The present disclosure relates to a cord-rubber composite, a rubber product, and a method of manufacturing a cord-rubber composite. This application claims priority based on Japanese Patent Application No. 2021-109610 filed on Jun. 30, 2021, and the entire contents of the Japanese patent application are incorporated herein by reference.
Various fiber-reinforced rubber materials are used in rubber products such as tires, and among them, steel cords using steel wires are widely used. For example, in the related art, in a pneumatic steel-radial rubber product including a carcass layer formed of a cord-rubber composite in which steel cords are embedded, it is disclosed that predetermined brass plating is performed on a surface of a steel wire constituting the steel cord (see PTL 1). Since the steel cord is covered with the brass plating layer (Cu—Zn alloy), an interfacial reaction between the brass plating layer and the rubber occurs during rubber vulcanization, thereby forming a reaction layer (copper-sulfur layer). This results in adhesion between the brass plating layer and the rubber.
PTL 1: Japanese Unexamined Patent Application Publication No. 8-253004
A cord-rubber composite of present disclosure includes one or more steel cords each including a steel wire, and rubber covering at least a part of a surface of each of the one or more steel cords. The one or more steel cords each include the steel wire and a metal nanoparticle layer stacked on a surface of the steel wire, the metal nanoparticle layer contains a first metal nanoparticle and a second metal nanoparticle, the first metal nanoparticle contains copper, and the second metal nanoparticle contains one or two or more selected from zinc, cobalt, tin, iron, nickel, aluminum, and oxides thereof.
A method of manufacturing a cord-rubber composite according to the present disclosure includes coating a surface of a steel wire with a metal nano-ink containing a metal nanoparticle and a solvent in which the metal nanoparticle is dispersed; drying a coating film of the metal nano-ink coated to the steel wire; drawing the steel wire after the drying; and covering at least a part of a surface of a steel cord formed after the drawing with rubber. The metal nanoparticle contains a first metal nanoparticle and a second metal nanoparticle, the first metal nanoparticle contains copper, and the second metal nanoparticle contains one or two or more selected from zinc, cobalt, tin, iron, nickel, aluminum, and oxides thereof.
In the cord-rubber composite in which the steel cord having the brass plating applied to the surface of the steel wire is embedded, the adhesion between the steel cord and the rubber is formed by the reaction between sulfur in the rubber and copper in the brass plating of the steel cord to form an adhesive layer. In the conventional manufacturing process, since the copper-sulfur layer, which is the reaction layer, is a uniform film, if there is a defect, peeling is likely to occur at the surface from the fracture starting point, and there is a possibility that the adhesion is lowered.
In addition, in a process of manufacturing a conventional brass plating steel wire, a thermal diffusion plating method in which zinc plating is performed on a copper plating layer and then a brass plating layer is formed by thermal diffusion is generally adopted as a means of brass plating. In recent years, while various environmental problems are regarded as important, the reduction of carbon dioxide and the movement to a low-carbon society are increasing worldwide.
The present disclosure has been made in view of the above circumstances, and an object thereof is to provide a cord-rubber composite having excellent adhesion between the rubber and the steel cord, and a method of manufacturing a cord-rubber composite capable of manufacturing a cord-rubber composite having excellent adhesion between the rubber and the steel cord and reducing carbon dioxide during manufacturing.
The cord-rubber composite according to an embodiment of the present disclosure has excellent adhesion between the rubber and the steel cord. According to the method of manufacturing a cord-rubber composite according to another aspect of the present disclosure, it is possible to manufacture a cord-rubber composite having excellent adhesion between the rubber and the steel cord and to reduce carbon dioxide during manufacturing.
First, embodiments of the present disclosure will be listed and explained.
