JP2011168713A - Rubber-steel composite - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber-steel composite which improves the processability and heat deterioration resistance of a rubber composition, inhibits blooming seen at the time of blending resorcinol or RF resin as low as possible, and highly satisfies both initial adhesion and wet heat-resistant adhesion. <P>SOLUTION: The rubber-steel composite contains a rubber composition and a steel wire or steel cord obtained by twisting a plurality of such steel wires together. The rubber composition contains (A) a rubber component, (B) sulfur and (C) a specific thiazole compound. The steel wire has a brass plating layer on its peripheral surface and the concentration of a transition metal other than zinc and copper in a surface of the brass plating layer is ≥0.01 mass%. A tire including the rubber-steel composite is also provided. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a rubber-steel composite comprising a rubber composition containing a specific thiazole compound and a specific steel wire or steel cord.

Conventionally, in rubber articles such as automobile tires, conveyor belts, and hoses that require particularly high strength, brass plating is used as a metal reinforcing material with a rubber composition for the purpose of reinforcing the rubber and improving the strength and durability. A coated composite material is used.
In order for this rubber-brass-plated steel cord composite material to exhibit a high reinforcing effect and to obtain reliability, stable adhesion with little change with time is required between the rubber-brass-plated steel cord, and particularly in direct vulcanization adhesion. Various studies have been made to improve the adhesion between the rubber composition and the brass-plated steel cord, in particular, the wet heat resistance.

  For example, Patent Document 1 reports an adhesive made of a mixed polyester having a resorcin skeleton having a weight average molecular weight of 3000 to 45000. However, mixed polyester having a large molecular weight is not satisfactory although compatibility with rubber is improved compared to resorcin-formaldehyde resin (hereinafter abbreviated as “RF resin”). When blended with rubber, there is a problem that the viscosity of the rubber composition is increased and processability is lowered, and the heat-and-moisture resistance is not satisfactory.

On the other hand, Patent Document 2 reports a rubber composition in which resorcin, or an RF resin obtained by condensing resorcin and formalin is blended for the purpose of improving wet heat-resistant adhesion. By blending the RF resin, the wet heat resistance between the rubber composition and the steel cord is improved.
However, resorcinol and RF resin have very high polarity, so they are poorly compatible with rubber. Depending on processing conditions such as mixing of rubber compositions, heating during rubber composition processing, conditions during storage of rubber compositions, etc. Since so-called blooms in which resorcin and RF resin are deposited are generated, the change over time of the rubber composition is large, and it is difficult to stably develop adhesiveness.

By the way, as performance required in adhesion | attachment with a rubber composition and a brass plating steel cord, not only the above-mentioned wet heat adhesiveness but initial adhesiveness, for example, adhesiveness after a short time vulcanization, is also requested | required. .
In order to improve this initial adhesiveness and heat resistant adhesiveness, Patent Document 3 contains 0.1 to 5 parts by weight of a maleimide resin and 0.5 to 8 parts by weight of a bisphenol compound having two tert-butyl groups, and A rubber-steel composite composed of a rubber composition containing at least one higher fatty acid and a steel cord having a specific brass plating layer has been proposed.
Patent Document 4 proposes improving the adhesion between a rubber composition and a brass-plated steel wire by improving the brass plating of the steel wire.
However, it is difficult to achieve both initial adhesiveness and wet heat resistant adhesiveness, and further improvements from both the rubber composition and brass-plated steel cord are required.

JP-A-7-118621 JP 2001-234140 A JP 2004-82878 A JP 2009-91691 A

  The present invention has been made under such circumstances, and improves the processability and heat deterioration resistance of the rubber composition, suppresses the bloom seen when compounding resorcinol and RF resin as much as possible, and has initial adhesiveness. It is an object of the present invention to provide a rubber-steel composite in which wet heat adhesiveness is highly compatible.

（式中、Ｒ¹〜Ｒ⁴は、それぞれ独立に水素原子、炭素数１〜１０の直鎖アルキル基、炭素数３〜１２の分岐アルキル基、炭素数１〜１０の直鎖アルコキシ基及び炭素数３〜１２の分岐アルコキシ基から選ばれる基である。Ｒ⁵は、炭素数１〜１０の直鎖アルキル基、炭素数３〜１２の分岐アルキル基、脂環式炭化水素基及び芳香族炭化水素基から選ばれる基である。ｎは、２〜４の整数である。） As a result of intensive studies to solve the above problems, the present inventor has obtained a rubber composition containing a rubber component and a thiazole compound having a specific structure, and a steel wire having a specific brass plating layer or the steel wire. It has been found that the problem can be solved by a rubber-steel composite comprising a steel cord formed by twisting a plurality of steel cords. The present invention has been completed based on such findings.
That is, the present invention is a rubber-steel composite comprising a rubber composition and a steel cord formed by twisting a plurality of steel wires or steel wires, and the rubber composition comprises (A) a rubber component. (B) Sulfur and (C) a thiazole compound represented by the following general formula (1), wherein the steel wire has a brass plating layer on its peripheral surface, and the surface of the brass plating layer The rubber-steel composite and the tire comprising the rubber-steel composite are characterized in that the concentration of transition metal excluding zinc and copper is 0.01% by mass or more.

