WO2023276641A1

WO2023276641A1 - Cord-rubber composite body, rubber product and method for producing cord-rubber composite body

Info

Publication number: WO2023276641A1
Application number: PCT/JP2022/023658
Authority: WO
Inventors: 良子神田; 英彰境田; 一樹奥野
Original assignee: 住友電気工業株式会社
Priority date: 2021-06-30
Filing date: 2022-06-13
Publication date: 2023-01-05
Also published as: CN117222791A; DE112022003318T5; US20240229351A1; JPWO2023276641A1

Abstract

A cord-rubber composite body (1) according to the present disclosure is provided with: one or more steel cords (10) each of which comprises a steel wire rod (2); and a rubber (4) which covers at least a part of the surface of each one of the steel cords (10). Each one of the steel cords (10) comprises the steel wire rod (2) and a metal nanoparticle layer (3) that is superposed on the surface of the steel wire rod (2). The metal nanoparticle layer (3) contains first metal nanoparticles and second metal nanoparticles; the first metal nanoparticles contain copper; and the second metal nanoparticles contain one or more substances that are selected from among zinc, cobalt, tin, iron, nickel, aluminum, and oxides of these elements.

Description

Cord-rubber composite, rubber product and method for producing cord-rubber composite

The present disclosure relates to cord-rubber composites, rubber products and methods of making cord-rubber composites.
This application claims priority based on Japanese Application No. 2021-109610 filed on June 30, 2021, and incorporates all the descriptions described in the above Japanese Application.

Various rubber reinforcing fiber materials are used in rubber products such as tires, and among these, steel cords using steel wire rods are widely used. For example, in the prior art, in a pneumatic steel radial rubber product having a carcass layer composed of a cord-rubber composite in which steel cords are embedded, the surfaces of the steel wires that make up the steel cords are given a predetermined brass plating. disclosed (see Patent Document 1). Since the steel cord is coated with a brass-plated layer (Cu--Zn alloy), an interfacial reaction between the brass-plated layer and the rubber occurs during vulcanization of the rubber to form a reaction layer (copper-sulfur layer). As a result, the brass plating layer and the rubber are bonded together.

JP-A-8-253004

The cord-rubber composite of the present disclosure includes one or more steel cords including steel wire rods, and rubber covering at least a portion of the surface of the steel cords, and the steel cords are combined with the steel wire rods. , having a metal nanoparticle layer laminated on the surface of the steel wire, the metal nanoparticle layer containing first metal nanoparticles and second metal nanoparticles, the first metal nanoparticles containing copper, The second metal nanoparticles contain one or more selected from zinc, cobalt, tin, iron, nickel, aluminum and oxides thereof.

The method for producing a cord-rubber composite of the present disclosure includes the steps of applying a metal nanoink containing metal nanoparticles and a solvent for dispersing the metal nanoparticles to the surface of a steel wire, and A step of drying the coating film of the metal nano-ink, a step of drawing the steel wire after the drying step, and a step of coating at least part of the surface of the steel cord formed after the drawing step with rubber. wherein the metal nanoparticles contain first metal nanoparticles and second metal nanoparticles, the first metal nanoparticles comprise copper, and the second metal nanoparticles are zinc, cobalt, tin, iron, nickel , aluminum and oxides thereof.

FIG. 1 is a schematic cross-sectional view of a cord-rubber composite according to one aspect of the present disclosure. FIG. 2 is a schematic partial cross-sectional view of a rubber product according to one aspect of the present disclosure.

[Problems to be Solved by the Present Disclosure]
In the above-mentioned cord-rubber composite, in which the brass-plated steel cord is embedded on the surface of the steel wire, the adhesion between the steel cord and the rubber is due to sulfur in the rubber and copper in the brass plating of the steel cord. reacts 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 on the surface from the fracture starting point, and adhesion may decrease.

In addition, in the conventional brass-plated steel wire manufacturing process, the hot diffusion plating method, in which zinc is plated on the copper-plated layer and then the brass-plated layer is formed by thermal diffusion, is generally adopted as a means of brass plating. It is In recent years, while various environmental problems have been emphasized, there is a growing movement worldwide to reduce carbon dioxide and move toward a low-carbon society.

