JP7490355B2 - Vulcanized rubber-metal composites as well as tires, hoses, conveyor belts, and crawlers - Google Patents

Description

The present invention relates to vulcanized rubber-metal composites as well as tires, hoses, conveyor belts, and crawlers.

As a rubber composition with excellent initial adhesion to metal, adhesion resistance to wet heat, and adhesion after being left to treat, a rubber composition has been disclosed that is made by compounding 0.02 to 10 parts by mass of a nitrogen-containing cyclic compound with respect to 100 parts by mass of the rubber component, and that is characterized in that the nitrogen-containing cyclic compound does not have a benzene ring or a mercapto group (see, for example, Patent Document 1).

JP 2014-231580 A

However, Patent Document 1 does not examine the heat-resistant adhesiveness when the cobalt compound is omitted.

In view of the above circumstances, the present invention aims to provide a vulcanized rubber-metal composite in which vulcanized rubber of a rubber composition that is substantially free of cobalt compounds is used as a metal-coating rubber, the vulcanized rubber-metal composite having excellent oxygen-resistant adhesion and heat-resistant adhesion, and a tire, hose, conveyor belt, and crawler that use the same and have excellent durability, and the task of achieving this objective.

<1> A vulcanized rubber-metal composite comprising vulcanized rubber and a metal, the vulcanized rubber and the metal being bonded to each other,
The vulcanized rubber is
A rubber component,
zinc oxide having a nitrogen adsorption specific surface area of 40 to 100 m ² /g, in an amount of 2 parts by mass or more per 100 parts by mass of the rubber component;
and an organic thiosulfate compound,
a vulcanized rubber of a rubber composition having a cobalt-containing compound content of 0.1 parts by mass or less per 100 parts by mass of the rubber component,
The vulcanized rubber-metal composite is a ternary plated metal plated with three types of metal.

<2> The vulcanized rubber-metal composite according to <1>, wherein the content of the organic thiosulfate compound in the rubber composition is 0.1 parts by mass or more and less than 2.0 parts by mass per 100 parts by mass of the rubber component.
<3> The vulcanized rubber-metal composite according to <1> or <2>, wherein the rubber composition further contains 0.1 parts by mass or more and 2.0 parts by mass or less of a bismaleimide compound per 100 parts by mass of the rubber component.
<4> The vulcanized rubber-metal composite according to any one of <1> to <3>, wherein the rubber composition further contains 0.6 parts by mass or more and 2.0 parts by mass or less of stearic acid per 100 parts by mass of the rubber component.

<5> The vulcanized rubber-metal composite according to any one of <1> to <4>, wherein the rubber composition contains two types of zinc oxide having different nitrogen adsorption specific surface areas, and the total content of the zinc oxide is 7.6 parts by mass or more per 100 parts by mass of the rubber component.
<6> The vulcanized rubber-metal composite according to <5>, wherein the two types of zinc oxide having different nitrogen adsorption specific surface areas include zinc oxide having a nitrogen adsorption specific surface area of 40 to 100 m ² /g and zinc oxide having a nitrogen adsorption specific surface area of 1.0 to 10 m ² /g, and the content a of the zinc oxide having a nitrogen adsorption specific surface area of 40 to 100 m ² /g in the rubber composition and the content b of the zinc oxide having a nitrogen adsorption specific surface area of 1.0 to 10 m ² /g in the rubber composition satisfy the relationship, on a mass basis, of [a/(a + b)] x 100 = 20 or more and less than 100.
<7> The vulcanized rubber-metal composite according to any one of <4> to <6>, wherein a total amount c of zinc oxide in the rubber composition and a content d of stearic acid in the rubber composition satisfy a relationship of [c/(c+d)]×100=75 or more and less than 100, on a mass basis.

<8> The vulcanized rubber-metal composite according to any one of <1> to <7>, wherein the three kinds of metals are copper, cobalt, and zinc.
<9> The vulcanized rubber-metal composite according to any one of <1> to <8>, wherein the amount of phosphorus element present in a surface layer region extending from the surface of the metal to a depth of 5 nm inward is 3.0 atomic % or less.
<10> The vulcanized rubber-metal composite according to <8> or <9>, wherein the ratio of elements constituting the ternary plating metal is 61 to 70 mass% copper and 1.0 to 5.0 mass% cobalt.

<11> The vulcanized rubber-metal composite according to any one of <1> to <10>, in which the organic thiosulfate compound is hexamethylene bisthiosulfate disodium salt dihydrate.

<12> A tire comprising the vulcanized rubber-metal composite according to any one of <1> to <11>.
<13> A hose comprising the vulcanized rubber-metal composite according to any one of <1> to <11>.
<14> A crawler comprising the vulcanized rubber-metal composite according to any one of <1> to <11>.
<15> A conveyor belt comprising the vulcanized rubber-metal composite according to any one of <1> to <11>.

According to the present invention, it is possible to provide a vulcanized rubber-metal composite in which a vulcanized rubber of a rubber composition that is substantially free of cobalt compounds is used as a metal-coating rubber, and the vulcanized rubber-metal composite has excellent oxygen-resistant adhesion and heat-resistant adhesion, as well as tires, hoses, conveyor belts, and crawlers that use the same and have excellent durability.

The present invention will be described in detail below with reference to embodiments thereof. In the following description, the expression "A to B" indicating a numerical range indicates a numerical range including the endpoints A and B, and indicates "A or more and B or less" (when A<B) or "A or less and B or more" (when A>B).
Furthermore, 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 that contains vulcanized rubber and a metal, and in which the vulcanized rubber and the metal are bonded to each other.
Here, the vulcanized rubber is a vulcanized rubber of a rubber composition containing a rubber component, zinc oxide having a nitrogen adsorption specific surface area of 40 to 100 ^m2 /g in an amount of 2 parts by mass or more per 100 parts by mass of the rubber component, and an organic thiosulfate compound, and the content of a cobalt-containing compound is 0.1 part by mass or less per 100 parts by mass of the rubber component.
Such vulcanized rubber may be referred to as "the vulcanized rubber of the present invention."
The rubber composition that is the base of the vulcanized rubber of the present invention may be 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 ternary plated metal plated with three different metal species.