(In the formula, R ^{1 to} R ⁴ are each independently a hydrogen atom, a linear alkyl group having 1 to 10 carbon atoms, a branched alkyl group having 3 to 12 carbon atoms, a linear alkoxy group having 1 to 10 carbon atoms, and carbon. R ⁵ is a group selected from a branched alkoxy group having 3 to 12. R ⁵ is a linear alkyl group having 1 to 10 carbon atoms, a branched alkyl group having 3 to 12 carbon atoms, an alicyclic hydrocarbon group, and an aromatic carbon group. (It is a group selected from a hydrogen group. N is an integer of 2 to 4.)

  According to the present invention, the processability and heat resistance of the rubber composition are improved, the bloom seen when blending resorcinol and RF resin is suppressed as much as possible, and both initial adhesiveness and wet heat adhesiveness are more highly compatible. A rubber-steel composite can be provided. In particular, by blending the thiazole compound represented by the general formula (1) into the rubber composition, the vulcanization start time of the rubber composition is delayed, and the adhesion reaction proceeds preferentially. The above-mentioned brass plating of the wire and a strong adhesive layer are formed, and the adhesiveness between the rubber composition and the steel cord, which is stable from vulcanization for a short time to after the wet heat deterioration, is developed.

  The rubber-steel composite of the present invention is a rubber-steel composite comprising a rubber composition and a steel cord formed by twisting a steel wire or a plurality of the steel wires, and the rubber composition is (A A rubber component, (B) sulfur, and (C) a thiazole compound represented by the following general formula (1), wherein the steel wire has a brass plating layer on its peripheral surface, and the brass plating The concentration of the transition metal excluding zinc and copper on the surface of the layer is 0.01% by mass or more.

式中、Ｒ¹〜Ｒ⁴は、それぞれ独立に水素原子、炭素数１〜１０の直鎖アルキル基、炭素数１〜１０の直鎖アルコキシ基、炭素数３〜１２の分岐アルキル基及び炭素数３〜１２の分岐アルコキシ基から選ばれる基である。Ｒ⁵は、炭素数１〜１０の直鎖アルキル基、炭素数３〜１２の分岐アルキル基、脂環式炭化水素基及び芳香族炭化水素基から選ばれる基である。ｎは、２〜４の整数である。 [Thiazole compound]

In the formula, R ^{1 to} R ⁴ are each independently a hydrogen atom, a linear alkyl group having 1 to 10 carbon atoms, a linear alkoxy group having 1 to 10 carbon atoms, a branched alkyl group having 3 to 12 carbon atoms, and a carbon number. It is a group selected from 3 to 12 branched alkoxy groups. R ⁵ is a group selected from a linear alkyl group having 1 to 10 carbon atoms, a branched alkyl group having 3 to 12 carbon atoms, an alicyclic hydrocarbon group, and an aromatic hydrocarbon group. n is an integer of 2-4.

In Formula (1), if having a substituent at any position of R ¹ to R ^4, the synthesis and manufacture of chemicals, it is preferable to have a substituent at the position of R ^1. Especially, when R < ¹ > and R < ³ > is an alkyl group or an alkoxy group, it is preferable that it is a C1-C4 linear alkyl group or a linear alkoxy group.
Moreover, when any of R ^{1 to} R ⁴ is an alkyl group or an alkoxy group, the number of carbon atoms is preferably 1. Furthermore, it is particularly preferable that R ^{1 to} R ⁴ are all hydrogen atoms from the viewpoint of improving adhesiveness. In any case, it is because the ease of synthesis of the thiazole compound as the component (C) and the adhesion between the rubber composition and the steel cord are improved.

Specific examples of the linear alkyl group having 1 to 10 carbon atoms and the branched alkyl group having 3 to 12 carbon atoms represented by R ^{1 to} R ⁴ in the general formula (1) include, for example, a methyl group, an ethyl group, and an n-propyl group. Alkyl groups such as isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, various pentyl groups, various hexyl groups, various octyl groups, various nonyl groups, various decyl groups, etc. Specific examples of the C-10 linear alkoxy group and the C3-C12 branched alkoxy group include, for example, a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, an isobutoxy group, and a sec-butoxy group. And various alkoxy groups such as a tert-butoxy group. In addition, various alkyl groups refer to alkyl groups including all isomers at the same carbon number, and various alkoxy groups are the same. The same applies to other similar terms.