A cord-rubber composite of present disclosure includes one or more steel cords each including a steel wire, and rubber covering at least a part of a surface of each of the one or more steel cords. The one or more steel cords each include the steel wire and a metal nanoparticle layer stacked on a surface of the steel wire, the metal nanoparticle layer contains a first metal nanoparticle and a second metal nanoparticle, the first metal nanoparticle contains copper, and the second metal nanoparticle contains one or two or more selected from zinc, cobalt, tin, iron, nickel, aluminum, and oxides thereof.
The cord-rubber composite has excellent adhesion between the rubber and the steel cord, and can contribute to reduction of carbon dioxide during manufacturing. The reason why such an effect occurs is presumed as follows, for example. Since the metal nanoparticle layer stacked on the surface of the steel wire contains the first metal nanoparticle and the second metal nanoparticle, the copper-sulfur layer of the first metal nanoparticle is not present in a planar shape but in a three dimensional shape between the steel wire and the rubber. As a result, the adhesion between the rubber and the steel cord can be further improved by the anchoring effect. In addition, since the metal nanoparticle layer is provided, a heat treatment process such as a thermal diffusion plating method is not required. Therefore, it can contribute to reduction of carbon dioxide during manufacturing.
The second metal nanoparticle preferably contains zinc or an oxide of zinc. When the second metal nanoparticle contains zinc or the oxide of zinc, the adhesiveness between the rubber and the steel cord in the cord-rubber composite can be further improved.
A mass ratio of a total amount of the first metal nanoparticle to a total amount of the second metal nanoparticle in the metal nanoparticle layer is preferably 1 to 9. When the mass ratio of the total amount of the first metal nanoparticle to the total amount of the second metal nanoparticle in the metal nanoparticle layer is within the above range, the adhesiveness between the rubber and the steel cord in the cord-rubber composite can be further improved.
The metal nanoparticle layer preferably has an average thickness of 0.01 μm to 1.0 μm. When the metal nanoparticle layer has the average thickness within the above range, the adhesion between the metal nanoparticle layer and the rubber can be further improved.
A rubber product of the present disclosure includes the cord-rubber composite having excellent adhesion between the rubber and the steel cord. Therefore, the rubber product can have improved durability.
A method of manufacturing a cord-rubber composite according to the present disclosure, the method includes coating a surface of a steel wire with a metal nano-ink containing a metal nanoparticle and a solvent in which the metal nanoparticle is dispersed; drying a coating film of the metal nano-ink coated to the steel wire; drawing the steel wire after the drying; and covering at least a part of a surface of a steel cord formed after the drawing with rubber. The metal nanoparticle contains a first metal nanoparticle and a second metal nanoparticle, the first metal nanoparticle contains copper, and the second metal nanoparticle contains one or two or more selected from zinc, cobalt, tin, iron, nickel, aluminum, and oxides thereof.
As described above, in the process of manufacturing the conventional brass plating steel wire, a thermal diffusion plating method in which zinc plating is performed on a copper plating layer and then a brass plating layer is formed by thermal diffusion is generally adopted as a means for brass plating. In such a process, carbon dioxide is discharged from the factory by thermal diffusion. In the method of manufacturing the cord-rubber composite, since the coating film of metal nano-ink on the surface of the steel wire is dried, a thermal diffusion process such as brass plating is not required. Therefore, the method of manufacturing the cord-rubber composite can reduce carbon dioxide during manufacturing. In addition, in the method of manufacturing the cord-rubber composite, since the metal nano-ink for forming the coating film contains the first metal nanoparticles and the second metal nanoparticles, the copper-sulfur layer of the first metal nanoparticles is not present in a planar shape but in a three dimensional shape between the steel wire and the rubber. As a result, the adhesion between the rubber and the steel cord can be further improved by the anchoring effect. Therefore, the method of manufacturing the cord-rubber composite can produce the cord-rubber composite having excellent adhesion between the rubber and the steel cord, and can reduce carbon dioxide during manufacturing.