The reason why the vulcanized rubber-metal composite of the present invention has excellent oxygen-resistant adhesion and heat-resistant adhesion is unclear, but it is believed to work as follows. That is, active zinc oxide and stearic acid are involved in the adhesive layer forming reaction, and a good adhesive layer is formed during vulcanization, which is thought to be an adhesive layer that is superior to oxygen and heat. As a result, it was found that the above-mentioned effects can be achieved by configuring the rubber composition of the present invention as described above.
The rubber composition and metal of the present invention will be described below.

[Rubber composition]
The rubber composition of the present invention includes a rubber component, zinc oxide having a nitrogen adsorption specific surface area of 40 to 100 m ² /g in an amount of 2 parts by mass or more per 100 parts by mass of the rubber component, and an organic thiosulfate compound, and the content of a cobalt-containing compound is 0.1 part by mass or less per 100 parts by mass of the rubber component.
The rubber composition of the present invention may further contain a filler, a vulcanization accelerator, stearic acid, zinc oxide having a nitrogen adsorption specific surface area different from the above range, and the like.

(Rubber component)
The rubber component is usually a diene rubber.
Examples of diene rubbers include isoprene rubber, polybutadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), and modified rubbers thereof. The rubber component may contain a non-diene rubber to the extent that the effects of the present invention are not impaired.
The rubber component may be used alone or in combination of two or more kinds.
Among the above, from the viewpoint of further improving the oxygen-resistant adhesion and heat-resistant adhesion of the vulcanized rubber-metal composite, it is preferable that the rubber component contains an isoprene-based rubber.

Examples of isoprene-based rubbers include natural rubber (NR), polyisoprene rubber (IR), butadiene-isoprene copolymer rubber (BIR), styrene-isoprene copolymer rubber (SIR), styrene-butadiene-isoprene copolymer rubber (SBIR), and modified rubbers thereof. Only one type of isoprene-based rubber may be used, or two or more types may be mixed and used.
Among the above, from the viewpoint of further improving the oxygen-resistant adhesion and heat-resistant adhesion of the vulcanized rubber-metal composite, the isoprene-based rubber is preferably one or more selected from the group consisting of natural rubber and polyisoprene rubber, and natural rubber is more preferable.

The content of isoprene-based rubber in the rubber component is preferably more than 50% by mass, more preferably 70% by mass or more, more preferably 90% by mass or more, and may be 100% by mass.

(Zinc oxide)
The rubber composition of the present invention contains 2 parts by mass or more of zinc oxide with respect to 100 parts by mass of the rubber component and having a nitrogen adsorption specific surface area of 40 to 100 m ² /g.
The nitrogen adsorption specific surface area of zinc oxide is the nitrogen adsorption specific surface area (N ₂ SA) measured in accordance with the BET method specified in ASTM D4567-03 (2007), and is sometimes referred to as the "BET specific surface area."
In the present invention, zinc white having a fine particle size with a nitrogen adsorption specific surface area of 40 m ² /g or more is called active zinc white.
If the rubber composition does not contain 2 parts by mass or more of active zinc white per 100 parts by mass of the rubber component, the vulcanization activity of the rubber composition cannot be improved, and a vulcanized rubber-metal composite having excellent oxygen-resistant adhesion and heat-resistant adhesion cannot be obtained.
Moreover, when the nitrogen adsorption specific surface area of the active zinc white is 100 m ² /g or less, over-vulcanization of the rubber composition can be suppressed and the heat-resistant adhesion of the vulcanized rubber-metal composite can be improved. The nitrogen adsorption specific surface area of the active zinc white is more preferably 40 to 90 m ² /g, and even more preferably 40 to 80 m ² /g.

The rubber composition of the present invention preferably contains two types of zinc oxide having different nitrogen adsorption specific surface areas, and the total zinc oxide content c is 7.6 parts by mass or more per 100 parts by mass of the rubber component. More specifically, the zinc oxide further contains zinc oxide having a larger particle size than the active zinc oxide in addition to the active zinc oxide, and the total zinc oxide content c in the rubber composition including the active zinc oxide is preferably 7.6 parts by mass or more per 100 parts by mass of the rubber component.
When the content c is 7.6 parts by mass or more per 100 parts by mass of the rubber component, the vulcanization activity of the rubber composition can be further improved, and the oxygen-resistant adhesion and heat-resistant adhesion of the vulcanized rubber-metal composite can be further improved.
The total amount c of zinc oxide in the rubber composition is more preferably 7.6 to 17 parts by mass, further preferably 7.6 to 15 parts by mass, and even more preferably 8.5 to 12 parts by mass, per 100 parts by mass of the rubber component.

The two types of zinc oxide having different nitrogen adsorption specific surface areas preferably include zinc oxide (active zinc oxide) having a nitrogen adsorption specific surface area (BET specific surface area) of 40 to 100 m ² /g and zinc oxide having a nitrogen adsorption specific surface area (BET specific surface area) of 1.0 to 10 m ² /g.
Zinc oxide having a nitrogen adsorption specific surface area of 1.0 to 10 m ² /g is preferably 1.5 m ² /g or more, and more preferably 2.0 m ² /g or more, from the viewpoint of improving vulcanization activity.
Activated zinc oxide having a nitrogen adsorption specific surface area of 40 to 100 m ² /g can be produced by a wet method, while ordinary zinc oxide having a nitrogen adsorption specific surface area of 1.0 to 10 m ² /g can be produced by a dry method.

It is preferable that the content a of zinc white having a nitrogen adsorption specific surface area of 40 to 100 m ² /g in the rubber composition and the content b of zinc white having a nitrogen adsorption specific surface area of 1.0 to 10 m ² /g in the rubber composition satisfy the relationship of [a/(a+b)]×100=20 to less than 100 by mass. This means that the content of active zinc white in the total amount of active zinc white and normal zinc white having a nitrogen adsorption specific surface area of 1.0 to 10 m ² /g is 20 to less than 100 by mass. By having [a/(a+b)]×100 being 20 to less than 100, the vulcanization activity can be further improved.
From the viewpoint of further improving the vulcanization activity, [a/(a+b)]×100 is more preferably 25 or more, even more preferably 30 or more, and even more preferably 35 or more, and is more preferably 90 or less, even more preferably 80 or less, even more preferably 70 or less, and even more preferably 60 or less.