The thiazole compound used as the component (C) according to the present invention is the general formula (1), wherein R ⁵ is a linear alkyl group having 1 to 10 carbon atoms, a branched alkyl group having 3 to 12 carbon atoms, or an alicyclic ring. It is a group selected from the formula hydrocarbon group and aromatic hydrocarbon group.
Examples of the linear alkyl group having 1 to 10 carbon atoms and the branched alkyl group having 3 to 12 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, and a sec-butyl group. Preferred examples include various alkyl groups such as a group, tert-butyl group, various pentyl groups, various hexyl groups, various octyl groups, various nonyl groups, and various decyl groups.
Further, the alicyclic hydrocarbon group is preferably a cycloalkyl group, for example, a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cyclooctyl group, a cyclodecyl group, a cyclododecyl group, a decalinyl group, an adamantyl group, etc. Can be mentioned. Note that these cycloalkyl groups preferably have a carbon number of 3 to 18 and may have one or more alkyl groups on the cyclo ring.
Preferred examples of the aromatic hydrocarbon group include an aryl group and an aralkyl group. Examples of the aryl group include a phenyl group, a naphthyl group, and an anthryl group. Examples of the aralkyl group include a benzyl group, a phenethyl group, a 3-phenylpropyl group, various naphthylmethyl groups, various naphthylethyl groups, and various naphthylpropyl groups. Preferred examples include a group. The aryl group preferably has 6 to 18 carbon atoms, and the aralkyl group preferably has 7 to 18 carbon atoms, and may have one or more alkyl groups on the aromatic ring. good.
R ⁵ is preferably a group selected from a cycloalkyl group and an aralkyl group among the groups described above, more preferably a cyclohexyl group or a benzyl group, and particularly preferably a cyclohexyl group.

  The reason why n in the general formula (1) needs to be an integer of 2 to 4 is that if it is outside this range, the effect of improving adhesiveness is lowered. From this viewpoint, n is preferably an integer of 2 or 3, and n is particularly preferably an integer of 2.

Specific examples of the thiazole compound (C) include 2- (cyclopentyldithio) benzothiazole, 2- (cyclohexyldithio) benzothiazole, 2- (cyclooctyldithio) benzothiazole, 2- (cyclododecyldithio) benzothiazole. 2- (benzyldithio) benzothiazole, 2- (phenethyldithio) benzothiazole, 2- (tert-butyldithio) benzothiazole, 2- (2-ethylhexyldithio) benzothiazole, and the like.
Of these, 2- (cyclohexyldithio) benzothiazole represented by the following chemical formula (2) and 2- (benzyldithio) benzothiazole represented by the following chemical formula (3) are particularly preferable from the viewpoints of performance and manufacturability. It is. The (C) component thiazole compound may be used alone or in combination of two or more.

The thiazole compound of the component (C) having the structure represented by the general formula (1) does not cause deterioration in physical properties of the vulcanized rubber and hardly causes blooming. Therefore, the rubber composition according to the present invention has a steel cord Excellent adhesion.
The thiazole compound as the component (C) having the structure represented by the general formula (1) can be synthesized, for example, by the method described in US Pat. No. 3,859,297.

  The rubber composition according to the present invention preferably includes (C) 0.1 to 5 parts by mass of the thiazole compound represented by the general formula (1) with respect to 100 parts by mass of the rubber component. If this content is 0.1 parts by mass or more, adhesion between the rubber composition and the steel cord is preferably improved, while if it is 5 parts by mass or less, blooming can be preferably suppressed. From these viewpoints, the more preferable content is in the range of 0.4 to 5 parts by mass.

[Rubber component]
In the rubber composition according to the present invention, the rubber component used as the component (A) is not particularly limited as long as it is capable of sulfur crosslinking, i.e., has a double bond in the main chain. From the viewpoint of obtaining a composition in which the function of the thiazole compound as the component (C) is sufficiently exerted and capable of expressing a stable and high adhesion to metal, at least one of natural rubber and synthetic polyisoprene rubber is used. The rubber component is preferably composed of 50% by weight or more natural rubber and 50% by weight or less synthetic rubber, more preferably 70% by weight or more natural rubber and 30% by weight or less synthetic rubber. Particularly preferred is a rubber component consisting only of natural rubber.
Examples of the synthetic rubber include synthetic polyisoprene rubber, polybutadiene rubber, styrene-butadiene copolymer, ethylene-propylene-diene copolymer, chloroprene rubber, halogenated butyl rubber, and acrylonitrile-butadiene rubber. These synthetic rubbers may be used alone or in combination of two or more.