In the method of manufacturing the cord-rubber composite, a primary particle of the metal nanoparticle preferably has a particle diameter of more than 10 nm and less than 150 nm and a median diameter of 30 nm to 100 nm. When the particle diameter and the median diameter of the primary particle of the metal nanoparticle are within the above ranges, the dispersibility and stability of the metal nanoparticles can be improved, and the adhesion between the steel cord and the rubber can be improved. The “metal nanoparticle” includes the first metal nanoparticle and the second metal nanoparticle.
Here, the “median diameter (D50)” is a value at which the volume-based cumulative distribution calculated in accordance with JIS-Z-8819-2 (2001) is 50%. The median diameter of the metal nanoparticle in the metal nano-ink is calculated from a cumulative distribution on a volume basis measured by a laser diffraction method. After coating the metal nano-ink, it can be calculated by analyzing an SEM (Scanning Electron Microscope) image. Specifically, it is calculated from an average value of two visual fields of an SEM image magnified 100,000 times. The term “nanoparticle” refers to a particle having an average particle diameter of less than 1 μm, the average particle diameter being calculated as one half of the sum of the maximum length and the maximum width in a direction perpendicular to the length direction as determined by microscopic observation. The term “average thickness” refers to a value obtained by measuring the thickness at arbitrary 10 points and averaging the measured thicknesses.
Hereinafter, a cord-rubber composite according to an embodiment of the present disclosure will be described in detail.
The cord-rubber composite is included in the rubber product and functions as a reinforced material of the rubber product. In the cord-rubber composite, the surface of the steel cord is not plated but coated with an ink in which nanoparticles are dispersed, so that a heat treatment process is not required and adhesion with the rubber equal to or higher than that of a conventional brass-diffusion plated steel wire is obtained. Thus, the steel cord of the present disclosure can improve the durability of rubber products.
Steel cord 10 includes one or more steel wires 2 and metal nanoparticle layer 3 stacked on a surface of steel wire 2. Here, in cord-rubber composite 1, when there are a plurality of steel wires 2, metal nanoparticle layer 3 may be stacked on the surface of only a part of the plurality of steel wires 2.
Steel wire 2 is not limited to the specific wire, but is preferably a high carbon steel wire. As steel wire 2, a wire in which a plurality of element wires are twisted at a constant pitch or a wire in which a plurality of element wires are arranged in parallel without being twisted can be used. When a stranded element wire in which a plurality of element wires are twisted is used as steel wire 2, a single-stranded structure (1×N) in which N element wires are stranded once is exemplified as the stranded structure of steel wire 2. The number N of filaments in the single-stranded structure can be set as appropriate. Another stranded structure of steel wire 2 may be a layer-stranded structure (N+M) in which M sheaths are wound around N cores in a layered manner.
Cord-rubber composite 1 includes metal nanoparticle layer 3 stacked on a surface of steel wire 2. Metal nanoparticle layer 3 may be formed by drying a coating film of metal nano-ink containing metal nanoparticles. By coating the ink in which the metal nanoparticles are dispersed, the heat treatment process becomes unnecessary, and it is possible to contribute to reduction of carbon dioxide during manufacturing.
In the metal nano-ink for forming metal nanoparticle layer 3, the metal nanoparticles contain first metal nanoparticles and second metal nanoparticles. The first metal nanoparticle contains copper. The second metal nanoparticle contains one or two or more selected from zinc, cobalt, tin, iron, nickel, aluminum, and oxides thereof. The first metal nanoparticle and the second metal nanoparticle may be a single metal or may form an alloy. Since metal nanoparticle layer 3 contains the first metal nanoparticles and the second metal nanoparticles, the copper-sulfur layer of the first metal nanoparticles is not present in s planar shape but in a three dimensional shape between steel wire 2 and rubber 4. As a result, the adhesion between rubber 4 and steel cord 10 can be further improved by the anchoring effect.