(Organic Thiosulfate Compounds)
The rubber composition of the present invention contains an organic thiosulfate compound.
If the rubber composition does not contain an organic thiosulfate compound, it is not possible to obtain a vulcanized rubber-metal composite having excellent heat-resistant adhesion between the metal and the vulcanized rubber.
The organic thiosulfate compounds used in the present invention can be represented by the following formula:
_MO3S -S-( _CH2 ) _m -S- _SO3M
In the formula, m is 3 to 10, and M is lithium, potassium, sodium, magnesium, calcium, barium, zinc, nickel or cobalt. The organic thiosulfate compound may contain water of crystallization.

In terms of the effects of the present invention, m is preferably an integer of 3 to 10, and more preferably an integer of 3 to 6.
In terms of the effects of the present invention, M is preferably potassium or sodium. The organic thiosulfate compound may contain water of crystallization in the molecule, and specific examples thereof include sodium salt monohydrate and sodium salt dihydrate.
In terms of the effects of the present invention, the organic thiosulfate compound is preferably a derivative of sodium thiosulfate, for example, hexamethylene bisthiosulfate disodium salt dihydrate.

The content of the organic thiosulfate compound in the rubber composition is preferably 0.1 to 5.0 parts by mass, more preferably 0.3 to 4.0 parts by mass, even more preferably 0.5 to 3.0 parts by mass, even more preferably 0.6 to 2.0 parts by mass, and even more preferably less than 2.0 parts by mass, per 100 parts by mass of the rubber component.

(Bismaleimide compounds)
The rubber composition of the present invention preferably contains 0.1 parts by mass or more and 2.0 parts by mass or less of a bismaleimide compound per 100 parts by mass of the rubber component.
When the rubber composition contains 0.1 parts by mass or more and 2.0 parts by mass or less of the bismaleimide compound per 100 parts by mass of the rubber component, the amount of zinc compounds produced in the adhesive layer can be further suppressed, and the oxygen-resistant adhesion and heat-resistant adhesion of the vulcanized rubber-metal composite can be further improved.
The content of the bismaleimide compound in the rubber composition is preferably 0.3 to 1.8 parts by mass, more preferably 0.5 to 1.5 parts by mass, and further preferably 0.6 to 1.3 parts by mass, per 100 parts by mass of the rubber component.

Examples of the bismaleimide compound include N,N'-1,2-ethylene bismaleimide, N,N'-1,2-propylene bismaleimide, 4,4'-bismaleimide diphenylmethane, N,N'-m-phenylene bismaleimide, N,N'-(4,4-diphenyl-methane)bismaleimide, bis(3-ethyl-5-methyl-4-maleimidophenyl)methane, 2,2'-bis[4-(4-maleimidophenoxy)phenyl]propane, m-phenylenebis(methylene)bismaleimide, m-phenylenebis(methylene)biscitraconimide, and 1,1'-(methylenedi-4,1-phenylene)bismaleimide.
Among these, N,N'-m-phenylene bismaleimide and N,N'-(4,4-diphenyl-methane) bismaleimide are more preferred.
The bismaleimide compounds may be used alone or in combination of two or more kinds.

(stearic acid)
The rubber composition of the present invention preferably contains 0.6 parts by mass or more and 2.0 parts by mass or less of stearic acid per 100 parts by mass of the rubber component.
When the rubber composition contains 0.6 parts by mass or more and 2.0 parts by mass or less of stearic acid per 100 parts by mass of the rubber component, the oxygen-resistant adhesion and heat-resistant adhesion of the vulcanized rubber-metal composite can be further improved.
The content d of stearic acid in the rubber composition is preferably 0.6 to 1.8 parts by mass, more preferably 0.6 to 1.5 parts by mass, and further preferably 0.6 to 1.3 parts by mass, based on 100 parts by mass of the rubber component.

It is preferable that the total amount c of zinc oxide in the rubber composition and the content d of stearic acid satisfy the relationship, on a mass basis, of [c/(c+d)]×100=75 or more and less than 100. This means that the total content of zinc oxide in the total amount of all zinc oxide and stearic acid is 75% by mass or more and less than 100% by mass. When the zinc oxide in the rubber composition consists of active zinc oxide and ordinary zinc oxide having a nitrogen adsorption specific surface area of 1.0 to 10 m ² /g, the total amount c of zinc oxide = a + b.
The oxygen-resistant adhesion and heat-resistant adhesion of the vulcanized rubber-metal composite can be further improved by ensuring that [c/(c+d)]×100 is at least 75 and less than 100. From this viewpoint, [c/(c+d)]×100 is more preferably at least 80, even more preferably at least 85, and is more preferably at most 99, even more preferably at most 95, on a mass basis.

(Cobalt-containing compounds)
The rubber composition of the present invention has a cobalt-containing compound content of 0.1 part by mass or less based on 100 parts by mass of the rubber component. This means that the rubber composition of the present invention is substantially free of a cobalt-containing compound.
Examples of the cobalt-containing compound include organic acid cobalt salts and cobalt metal complexes.
Examples of the organic acid cobalt salts include cobalt naphthenate, cobalt stearate, cobalt neodecanoate, cobalt rosinate, cobalt versatate, cobalt tall oil acid, cobalt oleate, cobalt linoleate, cobalt linolenate, cobalt palmitate, etc. Examples of the cobalt metal complexes include cobalt acetylacetonate.

Conventionally, the adhesive effect between vulcanized rubber and metal was obtained by using a cobalt-containing compound, but since the rubber composition of the present invention has the composition already described, even if the rubber composition does not contain a cobalt-containing compound, it has excellent adhesiveness between vulcanized rubber and metal, and also has excellent heat-resistant adhesiveness. Furthermore, since the rubber composition does not contain a cobalt-containing compound, metal corrosion can be suppressed and the environmental burden can be reduced.