[sulfur]
In the rubber composition according to the present invention, the sulfur of the component (B) used for the vulcanization of the rubber component (A) described above is not particularly limited, and conventionally, for sulfur crosslinking of rubber having a double bond in the main chain. Arbitrary ones can be appropriately selected from those used. Examples of the sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, surface-treated sulfur, insoluble sulfur and the like.
In the rubber composition according to the present invention, the sulfur content is preferably in the range of 0.3 to 10 parts by mass with respect to 100 parts by mass of the rubber component (A). If this content is 0.3 parts by mass or more, vulcanization proceeds preferably, and the adhesive strength between the metal and the vulcanized rubber is preferably ensured. On the other hand, when the amount is 10 parts by mass or less, the aging resistance of the vulcanized rubber is hardly lowered, and the adhesive strength with a steel cord, particularly a steel cord to which brass plating is applied, is ensured. The sulfur content is more preferably in the range of 0.3 to 8 parts by mass, particularly preferably in the range of 0.5 to 8 parts by mass.

[Cobalt compound]
The rubber composition according to the present invention preferably contains no cobalt compound from the viewpoint of improving the heat deterioration resistance and crack growth resistance of the rubber composition.
As this cobalt compound, cobalt salts of organic acids such as cobalt naphthenate, cobalt stearate, cobalt neodecanoate, cobalt rosinate, cobalt versatate, cobalt tall oil, cobalt oleate, cobalt linoleate, cobalt linolenate, Examples thereof include a composite salt obtained by replacing a part of an organic acid of a cobalt salt of these organic acids with boric acid, and a cobalt metal complex such as cobalt acetylacetonate.

[Other ingredients]
In the rubber composition according to the present invention, together with the components (A) to (C), compounding agents usually used in the rubber industry, for example, fillers such as carbon black and silica, and vulcanization other than the component (C) Accelerators, vulcanization retarders, process oils, zinc white, stearic acid, anti-aging agents, and the like can be included as long as the effects of the present invention are not impaired.
Among these, fillers such as carbon black and silica are known as reinforcing materials for increasing the tensile strength, breaking strength, modulus, hardness, etc. of vulcanized rubber, and improving wear resistance and tensile resistance. Zinc white is known as a vulcanization acceleration aid that forms a complex compound with a fatty acid and enhances the vulcanization acceleration effect.
Examples of the antioxidant include 3C (N-isopropyl-N′-phenyl-p-phenylenediamine, 6C [N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine], AW (6 -Ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline), high-temperature condensates of diphenylamine and acetone, and the like.

[Preparation of rubber composition]
The rubber composition according to the present invention may be mixed with a Banbury mixer, a roll, an internal mixer or the like by adding at least one of the above-mentioned compounding agents, if desired, together with the components (A), (B) and (C) described above. It can be prepared by kneading using a kneader.

[Steel wire]
The steel wire according to the present invention is used in a rubber-steel composite as a single wire of a steel wire or as a steel cord formed by twisting a plurality of steel wires.
The twist structure of the steel cord is not particularly limited, and examples thereof include a twist structure such as a single twist, a double twist, a layer twist, and a compound twist of a double twist and a layer twist.

The steel wire according to the present invention has a brass plating layer on its peripheral surface, and the concentration of the transition metal excluding zinc and copper on the surface of the brass plating layer is 0.01% by mass or more. To do. If the concentration of the transition metal excluding zinc and copper is 0.01% by mass or more, the initial adhesiveness can be sufficiently obtained even for a rubber composition from which an adhesion promoter such as a cobalt compound has been removed. By removing the adhesion promoter from the object, it becomes possible to enjoy improved toughness and crack growth resistance after thermal degradation.
Here, brass is also called brass or brass and is an alloy made of copper (Cu) and zinc (Zn). And the surface of a brass plating layer refers to the surface layer area | region of a brass plating layer to the depth of 10 nm inside a wire radial direction.
The transition metal is from the fourth period scandium (Sc) to zinc (Zn), the fifth period yttrium (Y) to cadmium (Cd), the sixth period lutetium (Lu). It refers to metal elements up to mercury (Hg). The transition metal is preferably cobalt (Co) from the viewpoint of improving adhesiveness.

  The steel wire according to the present invention preferably further has a phosphorus concentration of 2.5% by mass or less and a zinc concentration of 15% by mass or less on the surface of the brass plating layer. This is because if the phosphorus concentration on the surface of the plating layer is 2.5 mass% or less, the adhesion inhibition effect due to phosphorus can be suppressed. Similarly, when the zinc concentration is 15% by mass or less, the formation of the ZnO layer on the surface of the plating layer can be suppressed, and the adhesion inhibition effect due to the ZnO layer can be suppressed. By reducing these phosphorus concentration and zinc concentration, suitable adhesive performance can be obtained even if the cobalt compound is removed from the rubber composition.