Examples of the combination of the first metal nanoparticle and the second metal nanoparticle include copper and zinc oxide, copper and zinc, copper and zinc and cobalt, copper and zinc oxide and cobalt, copper and cobalt, copper and cobalt oxide (CoO, Co2O3, Co3O4, etc.), copper and tin, copper and tin oxide (SnO, SnO2, SnO3, etc.), and the like.
The second metal nanoparticle may contain zinc or an oxide of zinc. When the second metal nanoparticle contains zinc or an oxide of zinc, the adhesiveness between rubber 4 and steel cord 10 in cord-rubber composite 1 can be further improved.
In metal nanoparticle layer 3, the mass ratio of the total amount of the first metal nanoparticles to the total amount of the second metal nanoparticles is preferably 1 to 9, more preferably 1.5 to 4, and still more preferably 2 to 3. When the mass ratio of the first metal nanoparticles to the second metal nanoparticles is within the above range, the adhesion between rubber 4 and steel cord 10 in cord-rubber composite 1 can be further improved.
The average aspect ratio of the metal nanoparticles in metal nanoparticle layer 3 is preferably 1 to 20, more preferably 1 to 10, and still more preferably 1 to 5. When the average aspect ratio of the metal nanoparticles is within the above range, the adhesion between rubber 4 and steel cord 10 can be obtained. The aspect ratio is measured using a cross-sectional image of steel cord 10 obtained by a transmission electron microscope (TEM). The “aspect ratio” is an index representing the shape of the metal nanoparticle represented by A/B, where A is the maximum major diameter of the metal nanoparticle in the drawing direction of steel cord 10 and B is the maximum width perpendicular to the maximum major diameter. “Average aspect ratio” means a value obtained by measuring the aspect ratio at 10 points and averaging the measured values.
The lower limit of the average thickness of metal nanoparticle layer 3 is preferably 0.01 μm, and more preferably 0.02 μm. On the other hand, the upper limit of the average thickness of metal nanoparticle layer 3 is preferably 1.0 μm, and more preferably 0.8 μm. When metal nanoparticle layer 3 has the average thickness of less than 0.01 μm, sufficient adhesion between steel cord 10 and rubber 4 may not be obtained because the adhesive layer is thin. On the other hand, when metal nanoparticle layer 3 has the average thickness of more than 1.0 μm, cracks may occur in metal nanoparticle layer 3 and sufficient adhesion between steel cord 10 and rubber 4 may not be obtained.
The lower limit of the area ratio of the metal nanoparticles in the cross section of metal nanoparticle layer 3 is preferably 50%, and more preferably 60%. On the other hand, the upper limit of the area ratio of the metal nanoparticles in the cross section of metal nanoparticle layer 3 is more preferably 100%. When the area ratio of the metal nanoparticles in the cross-section of metal nanoparticle layer 3 is within the above range, the anchoring effect can be further achieved, and thus the adhesion between rubber 4 and steel cord 10 can be further improved.
Rubber (topping rubber) 4 covering at least a part of the surface of steel cord 10 is not limited to the specific rubber, and a general rubber composition conventionally used may be used. The rubber composition may include, for example, a rubber component, a vulcanizing agent, a filler material, and other various additives.
Examples of the rubber components include natural rubber, modified natural rubber such as epoxidized natural rubber and deproteinized natural rubber, and various synthetic rubber such as isoprene rubber (IR), styrene-butadiene rubber (SBR), butadiene rubber (BR), acrylonitrile-butadiene rubber (NBR), isopreneisobutylene rubber (IIR), ethylene-propylene-diene rubber (EPDM), halogenated butyl rubber (HR), and chloroprene rubber (CR). The rubber component may be a combination of a plurality of rubber components.
Examples of the vulcanizing agent include sulfur and sulfur-containing compounds. Examples of the filler material include carbon black and inorganic filler materials such as silica. As the additive, various chemicals generally used in rubber compositions can be used. Examples of the additive include a vulcanizing accelerator, a vulcanizing retardant, a process oil, an antioxidant, an organic acid, an organic cobalt compound, and zinc oxide.