The present disclosure has been made based on the above circumstances, and can produce a cord-rubber composite having excellent adhesion between rubber and steel cord, and a cord-rubber composite having excellent adhesion between rubber and steel cord. Another object of the present invention is to provide a method for producing a cord-rubber composite that can reduce carbon dioxide during production.

[Effect of the present disclosure]
A cord-rubber composite according to an aspect of the present disclosure has excellent adhesion between rubber and steel cords. According to the method for producing a cord-rubber composite according to another aspect of the present disclosure, it is possible to produce a cord-rubber composite having excellent adhesion between rubber and steel cord, and to reduce carbon dioxide during production. can be done.

[Description of Embodiments of the Present Disclosure]
First, the embodiments of the present disclosure are listed and described.

The cord-rubber composite has excellent adhesion between rubber and steel cord, and can contribute to the reduction of carbon dioxide during manufacturing. The reason why such an effect occurs is presumed as follows, for example. Since the metal nanoparticle layer laminated on the surface of the steel wire contains the first metal nanoparticles and the second metal nanoparticles, the copper- The sulfur layer exists three-dimensionally rather than planarly. As a result, the anchor effect can further improve the adhesiveness between the rubber and the steel cord. In addition, since the provision of the metal nanoparticle layer eliminates the need for a heat treatment process such as the thermal diffusion plating method, it can contribute to the reduction of carbon dioxide during production.

The second metal nanoparticles preferably contain zinc or zinc oxide. By including zinc or zinc oxide in the second metal nanoparticles, the adhesion between the rubber and the steel cord in the cord-rubber composite can be further improved.

The mass ratio of the total amount of the first metal nanoparticles to the total amount of the second metal nanoparticles in the metal nanoparticle layer is preferably 1 or more and 9 or less. When the mass ratio of the total amount of the first metal nanoparticles to the total amount of the second metal nanoparticles in the metal nanoparticle layer is within the above range, the adhesion between the rubber and the steel cord in the cord-rubber composite can be improved.

The average thickness of the metal nanoparticle layer is preferably 0.01 μm or more and 1.0 μm or less. When the average thickness of the metal nanoparticle layer is within the above range, the adhesion between the metal nanoparticle layer and rubber can be further improved.

The rubber product of the present disclosure includes the cord-rubber composite having excellent adhesion between rubber and steel cord. Therefore, the rubber product can have improved durability.

As described above, in the conventional brass-plated steel wire manufacturing process, the hot diffusion plating method is generally used as a means of brass plating, in which zinc is plated on the copper plating layer, and then the brass plating layer is formed by thermal diffusion. adopted by In such a process, thermal diffusion causes carbon dioxide to be emitted from the factory. In the method for producing the cord-rubber composite, the coating film of the metal nano-ink is dried on the surface of the steel wire, so a thermal diffusion process such as brass plating is unnecessary. Therefore, the cord-rubber composite production method can reduce carbon dioxide during production. In addition, in the method for producing the cord-rubber composite, the metal nanoink for forming the coating film contains the first metal nanoparticles and the second metal nanoparticles, so that the steel wire and the rubber In the above, the copper-sulfur layer of the first metal nanoparticles exists three-dimensionally, not planarly. As a result, the anchor effect can further improve the adhesiveness between the rubber and the steel cord. Therefore, the method for producing a cord-rubber composite can produce a cord-rubber composite having excellent adhesion between rubber and steel cord, and can reduce carbon dioxide during production.

In the method for producing the cord-rubber composite, it is preferable that the primary particles of the metal nanoparticles have a particle diameter of more than 10 nm and less than 150 nm, and a median diameter of 30 nm or more and 100 nm or less. When the particle diameter and median diameter of the primary particles of the metal nanoparticles 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 nanoparticles" include the first metal nanoparticles and the second metal nanoparticles.

Here, the "median diameter (D50)" is a value at which the volume-based integrated distribution calculated according to JIS-Z-8819-2 (2001) is 50%. The median diameter of the metal nanoparticles in the metal nanoink is calculated from the volume-based cumulative distribution measured by the laser diffraction method. After coating the metal nanoink, it can be calculated by analyzing an SEM (Scanning Electron Microscope) image. Specifically, it is calculated from the average value for two fields of 100,000-fold SEM images. By “nanoparticle” is meant a particle having an average particle size of less than 1 μm, calculated as one-half of the sum of the maximum microscopic length and the maximum width perpendicular to this length. . "Average thickness" means the value obtained by measuring the thickness at 10 arbitrary points and averaging the values.