[Quantification method of transition metal content and phosphorus content]
Phosphorus quantification in the surface layer region of the brass plating layer is carried out by using X-ray photoelectron spectroscopy to analyze atoms present in the wire surface region of the plating layer in an analysis area of 20 to 30 μmφ so as not to be affected by the curvature of the wire. The content was determined by measuring. The number of atoms of each atom is C: C _1S , O: O _1S , P: P _2P , Cu: Cu _{2p3 / 2} , Zn: Zn _{2p3 / 2} , N: N _1S and transition metal (for example, Co: Co _{2p3 / 2} ) Using the respective photoelectron counts, correction was made with each sensitivity coefficient.
Further, the distribution of elements in the depth direction from the peripheral surface to the inside in the wire radial direction can be measured in detail by performing argon etching or the like.
In addition, if the surface of the wire before analysis is covered with oil or contaminated with organic matter, the wire surface is washed with an appropriate solvent for accurate analysis, and if necessary, Therefore, it is necessary to perform a light dry cleaning that does not modify the surface.

  It is preferable that the ratio of copper to the total amount of copper and zinc in the entire brass plating layer of the steel wire according to the present invention is 60 to 70% by mass. If the ratio of copper to the total amount of copper and zinc in the entire plating layer is 60% by weight or more, the wire drawing property can be improved, and the inhibition of productivity due to disconnection can be suitably prevented, and the mass productivity of the steel cord is improved.

  It is preferable that the average thickness of the brass plating layer of the steel wire according to the present invention is 0.13 to 0.30 μm. If the average thickness of a brass plating layer is 0.13 micrometer or more, it can prevent suitably that the part which an iron ground exposes increases and initial adhesiveness is inhibited. On the other hand, if it is 0.30 micrometer or less, it can prevent suitably that adhesion reaction will advance excessively with the heat | fever while using rubber articles, and it will become weak adhesive.

  The diameter of the steel wire according to the present invention is advantageously 0.40 mm or less. When the diameter is 0.40 mm or less, it is possible to suppress the occurrence of buckling by suppressing an increase in surface strain when the used rubber article is repeatedly strained under bending deformation. Further, if the diameter of the steel wire is less than 0.10 mm, the number of steel wires in the case of constituting the steel cord is excessive and not economical, and therefore the diameter of the steel wire is further 0.10 to 0.40 mm. preferable.

[Method of manufacturing steel wire]
The steel wire according to the present invention is generally manufactured by, for example, drawing a wire having a diameter of about 5 mm subjected to brass plating. In this manufacturing process, a lubricant is naturally used, but in particular, in the final wire drawing step, thinning is performed using a die having about 20 passes disposed in the liquid lubricant. In this final wire drawing process, an extreme pressure is generated between the cord and the die, and the temperature becomes very high. Therefore, lubrication based on phosphoric acid is necessary to ensure lubricity at extreme pressures and high temperatures. It is customary to use agents.

This lubricant reacts with the wire surface during wire drawing to form a lubricant film layer, that is, a phosphate compound layer, which eases input under extreme pressure and high temperature conditions and realizes mass production of wires. . Therefore, it is inevitable that phosphoric acid is incorporated during the plating of the wire in the manufacturing process. When this phosphoric acid compound layer is on the plating surface, copper in the brass plating diffuses to the rubber side, forming CuxS and hindering an adhesion reaction in which adhesion is performed.
Also, when brass plating, which is an alloy of copper (Cu) and zinc (Zn), is applied, the surface is oxidized over time to produce ZnO. This ZnO layer is also bonded to the adhesive compound layer in the same manner as the phosphate compound layer. It will inhibit the reaction.

  Therefore, removing the phosphate compound layer and the ZnO layer from the plating surface before bonding with the rubber is effective in improving the adhesion with the rubber. For this purpose, it is important to remove the phosphate compound layer and the ZnO layer on the surface of the steel wire after drawing, but cleaning with an acidic or alkaline aqueous solution is environmentally undesirable. When considering the manufacturing process, safety may be an issue.

A method for producing a steel wire suitably used for the rubber-steel composite of the present invention includes a brass plating process for forming a brass plating layer on the peripheral surface of the steel wire, and a wire drawing of the steel wire on which the brass plating layer is formed. It comprises a wire drawing step and a washing step of washing the surface of the drawn steel wire with an aqueous solution containing a transition metal compound. That is, it is characterized in that a cleaning process for cleaning with an aqueous solution containing a transition metal compound is provided instead of the above-described cleaning process with an acidic or alkaline aqueous solution. A brass plating process and a wire drawing process are performed by a normal well-known method.
By washing the surface of the drawn steel wire with an aqueous solution containing a transition metal compound, the phosphate compound layer or ZnO layer that inhibits the adhesion reaction with the rubber described above can be dissolved.