The cord-rubber composite has excellent adhesion between the rubber and the steel cord. In addition, since the brass plating layer is not included and the metal nanoparticle layer is included, a heat treatment process is not necessary, and thus it is possible to contribute to reduction of carbon dioxide during manufacturing.
Next, a method of manufacturing a cord-rubber composite according to an embodiment of the present disclosure will be described in detail.
A method of manufacturing a cord-rubber composite according to an embodiment of the present disclosure includes coating a surface of a steel wire with a metal nano-ink containing metal nanoparticles and a solvent in which the metal nanoparticles are dispersed (hereinafter, also referred to as a coating process); drying a coating film of the metal nano-ink coated to the steel wire (hereinafter also referred to as a drying process); drawing the steel wire after the drying process (hereinafter, also referred to as a drawing process); covering at least a part of a surface of a steel cord formed after the drawing process with rubber (hereinafter, also referred to as rubber-covering process).
In the coating process, the metal nano-ink is coated on the steel wire.
The metal nano-ink includes, for example, a solvent, metal nanoparticles dispersed in the solvent, and a dispersant.
The metal nanoparticles contained in the metal nano-ink can be formed by a high-temperature treatment method, a liquid-phase reduction method, a gas-phase method, or the like. Among them, the liquid-phase reduction method in which metal ions are reduced by a reducing agent in an aqueous solution to precipitate metal nanoparticles is preferably used.
In the metal nano-ink for forming the metal nanoparticle layer, the metal nanoparticle contains a first metal nanoparticle and a second metal nanoparticle. The first metal nanoparticle contains copper. The second metal nanoparticle contains one or two or more selected from zinc, cobalt, tin, iron, nickel, aluminum, and oxides thereof. The details of the metal nanoparticle are as described above, and thus description thereof is omitted.
Primary particle of the metal nanoparticle may has the range of the particle diameter of preferably more than 10 nm and less than 150 nm, more preferably more than 10 nm and less than 100 nm, and still more preferably 30 nm or more and less than 80 nm. When primary particle of the metal nanoparticle has the particle diameter of less than 10 nm, for example, the dispersibility and stability of the metal nanoparticle in the metal nano-ink may be deteriorated. On the other hand, when the particle diameter of the primary particle of the metal nanoparticle is more than 150 nm, the gaps between the metal nanoparticles become large, and thus a dense metal nanoparticle layer may not be formed.
The lower limit of the median diameter of the primary particle of the metal nanoparticle is preferably 30 nm, and more preferably 50 nm. On the other hand, the upper limit of the median diameter of the primary particle of the metal nanoparticle is preferably 100 nm, and more preferably 80 nm. When primary particle of the metal nanoparticle has the median diameter of less than 30 nm, for example, the dispersibility and stability of the metal nanoparticle in the metal nano-ink may be deteriorated. On the other hand, when the primary particle of the metal nanoparticle has the median diameter more than 100 nm, the void in the formed metal nanoparticle layer becomes large, and sufficient adhesion between the steel cord and the rubber may not be obtained.
In order to adjust the particle diameter of the metal nanoparticles, the types and blending ratios of the metallic compound, dispersant, and other additives may be adjusted, and the stirring speed, temperature, time, pH, and the like in the reduction process in which the metallic compound is subjected to a reduction reaction may be adjusted.
The solvent of the metal nano-ink is not limited the specific solvent, but water is preferably used, and an organic solvent may be mixed with water.
As the organic solvent to be mixed with the metal nano-ink, various water-soluble organic solvents can be used. Specific examples thereof include alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, sec-butyl alcohol, and tert-butyl alcohol; ketones such as acetone and methylethyl ketone; polyhydric alcohols such as ethyleneglycol and glycerin; other esters; and glycol ethers such as ethyleneglycol monoethyl ether and diethyleneglycol monobutyl ether.