[Details of the embodiment of the present disclosure]
<Cord-rubber composite>
A cord-rubber composite according to an embodiment of the present disclosure will be described in detail below.

The cord-rubber composite exists in a form included in the rubber product and functions as a reinforcing material for the rubber product. This cord-rubber composite does not require plating on the surface of the steel cord, but instead applies ink with dispersed nanoparticles, eliminating the need for a heat treatment process. of adhesion is obtained. Therefore, the steel cord of the present disclosure can improve the durability of rubber products.

FIG. 1 is a schematic cross-sectional view of the cord-rubber composite. The cord-rubber composite 1 has one or a plurality of steel cords 10 containing steel wire rods 2 and rubber (topping rubber) 4 covering at least part of the surface of the steel cords 10 . FIG. 1 shows a widthwise cross section of a steel cord 10 covered with rubber 4 . The steel wire rod 2 has a metal nanoparticle layer 3 laminated on its surface. That is, the metal nanoparticle layer 3 exists at the interface between the rubber 4 and the steel wire 2 .

(steel cord)
The steel cord 10 includes one or more steel wires 2 and a metal nanoparticle layer 3 laminated on the surface of the steel wires 2 . Here, in the cord-rubber composite 1, when there are a plurality of steel wires 2, the metal nanoparticle layer 3 may be laminated on the surfaces of only some of the plurality of steel wires 2.

〈Steel wire rod〉
The steel wire rod 2 is not particularly limited, but a high carbon steel wire is preferred. As the steel wire material 2, a plurality of strands twisted together at a constant pitch or a plurality of strands aligned in parallel without being twisted together can be used. When a twisted wire obtained by twisting a plurality of wires is used as the steel wire 2, the twisted structure of the steel wire 2 may be a single twist (1×N) in which N wires are twisted once. exemplified. The number N of single-twisted filaments can be set as appropriate. Another twisted structure of the steel wire 2 may be a laminar twist (N+M) in which M sheaths are wound around N cores in layers.

<Metal nanoparticle layer>
The cord-rubber composite 1 includes a metal nanoparticle layer 3 laminated on the surface of the steel wire 2 . The metal nanoparticle layer 3 can be formed by drying a coating film of metal nanoink containing metal nanoparticles. Applying an ink in which metal nanoparticles are dispersed eliminates the need for a heat treatment process, which contributes to the reduction of carbon dioxide during production.

In the metal nanoink for forming the metal nanoparticle layer 3, the metal nanoparticles contain first metal nanoparticles and second metal nanoparticles. The first metal nanoparticles contain copper. The second metal nanoparticles contain one or more selected from zinc, cobalt, tin, iron, nickel, aluminum and oxides thereof. The first metal nanoparticles and the second metal nanoparticles may be a single metal, or may form an alloy. Since the metal nanoparticle layer 3 contains the first metal nanoparticles and the second metal nanoparticles, the copper-sulfur layer of the first metal nanoparticles is flat between the steel wire 2 and the rubber 4. Instead, it exists three-dimensionally. As a result, the adhesiveness between the rubber 4 and the steel cord 10 can be further improved due to the anchor effect.

Combinations of the first metal nanoparticles and the second metal nanoparticles include, for example, 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.).

The second metal nanoparticles preferably contain zinc or zinc oxide. By including zinc or zinc oxide in the second metal nanoparticles, the adhesion between the rubber 4 and the steel cord 10 in the cord-rubber composite 1 can be further improved.

In the 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 or more and 9 or less, more preferably 1.5 or more and 4 or less, and 2 or more. 3 or less is more preferable. When the mass ratio of the first metal nanoparticles to the second metal nanoparticles is within the above range, the adhesion between the rubber 4 and the steel cord 10 in the cord-rubber composite 1 can be further improved.