(filler)
The rubber composition of the present invention preferably contains a filler from the viewpoint of improving the mechanical strength of the vulcanized rubber. The filler is preferably a reinforcing filler that reinforces the rubber composition.
Examples of reinforcing fillers include carbon black; metal oxides such as silica, alumina, titania, and zirconia; metal carbonates such as magnesium carbonate and calcium carbonate; and aluminum hydroxide.
The filler may be used alone or in combination of two or more kinds.

The content of the filler in the rubber composition is preferably 30 to 70 parts by mass per 100 parts by mass of the rubber component.
By containing 30 to 70 parts by mass of a filler per 100 parts by mass of the rubber component in the rubber composition, the reinforcing properties of the vulcanized rubber of the present invention are improved, and a vulcanized rubber-metal composite having excellent heat-resistant adhesion between the metal and the vulcanized rubber can be obtained.
From the viewpoint of further improving the oxygen-resistant adhesion and heat-resistant adhesion of the vulcanized rubber-metal composite, the content of the filler in the rubber composition is preferably 40 to 69 parts by mass, more preferably 45 to 68 parts by mass, and even more preferably 50 to 68 parts by mass, per 100 parts by mass of the rubber component.

From the viewpoint of improving the reinforcing properties of the vulcanized rubber of the present invention and obtaining a vulcanized rubber-metal composite having excellent heat-resistant adhesion between the metal and the vulcanized rubber, the filler preferably contains carbon black.
The type of carbon black is not particularly limited and can be appropriately selected according to the purpose. Carbon black is preferably, for example, FEF, SRF, HAF, ISAF, and SAF grade, more preferably HAF, ISAF, and SAF grade, and even more preferably HAF grade. Carbon black may be used alone or in combination of two or more kinds.
The content of carbon black in the filler is preferably more than 50% by mass, more preferably 70% by mass or more, more preferably 90% by mass or more, and may be 100% by mass.

(sulfur)
The rubber composition of the present invention preferably contains sulfur.
The sulfur is not particularly limited, and examples thereof include powdered sulfur, precipitated sulfur, colloidal sulfur, surface-treated sulfur, insoluble sulfur, etc. The insoluble sulfur may be an oil-treated product containing oil.
From the viewpoint of further improving the heat-resistant adhesion between the vulcanized rubber and metal and further improving the durability of the vulcanized rubber-metal composite, the content of sulfur in the rubber composition is preferably 3.0 to 10.0 parts by mass, more preferably 4.0 to 9.0 parts by mass, and even more preferably 5.0 to 8.0 parts by mass, per 100 parts by mass of the rubber component. In the case of sulfur containing components other than sulfur such as an oil treated product, the content of sulfur in the rubber composition means the amount of sulfur itself excluding the components other than sulfur.

(Vulcanization accelerator)
The rubber composition of the present invention preferably contains a vulcanization accelerator in order to further accelerate the vulcanization of the rubber component.
Specific examples of vulcanization accelerators include thiuram-based, guanidine-based, aldehyde-amine-based, aldehyde-ammonia-based, thiazole-based, sulfenamide-based, thiourea-based, dithiocarbamate-based, xanthate-based, etc. Only one type of vulcanization accelerator may be used, or two or more types may be used.
Among the above, sulfenamide-based adhesives are preferred from the viewpoint of further improving the heat-resistant adhesion between vulcanized rubber and metal.
The content of the vulcanization accelerator in the rubber composition is preferably 0.1 to 3 parts by mass, more preferably 0.2 to 2 parts by mass, and even more preferably 0.3 to 1.2 parts by mass, per 100 parts by mass of the rubber component, from the viewpoints of further improving the heat-resistant adhesion between the vulcanized rubber and metal and further improving the durability of the vulcanized rubber-metal composite.

(Vulcanization Retarder)
The rubber composition of the present invention may contain a vulcanization retarder.
By including the vulcanization retarder in the rubber composition, it is possible to suppress rubber burning caused by overheating of the rubber composition during preparation of the rubber composition, and also to improve the scorch stability of the rubber composition, thereby making it easier to extrude the rubber composition from a kneader.
Examples of the vulcanization retarder include phthalic anhydride, benzoic acid, salicylic acid, N-nitrosodiphenylamine, N-(cyclohexylthio)-phthalimide, sulfonamide derivatives, diphenylurea, bis(tridecyl)pentaerythritol diphosphite, etc. As the vulcanization retarder, a commercially available product may be used, for example, Monsanto's product name "Santoguard PVI" [N-(cyclohexylthio)-phthalimide], etc.
Among the above, N-(cyclohexylthio)-phthalimide is preferably used as the vulcanization retarder.
When a vulcanization retarder is used, from the viewpoint of suppressing rubber burning of the rubber composition without interfering with the vulcanization reaction and improving scorch stability, the content of the vulcanization retarder in the rubber composition is preferably 0.05 to 1.0 part by mass, more preferably 0.05 to 0.7 part by mass, and even more preferably 0.05 to 0.5 part by mass, per 100 parts by mass of the rubber component.

(Alkylphenol resin)
The rubber composition of the present invention preferably contains an alkylphenol resin.
The alkylphenol resin refers to a phenol resin having an alkyl group on the phenol skeleton of the phenol resin. The number of alkyl groups of the alkylphenol resin (the number of groups bonded to the phenol skeleton) and the number of carbon atoms of the alkyl group are not particularly limited, but the number of alkyl groups is usually 1 to 3, and the number of carbon atoms per alkyl group is preferably 1 to 15, and more preferably 5 to 10. The alkyl group may be linear, branched, or cyclic. The rubber composition may contain one type of alkylphenol resin alone, or may contain a mixture of multiple types.
From the viewpoint of further improving the heat-resistant adhesion between the vulcanized rubber and metal, the content of the alkylphenol resin in the rubber composition is preferably 0.1 to 5 parts by mass, more preferably 0.3 to 3 parts by mass, and even more preferably 0.5 to 1.5 parts by mass, per 100 parts by mass of the rubber component.