  Here, the transition metal is as described above, and cobalt is preferable from the viewpoint of improving adhesiveness. The cobalt compound contained in the aqueous solution for the washing step is preferably a compound selected from cobalt chloride, cobalt nitrate, cobalt sulfate, cobalt acetate, cobalt citrate, cobalt gluconate and cobalt acetylacetonate. In addition, as the transition metal compound contained in the aqueous solution, nitric acid, sulfuric acid or acetate containing Fe and Ag can be used.

In the cleaning step according to the present invention, the pH of the aqueous solution is preferably about 5 to 8. This is because if the pH of the aqueous solution is within this range, the adhesion to the rubber composition can be improved without adversely affecting the plating. If the pH is in a neutral range of about 5 to 8, the load on the environment is reduced, and safety against exposure to the user and reagent safety during production can be ensured.
The cleaning conditions in the cleaning step according to the present invention may be set as appropriate according to the concentration of the aqueous solution. For example, in the case of an aqueous solution containing cobalt acetate, the cleaning time is 30 to 60 seconds at a concentration of 10 g / L. Is a preferable condition.

The steel wire that has undergone the cleaning step using the aqueous solution containing the transition metal as a salt described above has no oxide layer such as a ZnO layer or a phosphoric acid compound layer on the surface of the brass plating, and further transition metal compounds excluding zinc and copper When an aqueous solution containing a cobalt compound is preferably used, a transition metal excluding 0.01% by mass or more of zinc and copper, preferably 0.01% by mass or more of cobalt, is present on the plating surface. That is, by passing through the above-described washing step, a plating surface having transition metals other than zinc and copper, preferably cobalt, which functions as an adhesion promoter, in addition to having no adhesion reaction inhibitor with the rubber composition. As a result, the adhesion of the wire to rubber is greatly improved. Therefore, even if the adhesion promoter on the rubber composition side is omitted, the adhesion between the wire and the rubber composition can be ensured. On the other hand, since the adhesion promoter on the rubber composition side can be omitted, the deterioration resistance and crack growth resistance of the rubber can be improved.
On the other hand, the presence of transition metals (for example, cobalt) excluding zinc and copper exceeding 20% by mass on the surface of the brass plating may function as an adhesion inhibiting factor with rubber rather than function as an adhesion promoter. The concentration of transition metal (preferably cobalt) excluding zinc and copper is preferably 20% by mass or less.

[Rubber-steel composite]
The rubber composition according to the present invention and the steel wire or the steel cord obtained as described above are used as a rubber-steel composite, and the rubber formed by coating the steel cord with the rubber composition according to the present invention. -It is particularly preferred to be used as a steel composite.

As a method for coating the steel wire or the steel cord, for example, the following method can be used.
Preferably, a predetermined number of brass-plated steel wires or steel cords are arranged in parallel at predetermined intervals, and the steel wires or steel cords are arranged from the upper and lower sides, and the uncrosslinked rubber having a thickness of about 0.5 mm made of the composition. It is coated with a sheet and vulcanized at a temperature of about 160 ° C. for about 20 minutes. The rubber-steel composite thus obtained has excellent heat resistant adhesiveness.

[Use of rubber-steel composite]
The rubber-steel composite of the present invention is suitably used as a reinforcing material used for rubber articles such as various automobile tires, conveyor belts, hoses and the like that require particularly high strength. In particular, it is suitably used as a reinforcing member for various automobile radial tire belts, carcass plies, wire chafers, and the like.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
In addition, about the rubber composition obtained in each case, various characteristics were calculated | required with the following method.
<Broom resistance>
After storing the unvulcanized rubber composition at 40 ° C. for 7 days, whether or not the compounding agent was deposited on the rubber surface was visually confirmed and evaluated according to the following criteria.
○: No compounding agent is deposited on the surface.
Δ: Precipitation of the compounding agent is observed on a part of the surface.
X: The compounding agent has precipitated on the whole surface.

<Mooney viscosity, Mooney scorch time>
Based on JIS K 6300-1: 2001, Mooney viscosity [ML _{1 + 4} ] (measured at 130 ° C.) and Mooney scorch time (measured at 130 ° C.) were measured. The evaluation was expressed as an index according to the following formula, with the value of Comparative Example 3 being 100. The Mooney viscosity is better as the value is smaller, and the Mooney scorch time is better as the value is larger.
Mooney viscosity index = {(Mooney viscosity of test sample) / (Mooney viscosity of Comparative Example 3)} × 100
Mooney scorch time index = {(Mooney scorch time of test sample) / (Mooney scorch time of Comparative Example 3)} × 100