The average aspect ratio of the metal nanoparticles in the metal nanoparticle layer 3 is preferably 1 or more and 20 or less, more preferably 1 or more and 10 or less, and even more preferably 1 or more and 5 or less. Adhesion between the rubber 4 and the steel cord 10 can be obtained by setting the average aspect ratio of the metal nanoparticles within the above range. The aspect ratio is measured using a cross-sectional image of the steel cord 10 by a transmission electron microscope (TEM). The “aspect ratio” is defined as A/B, where A is the maximum length of the metal nanoparticles in the wire drawing direction of the steel cord 10 and B is the maximum width perpendicular to the maximum length. It is an index representing the shape. "Average aspect ratio" means an average value obtained by measuring the aspect ratio at 10 points.

The lower limit of the average thickness of the metal nanoparticle layer 3 is preferably 0.01 μm, more preferably 0.02 μm. On the other hand, the upper limit of the average thickness of the metal nanoparticle layer 3 is preferably 1.0 μm, more preferably 0.8 μm. If the average thickness of the metal nanoparticle layer 3 is less than 0.01 μm, there is a possibility that sufficient adhesion between the steel cord 10 and the rubber 4 cannot be obtained due to the thin adhesive layer. On the other hand, if the average thickness of the metal nanoparticle layer 3 exceeds 1.0 μm, cracks may occur in the metal nanoparticle layer 3 and sufficient adhesion between the steel cord 10 and the rubber 4 may not be obtained.

The lower limit of the area ratio of the metal nanoparticles in the cross section of the metal nanoparticle layer 3 is preferably 50%, more preferably 60%. On the other hand, the upper limit of the area ratio of the metal nanoparticles in the cross section of the metal nanoparticle layer 3 is more preferably 100%. When the area ratio of the metal nanoparticles in the cross section of the metal nanoparticle layer 3 is within the above range, the anchor effect can be further exhibited, so that the adhesion between the rubber 4 and the steel cord 10 can be further improved.

(rubber)
The rubber (topping rubber) 4 that coats at least part of the surface of the steel cord 10 is not particularly limited, and a general rubber composition that has been conventionally used can be used. The rubber composition may contain, for example, a rubber component, a vulcanizing agent, a filler and other various additives.

Examples of rubber components include modified natural rubber such as natural rubber, epoxidized natural rubber, deproteinized natural rubber, isoprene rubber (IR), styrene-butadiene rubber (SBR), butadiene rubber (BR), acrylonitrile-butadiene rubber ( NBR), isoprene-isobutylene rubber (IIR), ethylene-propylene-diene rubber (EPDM), halogenated butyl rubber (HR), chloroprene rubber (CR), and various other synthetic rubbers. The rubber component may be a combination of multiple rubber components.

Examples of the vulcanizing agent include sulfur and sulfur-containing compounds. Examples of the filler include inorganic fillers such as carbon black and silica. Various chemicals generally used in rubber compositions can be used as the additive. Examples of the above additives include vulcanization accelerators, vulcanization retarders, process oils, antioxidants, organic acids, organic cobalt compounds, zinc oxide and the like.

The cord-rubber composite has excellent adhesion between rubber and steel cord. In addition, since the metal nanoparticle layer is provided without the brass plating layer, the heat treatment process becomes unnecessary, which can contribute to the reduction of carbon dioxide during production.

<Method for producing cord-rubber composite>
Next, a method for producing a cord-rubber composite according to an embodiment of the present disclosure will be described in detail.

A method for producing a cord-rubber composite according to an embodiment of the present disclosure includes a step of applying metal nano-ink containing metal nanoparticles and a solvent for dispersing the metal nanoparticles onto the surface of a steel wire (hereinafter referred to as coating a step of drying the metal nano-ink coating film applied to the steel wire (hereinafter also referred to as a drying step); and a step of drawing the steel wire after the drying step ( hereinafter also referred to as a wire drawing step), and a step of coating at least part of the surface of the steel cord formed after the wire drawing step with rubber (hereinafter also referred to as a rubber coating step).

[Coating process]
In the coating step, the steel wire is coated with the metal nano-ink described above.

(Metal nano ink)
A metal nanoink includes, for example, a solvent, metal nanoparticles dispersed in the solvent, and a dispersant.

(Metal nanoparticles)
The metal nanoparticles contained in the metal nanoink can be formed by a wave high-temperature treatment method, a liquid phase reduction method, a gas phase method, or the like. A liquid phase reduction method for precipitating is preferably used.