(Anti-aging agent)
The rubber composition of the present invention preferably contains an antioxidant.
When the rubber composition contains an antioxidant, the occurrence and progression of cracks in the vulcanized rubber caused by ozone can be suppressed.
Examples of the antioxidant include amine-based antioxidants, hydroquinone-based antioxidants, and phenol-based antioxidants.
Among them, amine-based antiaging agents are preferable. Examples of the amine-based antiaging agents include N-(1,3-dimethyl-butyl)-N'-phenyl-p-phenylenediamine (sometimes called 6PPD) and 2,2,4-trimethyl-1,2-dihydroquinoline polymer.
The antioxidant may be used alone, but it is preferable to use two or more antioxidants in combination.

The content (total content) of the antioxidant in the rubber composition is preferably 0.1 to 5 parts by mass, and more preferably 0.5 to 3 parts by mass, per 100 parts by mass of the rubber component.
The content of the phenol-based antioxidant in the rubber composition of the present invention is preferably 0 to 1 mass %. Examples of the phenol-based antioxidant include 2,2'-methylenebis(4-methyl-6-tert-butylphenol).

The rubber composition of the present invention may contain, in addition to the rubber components, zinc oxide, organic thiosulfate compounds, bismaleimide compounds, stearic acid, vulcanization accelerators, vulcanization retarders, alkylphenol resins, antioxidants, and sulfur described above, compounding agents commonly used in the rubber industry, such as softeners, resins other than alkylphenol resins, waxes, etc., selected appropriately within the scope of the present invention.

(Preparation of Rubber Composition)
The rubber composition of the present invention can be produced by blending the above-mentioned components and kneading them using a kneading machine such as a Banbury mixer, a roll, or an internal mixer.
The amount of each component blended is the same as the amount contained in the rubber composition described above.
The kneading of the components may be carried out in one stage or in two or more stages. For example, when kneading 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 ternary plated metal plated with three different metal species.
The type of metal before plating is not particularly limited, and examples thereof include steel, copper, and the like.
The form of the metal is not particularly limited, and examples thereof include various metal members such as metal cords and metal plates.
Among these, steel cord is preferable.
The steel cord may be either a steel monofilament or a multifilament (twisted cord or a bundle of paralleled cords), and the shape is not limited. When the steel cord is a twisted cord, the twist structure is also not particularly limited, and examples of the twist structure include single twist, multi-twist, layer twist, and composite twist of multi-twist and layer twist.
When the steel cord has a ternary alloy plating layer, the components constituting the alloy plating layer can play a role in enhancing the adhesion between the rubber and the steel cord,
Even when the content of the cobalt compound in the rubber composition described below is small (0.01 part by mass or less per 100 parts by mass of the rubber component), high adhesion can be achieved.

The surface of the metal is subjected to a ternary plating treatment in which three types of metal are plated on it in order to ensure heat-resistant adhesion between the vulcanized rubber and the metal, and further surface treatments such as adhesive treatment may also be performed.
Examples of the metal species for plating include zinc (Zn), copper (Cu), tin (Sn), and cobalt (Co), and it is preferable that the three metal species consist of copper, cobalt, and zinc.
Furthermore, when a copper-zinc-cobalt alloy plating layer is formed, no cobalt compound is used in the rubber composition that coats the steel cord, or the amount of cobalt compound used can be reduced, which can also contribute to improving the crack resistance of the rubber composition.

The ratio (mass ratio) of each element in the copper-zinc-cobalt alloy plating is not particularly limited. For example, from the viewpoint of adhesion to the vulcanized rubber made of the rubber composition of the present invention and corrosion resistance of the plating layer, it is preferable that the copper is 58 to 75 mass% and the cobalt is 0.5 to 10 mass%. At this time, the balance of the alloy plating is zinc and unavoidable impurities. Among them, it is particularly preferable that the ratio of the elements constituting the ternary plating metal is 61 to 70 mass% copper and 1.0 to 5.0 mass% cobalt. At this time, the ratio of the cobalt element present on the outermost metal surface is 1.0 to 5.0 atomic %. By setting the above element ratio, the ratio of the β phase of the Cu-Zn alloy in the plating layer is in an appropriate range, and the workability of the metal surface can be maintained.

When an adhesive treatment is used, an adhesive treatment such as "Chemlock" (registered trademark) manufactured by Lord Corporation can be used.
Furthermore, when the ternary alloy plating layer is a copper-zinc-cobalt alloy plating layer, the plating layer is preferably subjected to a surface treatment to form a cobalt-rich region (a region in which cobalt in the plating layer is aggregated and concentrated). The formation of a cobalt-rich region in the plating layer activates the surface of the plating layer, and the adhesion between the coating rubber composition and the steel cord can be further improved. In this case, the amount of phosphorus present on the outermost surface of the metal, in other words, the amount of phosphorus present in the surface layer region from the surface of the metal to a depth of 5 nm inward, is 3.0 atomic % or less.

The amount of phosphorus (P) in the surface region of the plating can be quantified by using X-ray photoelectron spectroscopy to count the number of atoms present in the plating surface region of the wire excluding carbon, that is, the number of Fe, Cu, Zn, Co, O, P and N atoms, in an analysis area of 20 to 30 μmφ so as not to be affected by the curvature of the steel wire, and to determine the ratio of the number of P atoms to the total number of Cu, Zn, Co, O, P and N atoms being 100.
The atomic number of each atom can be determined by using the photoelectron count numbers of Fe:Fe2p3, O:O1s, P:P2p, Cu:Cu2p3, Zn:Zn2p3, Co:Co2p3, and N:N1s, corrected with the respective sensitivity coefficients.
The number of detected phosphorus atoms [P] can be calculated by the following formula.
[P] = Fp (P2p sensitivity coefficient) x (P2p photoelectron counts per certain time)
The number of detected atoms for other atoms was similarly determined, and the relative atomic percentage of phosphorus was calculated from the results using the following formula: P(%)={[P]/([Fe]+[Cu]+[Zn]+[Co]+[O]+[N]+[P])}×100
It can be found according to:

The method for forming a ternary alloy plating layer on the surface of the steel cord is not particularly limited, and any known method can be used. For example, when forming a copper-zinc-cobalt alloy plating layer, the peripheral surface of the steel wire before wire drawing is repeatedly plated with copper, zinc, and cobalt in this order, copper, cobalt, and zinc in this order, or with an alloy of copper and zinc and cobalt in this order, and then thermally diffused at 450°C to 650°C for 3 to 25 seconds to form a copper-zinc-cobalt alloy plating layer on the surface of the steel wire, thereby obtaining a steel cord having a copper-zinc-cobalt alloy plating layer.