<Toughness after thermal degradation (TF)>
A vulcanized rubber composition obtained by vulcanization at 160 ° C. for 20 minutes was thermally deteriorated at 100 ° C. for 2 days, and then a JIS dumbbell-shaped No. 3 sample was used in accordance with JIS K 6251: 2004. Tensile tests were conducted at 0 ° C., the elongation at break after thermal degradation (Aged E _b ) and the tensile stress at break after thermal degradation (Aged TS _b ) were measured, and the results were _expressed by the following formulas. The larger the visual value, the better the workability.
Toughness after thermal degradation (TF) = elongation after cutting after thermal degradation (Aged E _b ) × tensile stress after cutting after thermal degradation (Aged TS _b )
Toughness (TF) index after thermal degradation = {(Toughness after thermal degradation of test sample) / (Toughness after thermal degradation of Comparative Example 3)} × 100

<Crack growth resistance>
A constant stress fatigue test was performed using a Uejima fatigue tester, the number of times until fracture occurred, and the index was evaluated by the following formula.
Crack growth resistance index = {(number of test samples) / (number of comparative example 3)} × 100

<Initial adhesion and wet heat resistance>
Brass-plated steel cords are arranged in parallel at 12.5 mm intervals, and the steel cords are coated with an unvulcanized rubber composition from both the upper and lower sides, which are immediately vulcanized at 160 ° C. for 20 minutes, and have a width of 12.5 mm. A sample of was prepared. Next, in accordance with ASTM-D 2229, each sample after vulcanization is pulled out of the steel cord of each sample, and the coated state of the rubber after pulling is visually observed, and the coverage is displayed as 0 to 100%. Thus, it was used as an index of initial adhesiveness and wet heat resistant adhesiveness. It shows that initial value adhesiveness and wet heat-resistant adhesiveness are so high that a numerical value is large. The initial adhesiveness was evaluated in the initial state after vulcanization, and the wet heat resistant adhesiveness was evaluated after aging under a wet heat condition of standing at a temperature of 70 ° C. and a humidity of 100% RH for 4 days.

Synthesis Example 1 [Synthesis of 2- (cyclohexyldithio) benzothiazole]
0.85 g (0.005 mol) of 2-mercaptobenzothiazole was added at 40-45 ° C. to 1.3 g (0.005 mol) of N- (cyclohexylthio) phthalimide in 65 mL of benzene. After stirring this reaction mixture for 0.5 to 1 hour, phthalimide was removed by filtration. After some of the benzene was evaporated under a nitrogen atmosphere, the reaction mixture was filtered again to remove more phthalimide.
The benzene solution was then extracted with a dilute aqueous solution of sodium hydroxide, and the extract was washed with water. After drying with a desiccant (sodium sulfate), the remaining benzene was removed by evaporation. The residue was substantially pure 2- (cyclohexyldithio) benzothiazole. Elemental analysis of the product showed 4.9% nitrogen and was nearly identical to 4.98% nitrogen calculated from 2- (cyclohexyldithio) benzothiazole C ₁₃ H ₁₅ NS ₃ .

Manufacturing method of steel cord A Composed of five steel wires plated with brass (thickness: 0.25 μm) with copper and zinc contents (Cu: 63 mass%, Zn: 37 mass%) in the entire brass plating layer A steel cord (twisted structure: 1 × 5 structure, steel wire strand diameter: 0.25 mm) was prepared, washed with a cobalt acetate aqueous solution (pH: 6.0) having a concentration of 10 g / L for 30 seconds, and then subjected to 50 ° C. For 1 minute to obtain steel cord A.
The cobalt concentration in the surface of the brass plating layer of the obtained steel cord A steel wire was 0.5% by mass, the phosphorus concentration was 1.0% by mass, and the zinc concentration was 5.0% by mass. .

Manufacturing method of steel cord B Steel cord B which was the same as steel cord A was obtained except that it was not washed. The cobalt concentration on the surface of the brass plating layer of the obtained steel cord A steel wire was 0.00 mass%, the phosphorus concentration was 3.0 mass%, and the zinc concentration was 20.0 mass%. .

Example 1 and Comparative Examples 1 to 4
Using a Banbury mixer with an internal volume of 2200 mL, each component shown in Table 1 was kneaded with the composition shown in Table 1 to prepare an unvulcanized rubber composition, and the above-described brass-plated steel cord A complex with A or B was prepared and the above-mentioned properties were determined. The results are shown in Table 1.

[note]
Steel cord A and steel cord B used were those obtained by the above manufacturing method.
1) HAF carbon black: Asahi Carbon Co., Ltd., trade name “Asahi # 70”
2) Cobalt fatty acid salt: manufactured by OMG, trade name “Manobond C22.5”, cobalt content 22.5% by mass
3) Anti-aging agent: N-phenyl-N′-1,3-dimethylbutyl-p-phenylenediamine, manufactured by Ouchi Shinsei Chemical Industry Co., Ltd., trade name “Noxeller 6C”
4) Thiazole compound: 2- (cyclohexyldithio) benzothiazole obtained in Synthesis Example 1 5) Vulcanization accelerator: N, N-dicyclohexyl-2-benzothiazolylsulfenamide, manufactured by Ouchi Shinsei Chemical Co., Ltd. Product name "Noxeller DZ"

