Measure the amount present in the hydrochloric acid solution by ICP-OES.
Here, ICP-OES means (0;0;0), (2;0.02;1), (5;0.1;2), (10;0.5; 5) Refers to optical emission spectroscopy (ICP-OES) using all standard solutions of (Cu; Fe; Zn) in mg/L.
The iron content Fe _s in the coating (plating layer) of the ternary plated steel cord is 32.2 mg/m ² , and the phosphorus content P _s is 1.5 mg/m ² .

(Comparative Examples 3-5)
A steel cord whose surface was coated with brass plating (copper-zinc plating) was used as the metal.
The brass-plated steel cord was coated with the prepared rubber composition to produce an unvulcanized rubber-metal composite (unvulcanized steel cord topping product).
The unvulcanized rubber-metal composite was vulcanized to prepare a vulcanized rubber-metal composite.

(Comparative Example 6)
A steel cord whose surface is coated with brass plating (copper-zinc plating) is used as the metal.
The brass-plated steel cord is coated with the prepared rubber composition to produce an unvulcanized rubber-metal composite (unvulcanized steel cord topping product).
The unvulcanized rubber-metal composite is vulcanized to produce a vulcanized rubber-metal composite.

<Evaluation>
1. Adhesion (1) Initial Adhesion A steel cord is pulled out from a vulcanized rubber-metal composite after vulcanization is performed under half the vulcanization time of normal vulcanization conditions (time for TC90 plus 5 minutes). The coating state of the vulcanized rubber adhering to the steel cord was observed by visual observation. The coating amount of the vulcanized rubber of the examples is indicated by an index. Table 2 shows the results. The acceptable range is 100 or more.
TC90 means the time for a specific rubber to reach 90% of the maximum torque on the rheometer curve at the vulcanization temperature.

(2) Wet heat deterioration The vulcanized rubber-metal composite immediately after vulcanization is stored in a steam environment at 120°C for 2 days, and the steel cord is pulled out from the vulcanized rubber-metal composite after storage. The coating state of the vulcanized rubber adhering to the steel cord was observed by visual observation. The coating amount of the vulcanized rubber of the examples is indicated by an index. Table 2 shows the results. The allowable range is 120 or more.

2. Crack Resistance Vulcanized rubber obtained by vulcanizing the rubber compositions of Examples and Comparative Examples at 160° C. for 15 minutes is deteriorated in an air atmosphere at 100° C. for 24 hours. After that, the vulcanized rubber is punched into a dumbbell shape to obtain a test piece. A test piece with a pre-crack of 1 mm in the center is subjected to a stroke of 5 Hz under the conditions of 80 ° C., a distance between chucks of 20 mm, and a constant stress with a fatigue tester, and the number of times until the test piece completely breaks is counted. Measure.
Regarding the evaluation, the number of times until the vulcanized rubber test piece of the example fractures is expressed as an index when the number of times until the vulcanized rubber test piece of Comparative Example 1 fractures is set to 100. Table 2 shows the results. The larger the index value, the longer the life, indicating that the vulcanized rubber is excellent in crack resistance. The acceptable range is 100 or more.

3. Low heat buildup Vulcanized rubber test pieces obtained by vulcanizing the rubber compositions of Examples and Comparative Examples at 160°C for 15 minutes were measured using a viscoelasticity measuring device (manufactured by Rheometrics) at a temperature of 60°C, Measure tan δ at a strain of 5% and a frequency of 15 Hz.
Regarding the evaluation, the tan δ of the vulcanized rubber test piece of Comparative Example 1 is assumed to be 100, and the tan δ of the vulcanized rubber test piece of the example is indicated by the following formula. Table 2 shows the results. The smaller the index value, the smaller the hysteresis loss and the better the low heat build-up. The acceptable range is less than 100.
Pyrogenic index = {(tan δ of each test piece)/(tan δ of test piece of Comparative Example 1)} × 100

In Table 2, A in the "steel cord type" column means that the steel cord surface is coated with ternary plating of copper, zinc, and iron, and B means that the steel cord surface is brass-plated ( copper-zinc plating).