The average thickness of the ternary alloy plating layer is preferably 0.13 to 0.35 μm, more preferably 0.13 to 0.32 μm, and particularly preferably 0.13 to 0.30 μm. If the average thickness of the ternary alloy plating layer is 0.13 μm or more, the area where the iron base is exposed is reduced, improving the initial adhesion, while if it is 0.35 μm or less, excessive adhesion reaction caused by heat during use of the rubber article is suppressed, resulting in stronger adhesion.

Furthermore, the diameter of the steel wire on which the ternary alloy plating layer is formed is preferably 0.60 mm or less, more preferably 0.50 mm or less, and particularly preferably 0.40 mm or less. If the diameter is 0.60 mm or less, the surface strain is small when the rubber article used is repeatedly strained under bending deformation, so that buckling is unlikely to occur. On the other hand, it is preferable that the diameter of the steel wire is 0.10 mm or more from the viewpoints of ensuring the strength of the steel cord and productivity.
Next, the method for producing the vulcanized rubber-metal composite of the present invention will be described.

[Method for producing vulcanized rubber-metal composite]
A ternary plated metal plated with three kinds of metals is coated with the rubber composition of the present invention to obtain a precursor. The precursor rubber composition is then vulcanized to obtain a vulcanized rubber-metal composite in which the metal is coated with vulcanized rubber. The precursor rubber composition may cover at least a portion of the metal, but from the viewpoint of improving the durability of the vulcanized rubber-metal composite, it is preferable to coat the entire surface of the metal.

When a ternary plated steel cord is used as the ternary plated metal, the method of coating the steel cord can be, for example, the method shown below.
In producing the vulcanized rubber-metal composite of the present invention, it is preferable to treat the steel cord with a fatty acid ester oil in order to form the above-mentioned cobalt-rich region before bonding the steel cord to the rubber composition that covers the steel cord. This can further increase the amount of cobalt in the cobalt-rich region, and further improve the adhesion between the vulcanized rubber and the steel cord in the vulcanized rubber-metal composite of the present invention.

Furthermore, in the method for producing a vulcanized rubber-metal composite of the present invention, a surface treatment for forming a cobalt-rich region in the copper-zinc-cobalt alloy plating layer can be performed by intensively working the wire through wire drawing.
For example, the extreme surface of the ternary alloy plating layer of a steel wire plated with copper, zinc, and cobalt in this order can be subjected to a surface treatment in which strong processing is performed by wire drawing using a die using sintered diamond. This strong processing forms a cobalt-rich region on the extreme surface of the ternary alloy plating layer, and activates the extreme surface of the copper-zinc-cobalt alloy plating layer (particularly the very thin surface (within 0.5 to several nm) of the solid surface), further improving the adhesion between the steel cord and the rubber composition. The strong processing can be performed by reducing the lubricity through wire drawing.
For example, when the lubricity is reduced by wire drawing, if the steel wire material comes into contact with the die directly or through an incomplete coating, the extreme surface of the copper-zinc-cobalt alloy plating layer is disturbed, resulting in the crystals being refined and a change in the distribution of cobalt in the plating layer. As a result, it is considered that a cobalt-rich region, which is a region where cobalt is concentrated, is formed on the surface of the copper-zinc-cobalt alloy plating layer.

The wire drawing process in the surface treatment is carried out, for example, as follows.
In order to perform wire drawing in a state where lubricity is reduced to a certain degree by wet wire drawing using a liquid lubricant, the concentration of the lubricating component in the lubricant is lowered below the concentration used in normal wire drawing, or the temperature of the lubricant is lowered below the recommended temperature for use of the lubricant. The degree to which lubricity is reduced during wire drawing depends on the strength and wire diameter of the steel wire to be produced, but for example, when the concentration of the lubricating component is reduced, it is sufficient to set the concentration to 80 to 20% of the concentration of the lubricating component normally used in the wire drawing of steel wire. If the lubricity is reduced too much, it will cause the ternary alloy plating layer to fall off, the quality of the steel wire to deteriorate, or wire breakage and die wear. Conversely, if the lubricity is not reduced enough, the proportion of the cobalt-rich region will decrease, and the adhesion between the rubber and the steel cord will not be sufficiently improved.

In addition, if the heat generation during the wire drawing process is too large, there is a possibility that the lattice defect density of the ternary alloy plating layer will decrease due to the temperature rise, and there is a possibility that the ductility of the steel wire will deteriorate. Therefore, it is preferable to set wire drawing conditions that reduce heat generation, such as those in the following (i) to (v), and to set the wire drawing temperature from the die to 150° C. or less when measured with a contact thermometer.
(i) Set the area reduction rate per die low.
(ii) Set the wire drawing speed to a low level.
(iii) Cool the die to prevent temperature rise.
(iv) Cooling the steel wire entering the die and/or the steel filament exiting the die.
(v) In a continuous wire drawing process using a plurality of dies, the friction coefficient of at least one of the three dies located at the most downstream side is set to 0.18 or more.

When forming a cobalt-rich region, it is better to make the copper-zinc-cobalt alloy plating layer thicker.
Furthermore, in the case of producing the wire by wet continuous wiredrawing, by performing the wiredrawing in the finishing die or in several dies downstream of the wiredrawing including the finishing die under a condition of reduced lubrication as described above and performing the wiredrawing in the other dies under good lubrication conditions, it is possible to reliably produce a copper-zinc-cobalt alloy plating layer which is crystalline inside and has a cobalt-rich region formed on the surface.