  As can be seen from the results shown in Table 1, the rubber composition according to the present invention (Example 1) has a longer Mooney scorch time as compared with the rubber compositions of Comparative Examples 1 to 4, so that Excellent workability (workability). In addition, the rubber composition according to the present invention (Example 1) has better bloom resistance than the rubber composition of Comparative Example 1, it is easy to produce a rubber-steel composite, and is unvulcanized. Excellent workability. In addition, the rubber composition according to the present invention (Example 1) was good in both toughness (TF) after thermal deterioration and crack growth resistance as compared with the rubber compositions of Comparative Examples 1 to 4. . Furthermore, the rubber-steel composite (Example 1) of the present invention has both good initial adhesiveness and wet heat resistant adhesiveness as compared with the composites of Comparative Examples 1 to 4, and excellent adhesiveness. showed that.

  The rubber-steel composite of the present invention is excellent in adhesion between a rubber composition and a steel wire or a steel cord, that is, both initial adhesion and wet heat-resistant adhesion. It is suitable for reinforcing rubber articles such as belts and hoses that require particularly high strength.

Claims (17)

A rubber-steel composite comprising a rubber composition and a steel cord formed by twisting a plurality of steel wires or steel wires, wherein the rubber composition comprises (A) a rubber component, (B) sulfur ( C) a thiazole compound represented by the following general formula (1), wherein the steel wire has a brass plating layer on its peripheral surface, and excludes zinc and copper on the surface of the brass plating layer A rubber-steel composite having a transition metal concentration of 0.01% by mass or more.

(In the formula, R ^{1 to} R ⁴ are each independently a hydrogen atom, a linear alkyl group having 1 to 10 carbon atoms, a branched alkyl group having 3 to 12 carbon atoms, a linear alkoxy group having 1 to 10 carbon atoms, and carbon. R ⁵ is a group selected from a branched alkoxy group having 3 to 12. R ⁵ is a linear alkyl group having 1 to 10 carbon atoms, a branched alkyl group having 3 to 12 carbon atoms, an alicyclic hydrocarbon group, and an aromatic carbon group. (It is a group selected from a hydrogen group. N is an integer of 2 to 4.) 2. The rubber-steel composite according to claim 1, wherein R ^{1 to} R ⁴ in the general formula (1) are all hydrogen atoms. The rubber-steel composite according to claim 1 or 2, wherein R ⁵ in the general formula (1) is a group selected from a cycloalkyl group and an aralkyl group.   The rubber composition contains 0.1 to 5 parts by mass of a thiazole compound represented by the general formula (1) with respect to 100 parts by mass of the rubber component (A). A rubber-steel composite according to 1.   The rubber-steel composite according to any one of claims 1 to 4, wherein the rubber composition contains (B) 0.3 to 10 parts by mass of sulfur with respect to 100 parts by mass of the (A) rubber component.   The rubber-steel composite according to any one of claims 1 to 5, wherein a phosphorus concentration on the surface of the brass plating layer is 2.5 mass% or less and a zinc concentration is 15 mass% or less.   The rubber-steel composite according to any one of claims 1 to 6, wherein the transition metal is cobalt.   The rubber-steel composite according to any one of claims 1 to 7, wherein the rubber component (A) contains at least one of natural rubber and synthetic polyisoprene rubber.   The rubber-steel composite according to claim 8, wherein the rubber component (A) is composed of 50% by mass or more of natural rubber and 50% by mass or less of synthetic rubber.   The rubber-steel composite according to any one of claims 1 to 9, wherein the rubber composition does not contain a cobalt compound.   The rubber-steel composite according to any one of claims 1 to 11, wherein an average thickness of the brass plating layer is 0.13 to 0.30 µm.   The rubber-steel composite according to any one of claims 1 to 11, wherein a diameter of the steel wire is 0.40 mm or less.   The rubber-steel composite according to any one of claims 1 to 12, wherein the rubber composition covers the steel cord formed by twisting a plurality of the steel wires or the steel wires.   A tire comprising the rubber-steel composite according to claim 1.   A brass plating process for forming a brass plating layer on the peripheral surface of the steel wire, a wire drawing process for drawing the steel wire on which the brass plating layer is formed, and a surface of the drawn steel wire contain a transition metal compound. A method for producing a steel wire for a rubber-steel composite, comprising a washing step of washing with an aqueous solution.   The method for producing a steel wire for a rubber-steel composite according to claim 15, wherein the transition metal compound is a cobalt compound.   The steel wire for rubber-steel composite according to claim 16, wherein the cobalt compound is a compound selected from cobalt chloride, cobalt nitrate, cobalt sulfate, cobalt acetate, cobalt citrate, cobalt gluconate and cobalt acetylacetonate. Production method.