The content ratio of water as a solvent in the metal nano-ink is preferably 20 parts by mass to 1900 parts by mass with respect to 100 parts by mass of the metal nanoparticles. When the content ratio of the water is less than 20 parts by mass, the concentration of the metal nanoparticles becomes too high, and there is a concern that uniform coating with the metal nano-ink cannot be performed. On the other hand, when the content ratio of the water is more than 1900 parts by mass, the ratio of the metal nanoparticles in the metal nano-ink decreases, and there is a concern that a good metal nanoparticle layer having a necessary thickness and density cannot be formed on the surface of the steel wire of the cord-rubber composite.
The metal nano-ink may further contain, for example, a dispersant. Examples of the dispersant include polymer materials such as polyethylene glycol, polyvinyl alcohol, and polycarboxylic acid.
The content ratio of the dispersant is preferably 0.5 parts by mass to 20 parts by mass with respect to 100 parts by mass of the metal nanoparticles. The dispersant surrounds the metal nanoparticles to prevent aggregation and satisfactorily disperse the metal nanoparticles. However, when the content of the dispersant is less than 0.5 parts by mass, the effect of preventing aggregation may be insufficient. On the other hand, when the content of the dispersant is more than 20 parts by mass, the adhesion between the steel wire and the metal nanoparticle layer may be deteriorated due to the excessive dispersant.
The metal nano-ink may contain other additives in addition to the above dispersant as long as these effects are not inhibited. Examples of the other additives include ascorbic acid and amine-based polymers.
A method of manufacturing a metal nano-ink includes, for example, a process of precipitating metal nanoparticles by a liquid-phase reduction method, a process of separating the metal nanoparticles precipitated in the process of precipitating the metal nanoparticles, a process of dispersing the metal nanoparticles obtained in the process of separating the metal nanoparticles in the solvent, and a process of adding a dispersant and other additives to the dispersion liquid prepared in the process of dispersing.
The method of coating the steel wire with the metal nano-ink is not limited to the specific method. As the coating method, for example, a conventionally known coating method such as a spin-coating method, a spray-coating method, a bar-coating method, a die-coating method, a slit-coating method, a roll-coating method or a dip-coating method can be used.
In the drying process, the metal nano-ink coating film on the steel wire is dried. After the coating process, the metal nano-ink can be dried by cold air drying or natural drying. Therefore, heating is not required in the drying process. The air velocity of the cold air is preferably set to such an extent that the coating film is not waved. A specific wind velocity of the cold air on the coating film surface can be, for example, from 5 m/second to 10 m/second.
In the drawing process, the steel wire after the drying process is drawn. In this process, the steel cord can have a desired size and strength. In the method of manufacturing a cord-rubber composite, wire drawing can be performed without heating after coating ink. As for the drawing process, the drawing conditions and the like are not particularly limited as long as the drawing process is performed according to a conventional method using a wire drawing machine which is usually used in the drawing process of steel wire.
When wet drawing using a lubricating liquid is performed in the drawing process, the coating process and the drawing process can be performed at the same time by mixing metal nanoparticles in the lubricating liquid.
In the rubber-covering process, at least a part of the surface of the steel cord formed after the drawing process is covered with rubber. The method of covering the steel cord with the rubber is not limited to the specific method, and a known method can be used. For example, it can be produced by arranging steel cords in parallel at regular intervals, embedding the steel cords in the rubber composition, and vulcanizing the rubber composition. As described above, examples of the rubber composition include compositions containing a rubber component, a vulcanizing agent, a filler material, and other various additives.
According to the method of manufacturing the cord-rubber composite, the cord-rubber composite having excellent adhesion between the rubber and the steel cord can be produced, and carbon dioxide can be reduced during manufacturing.