As a method for coating the steel cord with the rubber composition of the present invention, for example, the following method can be used.
A predetermined number of ternary plated steel cords are arranged in parallel at a predetermined interval, and the steel cords are covered from above and below with unvulcanized rubber sheets of the rubber composition of the present invention having a thickness of about 0.5 mm to obtain a precursor. The obtained precursor (unvulcanized rubber-metal composite) is vulcanized at a temperature of about 145° C. for about 40 minutes.

The vulcanized rubber-metal composite of the present invention, which has excellent oxygen-resistant and heat-resistant adhesion, is suitable for use as a reinforcing material in rubber articles that require particular strength, such as various automobile tires, conveyor belts, crawlers, and hoses. In particular, it is suitable for use as a reinforcing member for belts, carcass plies, wire chafers, and the like, of various automobile radial tires.

<Tires>
The tire of the present invention comprises the vulcanized rubber-metal composite of the present invention.
The tire of the present invention is excellent in durability since it contains the vulcanized rubber-metal composite of the present invention.
The method for producing the tire of the present invention is not particularly limited as long as it is a method capable of producing the tire so that the vulcanized rubber-metal composite of the present invention is contained within the tire.
In general, a rubber composition containing various components is processed into each component in the unvulcanized stage, and is attached and molded in a tire molding machine by a normal method to form a raw tire. This raw tire is heated and pressurized in a vulcanizer to manufacture a tire. For example, the rubber composition of the present invention is kneaded, and then a ternary plated steel cord is rubber-coated with the obtained rubber composition, and an unvulcanized belt layer, an unvulcanized carcass, and other unvulcanized components are laminated, and the unvulcanized laminate is vulcanized to obtain a tire.
The gas to be filled into the tire may be normal air, air with an adjusted oxygen partial pressure, or an inert gas such as nitrogen, argon, or helium.

<Conveyor belts, crawlers, hoses>
The conveyor belts, crawlers, and hoses of the present invention comprise the vulcanized rubber-metal composites of the present invention.
A processed product containing the vulcanized rubber-metal composite of the present invention is excellent in durability because it contains the vulcanized rubber-metal composite of the present invention which has excellent oxygen-resistant adhesion and heat-resistant adhesion.
Examples of processed products include manufactured rubber articles other than tires, including vulcanized rubber-metal composites, and specific examples include rubber articles that require strength, such as conveyor belts, crawlers, and hoses.

<Examples 1 and 2, Comparative Examples 1 to 9>
[Preparation of Rubber Composition]
Each component was kneaded to prepare a rubber composition according to the compounding composition shown in Table 1. In Table 1, blank spaces indicate that the numerical value is 0. Details of the components shown in Table 1 are as follows.

NR: Natural rubber, RSS#3
CB: HAF grade carbon black Alkylphenol resin: Alkylphenol formaldehyde resin, manufactured by SUMITOMO BAKELITE EUROPE, product name "DUREZ 19900"
Vulcanization accelerator: sulfenamide-based vulcanization accelerator, product name "Noccela CZ" manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
HTS: Hexamethylene bisthiosulfate disodium salt dihydrate BMI: N,N'-(4,4-diphenyl-methane)bismaleimide, manufactured by Daiwa Kasei Kogyo Co., Ltd., product name "BMI-1000"
Zinc oxide: manufactured by Hakusui Tech Co., Ltd., zinc oxide, BET specific surface area = 4.2 ^m2 /g
Activated zinc oxide: Activated zinc oxide manufactured by Seido Chemical Industry Co., Ltd., BET specific surface area = 63.0 ^m2 /g
Sulfur: Insoluble sulfur (20% by mass oil treated product)

[Preparation of vulcanized rubber-metal composite]
In Comparative Examples 1 to 9, a brass-plated steel cord (comparative steel cord) was used, and in Examples 1 and 2, a ternary-plated steel cord (ternary-plated steel cord) plated with three kinds of metals was used.
The steel cord for the comparative example was a brass-plated steel cord (1+6×0.34 mm (strand diameter)) (Cu: 63 mass %, Zn: 37 mass %).

(Production of ternary plated steel cord)
A steel filament with a diameter of 1.7 mm was repeatedly plated with Cu, Zn, and Co in this order so that the Cu content in the plating was 67.0 mass%, the Zn content was 29.0 mass%, and the Co content was 4.0 mass%. Then, a thermal diffusion treatment was performed at 550°C for 5 seconds to obtain a steel filament with a ternary alloy plating. Then, only the extreme surface of the ternary alloy plating layer was subjected to strong processing (surface treatment) by wire drawing using a diamond die. In this way, a steel filament with a diameter of 0.225 mm and an average plating thickness of 0.25 μm was obtained. Using the obtained steel filament, a steel cord was produced as a twisted cord with a structure of 1+6×0.34 mm (strand diameter). The amount of phosphorus present in the surface layer region from the surface of the steel cord to a depth of 5 nm inward is 0.62 atomic % as a percentage of the total amount excluding the amount of carbon.

(Preparation of unvulcanized rubber-metal composite)
The obtained brass-plated steel cords or ternary-plated steel cords were arranged in parallel at intervals of 12.5 mm and covered with the prepared rubber composition to produce an unvulcanized rubber-metal composite (unvulcanized steel cord topping piece) having a thickness of 5 mm.

(Vulcanization)
The unvulcanized rubber-metal composite was vulcanized at 145° C. for 40 minutes to prepare a vulcanized rubber-metal composite.

<Evaluation>
1. Oxygen resistance (4 days)
The vulcanized rubber-metal composite immediately after vulcanization was heated at 120° C. for 4 days in an oxygen atmosphere. Thereafter, the steel cord was pulled out from the vulcanized rubber-metal composite in accordance with ASTM D 2229. The coverage of the vulcanized rubber adhering to the steel cord was determined by visual observation as 0 to 100 area %. The coverage of each Example and Comparative Example was indexed, with the coverage of Comparative Example 3 being set to 100. The results are shown in Table 1. The acceptable range is 170 or more.