The vulcanized rubber-metal composite of Example 1 exhibits well-balanced and excellent effects in terms of crack resistance, low heat build-up and adhesiveness compared to the vulcanized rubber-metal composites of Comparative Examples 1-6. Recognize.
In the example of Patent Document 2 (WO 2020/156967), as shown in FIG. 1 (Fig. 3a of Patent Document 2), as the amount of iron in the coating by ternary plating increases, Vulcanized rubber-metal adhesion is reduced. On the other hand, the vulcanized rubber-metal composite according to Example 1 can improve the vulcanized rubber-metal adhesion, so regardless of the increase or decrease in the amount of iron in the coating, vulcanization of a certain level or more Rubber-to-metal adhesion can be achieved.
In FIG. 1, "1-W" etc. on the horizontal axis refer to the samples shown in Table II of paragraph number [0075] of Patent Document 2, and the larger the number, the larger the amount of iron in the coating. Also, the Z-Score on the vertical axis indicates the superiority or inferiority of adhesion, and the larger the value, the better the vulcanized rubber-metal adhesion.

According to the present invention, it is possible to provide a vulcanized rubber-metal composite that is excellent in vulcanized rubber-metal adhesion, crack resistance and low heat build-up. This vulcanized rubber-metal composite is suitably used as a reinforcing material for rubber articles that require strength, such as various automobile tires, crawlers, and hoses. Among others, it is suitably used as a reinforcing member for various automotive radial tire belts, carcass plies, wire chafers and the like.

Claims (18)

A vulcanized rubber-metal composite comprising a metal and a vulcanized rubber covering the metal,
The vulcanized rubber is a vulcanized rubber of a rubber composition containing a rubber component, carbon black, and silica, and having a cobalt-containing compound content of 0.01 parts by mass or less with respect to 100 parts by mass of the rubber component. can be,
The metal is a vulcanized rubber-metal composite in which the surface of the steel cord is coated with ternary plating of copper, zinc, and iron. The vulcanized rubber-metal composite according to claim 1, wherein the amount of said iron in said coating is 1% by mass or more and less than 10% by mass of the total mass of said copper, said zinc and said iron. 3. The vulcanized rubber-metal composite according to claim 1 or 2, wherein the amount of phosphorus in the coating is more than 0 mg/m ² and not more than 4 mg/m ² . The vulcanized rubber-metal composite according to any one of claims 1 to 3, wherein the steel cord is wire-drawn with a diamond die. The additive according to any one of claims 1 to 4, wherein the ratio (c:s) of the carbon black content c and the silica content s is 60:40 to 85:15 on a mass basis. Sulfur rubber-metal composite. The vulcanized rubber-metal composite according to any one of claims 1 to 5, wherein the carbon black has a cetyltrimethylammonium bromide adsorption specific surface area of 110 to 160 m ² /g. The carbon black has a peak half width ΔD50 of 60 nm or less including the Stokes equivalent diameter Dst that shows the highest frequency in the aggregate distribution obtained by centrifugal sedimentation, and the ratio of the ΔD50 to the Dst (ΔD50/ Dst) is 0.95 or less, the vulcanized rubber-metal composite according to any one of claims 1 to 6. The vulcanized rubber-metal composite according to any one of claims 1 to 7, wherein the silica has a cetyltrimethylammonium bromide adsorption specific surface area of 200 m ² /g or more. The vulcanized rubber-metal composite according to any one of claims 1 to 8, wherein the total content of said carbon black and said silica is 30 to 80 parts by mass with respect to 100 parts by mass of said rubber component. The vulcanized rubber-metal composite according to any one of claims 1 to 9, wherein the rubber composition contains a vulcanizing agent and a vulcanization accelerator. The vulcanized rubber-metal composite according to any one of claims 1 to 10, wherein the carbon black has a compressed dibutyl phthalate absorption of 80 to 110 cm ³ /100 g. The vulcanized rubber-metal composite according to any one of claims 1 to 11, wherein the silica content is 5 to 25 parts by mass with respect to 100 parts by mass of the rubber component. The vulcanized rubber-metal composite according to any one of claims 1 to 12, wherein the content of the cobalt-containing compound in the rubber composition is 0.00 parts by mass with respect to 100 parts by mass of the rubber component. . The ratio (c:s) of the carbon black content c and the silica content s, based on mass, is 76:24 to 85:15. Vulcanized rubber-metal composite. A tire comprising the vulcanized rubber-metal composite according to any one of claims 1-14. 16. The tire according to claim 15, wherein the content of cobalt atoms is 1% by mass or less. A hose comprising the vulcanized rubber-metal composite according to any one of claims 1-14. A crawler comprising the vulcanized rubber-metal composite according to any one of claims 1-14.

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