The rubber product includes the cord-rubber composite having excellent adhesion between the rubber and the steel cord. Therefore, the rubber product can have improved durability. Such rubber products include, for example, tires, hoses, conveyor belts and the like.
When a tire is manufactured as the rubber product of the present disclosure, for example, the steel cords of the present disclosure are embedded in a sheet-like unvulcanized rubber of the rubber composition to obtain a reinforced belt structure. As the rubber composition used in the rubber product, for example, the same rubber composition as exemplified in the rubber can be used. Thereafter, the reinforced belt structure and the tire constituting member are bonded to each other and set in a vulcanizing machine, and a vulcanizing treatment is performed by applying pressing, heating and the like to obtain a tire as a rubber product. Accordingly, a tire having excellent durability can be manufactured.
It should be understood that the embodiments disclosed herein are illustrative in all respects and are not restrictive. The scope of the present invention is not limited to the configurations of the above-described embodiments, but is defined by the scope of the claims and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.
Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.
In order to verify the effect of the present disclosure, cord-rubber composites of Test No. 1 and Test No. 2 including steel cords having a metal nanoparticle layer were prepared.
First, a metal nano-ink containing metal nanoparticles in which a mass ratio of zinc oxide and copper was 1:3 was prepared. Next, the surfaces of steel wires cut into lengths of 150 mm with diameters of φ 1 mm were coated with the metal nano-ink from the tips to the 75 mm lengths, and the coating films were dried to produce 30 steel cords. Thereafter, 30 steel cords were embedded in rubber and vulcanized at 165° C. for 18 minutes to prepare a cord-rubber composite of Test No. 1. When the cross section of Test No. 1 was observed with a transmission electron microscope, a metal nanoparticle layer could be confirmed at the interface between the steel wire and the rubber. The average thickness of the metal nanoparticle layer was 0.05 μm.
Copper plating and zinc plating were sequentially applied to surfaces of steel wires having diameters of q 1 mm and lengths of 150 mm, and a brass plating layer was stacked by performing thermal diffusion treatment at 600° ° C. for 10 seconds. In the composition of the brass plating layer, the mass ratio of zinc and copper was 1 : 3. Wire drawing was performed in the same manner as in Test No. 1 except for the above, and 30 steel cords were produced. Thereafter, 30 steel cords were embedded in rubber and vulcanized at 165° C. for 18 minutes to prepare a cord-rubber composite of Test No. 2. When the cross section of Test No. 2 was observed with a transmission electron microscope, a uniform brass plating layer was confirmed at the interface between the steel wire and the rubber. The average thickness of the brass plating layer was 0.25 μm.
After the steel cord was held in an environment of 80° C. and RH 95% for 5 days, the steel cord was peeled off from the rubber, and the ratio of the rubber remaining on the surface of the steel cord was measured. The adhesion between the steel cord and the rubber was evaluated in four grades of A to D. The evaluation criteria for the adhesiveness were as follows. When the evaluation of the adhesiveness is A to C, it is regarded as passing. The evaluation results are shown in Table 1.
As shown in Table 1, the cord-rubber composite of Test No. 1 including the steel cord on which the metal nanoparticle layer containing the first metal nanoparticles and the second metal nanoparticles was stacked had excellent adhesion between the steel cord and the rubber. On the other hand, the cord-rubber composite of Test No. 2 including the steel cord in which the brass plating layer was stacked by sequentially applying copper plating and zinc plating on the surface of the steel wire and performing the thermal diffusion treatment was inferior in adhesion to the cord-rubber composite of Test No. 1.
As can be seen from the above results, the cord-rubber composite has excellent adhesion between the rubber and the steel cord and does not require a thermal diffusion treatment such as a brass plating layer, so that carbon dioxide can be reduced during manufacturing.
Number | Date | Country | Kind |
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2021-109610 | Jun 2021 | JP | national |
Filing Document | Filing Date | Country | Kind |
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PCT/JP2022/023658 | 6/13/2022 | WO |