2. Heat-resistant adhesion (7 days)
The vulcanized rubber-metal composite immediately after vulcanization was heated at 120° C. for 7 days in a nitrogen atmosphere. After that, the steel cord was pulled out from the vulcanized rubber-metal composite in accordance with ASTM D 2229. The coverage of the vulcanized rubber attached to the cord was determined by visual observation as 0 to 100% by area. The coverage of Comparative Example 3 was set as 100, and the coverage of each Example and Comparative Example was indexed. The results are shown in Table 1. The acceptable range is 104 or more.

3. EB (durability)
The durability of the vulcanized rubber used in the vulcanized rubber-metal composite was evaluated by elongation at break (EB).
The rubber compositions of the examples and comparative examples were vulcanized to prepare vulcanized rubber test pieces having a thickness of 2 mm. The test pieces were pulled at a speed of 100 mm/min at 25° C., and the strain at which the test pieces broke was measured. The length was measured. The length at break was calculated as the length relative to the length (100%) before the test piece was pulled. The breaking elongation of Comparative Example 3 was set to 100, and the breaking elongation of each of the Examples and Comparative Examples was calculated. The breaking elongation was indexed, and the results are shown in Table 1. The acceptable range is 92 or more.

As can be seen from Table 1, the vulcanized rubber-metal composites of Examples 1 and 2 have a high coverage of vulcanized rubber on the steel cords pulled out of the vulcanized rubber-metal composites, both after heating at 120°C in an oxygen atmosphere for four days and after heating at 120°C in a nitrogen atmosphere for seven days. Therefore, it can be seen that the vulcanized rubber-metal composites of Examples 1 and 2 have both excellent oxygen-resistant adhesion and excellent heat-resistant adhesion. Therefore, it can be seen that the vulcanized rubber-metal composites of Examples 1 and 2 have superior durability compared to Comparative Examples 1 to 9.

The vulcanized rubber-metal composite of the present invention has excellent oxygen-resistant and heat-resistant adhesive properties, and is therefore suitable for use as a reinforcing material in rubber articles that require particular strength, such as various automobile tires, conveyor belts, crawlers, and hoses. In particular, it is suitable for use as a reinforcing member for belts, carcass plies, wire chafers, and the like, of various automobile radial tires.

Claims (11)

A vulcanized rubber-metal composite comprising vulcanized rubber and a metal, the vulcanized rubber and the metal being bonded to each other ,
The vulcanized rubber is
A rubber component,
zinc oxide having a nitrogen adsorption specific surface area of 40 to 100 m ² /g, in an amount of 2 parts by mass or more per 100 parts by mass of the rubber component;
0.6 parts by mass or more and 2.0 parts by mass or less of stearic acid per 100 parts by mass of the rubber component;
an organic thiosulfate compound ;
a vulcanized rubber of a rubber composition having a cobalt-containing compound content of 0.1 parts by mass or less per 100 parts by mass of the rubber component,
The metal is a ternary plating metal plated with three kinds of metal species,
the three metal species being copper, cobalt, and zinc;
A vulcanized rubber-metal composite, wherein the amount of phosphorus element present in a surface layer region from the surface of the metal to a depth of 5 nm in an inward direction is 3.0 atomic % or less,
The zinc oxide is composed of zinc oxide having a nitrogen adsorption specific surface area of 40 to 100 m ² /g, or is composed of zinc oxide having a nitrogen adsorption specific surface area of 40 to 100 m ² /g and zinc oxide having a nitrogen adsorption specific surface area of 1.0 to 10 m ² /g, and the total amount c of zinc oxide in the rubber composition, which is the amount of zinc oxide contained in either of these configurations, and the content d of stearic acid, satisfies the relationship of [c/(c+d)]×100=75 or more and less than 100, on a mass basis . The vulcanized rubber-metal composite according to claim 1, wherein the content of the organic thiosulfate compound in the rubber composition is 0.1 parts by mass or more and less than 2.0 parts by mass per 100 parts by mass of the rubber component. The vulcanized rubber-metal composite according to claim 1 or 2, wherein the rubber composition further contains 0.1 to 2.0 parts by mass of a bismaleimide compound per 100 parts by mass of the rubber component. The rubber composition contains, as the zinc oxide,
The vulcanized rubber-metal composite according to any one of claims 1 to 3, comprising zinc oxide having a nitrogen adsorption specific surface area of 40 to 100 m ² /g and zinc oxide having a nitrogen adsorption specific surface area of 1.0 to 10 m ² /g , and the total content of the zinc oxide is 7.6 parts by mass or more per 100 parts by mass of the rubber component. 5. The vulcanized rubber-metal composite according to claim 1, wherein the rubber composition contains, as the zinc oxide, zinc oxide having a nitrogen adsorption specific surface area of 40 to 100 m ² /g and zinc oxide having a nitrogen adsorption specific surface area of 1.0 to 10 m ² /g, and the content a of the zinc oxide having a nitrogen adsorption specific surface area of 40 to 100 m ² /g in the rubber composition and the content b of the zinc oxide having a nitrogen adsorption specific surface area of 1.0 to 10 m ² /g in the rubber composition satisfy the relationship, on a mass basis, of [a/(a+b)]×100=20 or more and less than 100. The vulcanized rubber-metal composite according to any one of claims 1 to 5 , wherein the ratio of elements constituting the ternary plating metal is 61 to 70 mass % for copper and 1.0 to 5.0 mass % for cobalt. 7. The vulcanized rubber-metal composite according to claim 1, wherein the organic thiosulfate compound is hexamethylene bisthiosulfate disodium salt dihydrate. A tire comprising the vulcanized rubber-metal composite of any one of claims 1 to 7 . A hose comprising the vulcanized rubber-metal composite according to any one of claims 1 to 7 . A crawler comprising the vulcanized rubber-metal composite according to any one of claims 1 to 7 . A conveyor belt comprising the vulcanized rubber-metal composite according to any one of claims 1 to 7 .