In the metal nanoink for forming the metal nanoparticle layer, the metal nanoparticles contain first metal nanoparticles and second metal nanoparticles. The first metal nanoparticles contain copper. The second metal nanoparticles contain one or more selected from zinc, cobalt, tin, iron, nickel, aluminum and oxides thereof. Since the details of the metal nanoparticles are as described above, the description is omitted.

The range of the particle size of the primary particles of the metal nanoparticles is preferably more than 10 nm and less than 150 nm, more preferably more than 10 nm and less than 100 nm, and even more preferably 30 nm or more and less than 80 nm. If the primary particle size of the metal nanoparticles is less than 10 nm, for example, the dispersibility and stability of the metal nanoparticles in the metal nanoink may be reduced. On the other hand, when the particle size of the primary particles of the metal nanoparticles exceeds 150 nm, the gaps between the metal nanoparticles become large, which may make it impossible to form a dense metal nanoparticle layer.

The lower limit of the median diameter of the primary particles of the metal nanoparticles is preferably 30 nm, more preferably 50 nm. On the other hand, the upper limit of the median diameter of the primary particles of the metal nanoparticles is preferably 100 nm, more preferably 80 nm. If the median diameter of the primary particles of the metal nanoparticles is less than 30 nm, for example, the dispersibility and stability of the metal nanoparticles in the metal nanoink may be reduced. On the other hand, when the median diameter of the primary particles of the metal nanoparticles is 100 nm, the voids in the metal nanoparticle layer formed become large, and there is a risk that sufficient adhesion between the steel cord and the rubber cannot be obtained.

In order to adjust the particle size of the metal nanoparticles, the type and blending ratio of the metal compound, dispersant, and other additives are adjusted, and the stirring speed, temperature, time, pH, etc. in the reduction step of reducing the metal compound are controlled. should be adjusted.

(solvent)
The solvent for the metal nanoink is not particularly limited, but water is preferably used, and an organic solvent may be blended with water.

Various water-soluble organic solvents can be used as the organic solvent to be blended in the metal nanoink. 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 methyl ethyl ketone; Examples include polyhydric alcohols such as ethylene glycol and glycerin, other esters, and glycol ethers such as ethylene glycol monoethyl ether and diethylene glycol monobutyl ether.

The content of water, which is the solvent in the metal nanoink, is preferably 20 parts by mass or more and 1900 parts by mass or less per 100 parts by mass of the metal nanoparticles. If the water content is less than 20 parts by mass, the concentration of the metal nanoparticles becomes too high, and there is a risk that uniform coating with the metal nanoink will not be possible. On the other hand, when the content of water exceeds 1900 parts by mass, the proportion of metal nanoparticles in the metal nanoink is reduced, and a good metal having the thickness and density required for the surface of the steel wire rod of the cord-rubber composite. A nanoparticle layer may not be formed.

(dispersant)
The metal nanoink may further contain a dispersant, for example. Examples of the dispersant include polyethylene glycol, polyvinyl alcohol, and polymeric materials of polycarboxylic acid.

The content of the dispersant is preferably 0.5 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the metal nanoparticles. The dispersant surrounds the metal nanoparticles to prevent aggregation and disperse the metal nanoparticles well. may become On the other hand, if the content of the dispersant exceeds 20 parts by mass, the excessive dispersant may reduce the adhesion between the steel wire and the metal nanoparticle layers.

In addition to the dispersant described above, the metal nanoink may contain other additives within a range that does not impede these effects. Other additives include, for example, ascorbic acid and amine-based polymers.

The method for producing metal nanoink includes, for example, a step of depositing metal nanoparticles by a liquid phase reduction method, a step of separating the metal nanoparticles deposited in the step of depositing the metal nanoparticles, and a step of separating the metal nanoparticles. A step of dispersing the metal nanoparticles obtained in the separating step in the solvent, and a step of adding a dispersant and other additives to the dispersion liquid prepared in the dispersing step.

The method of applying metal nano-ink to steel wire is not particularly limited. As the coating method, conventionally known coating methods 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 and a dip coating method can be used.

[Drying process]
In the drying step, the metal nano-ink coating film on the steel wire is dried. After the coating step, the metal nano-ink can be dried by cold air drying or natural drying. Therefore, no heating is required in the drying process. The wind speed of the cold air is preferably set to a level that does not make the coating film rippling. A specific wind speed of the cold air on the coating film surface can be, for example, 5 m/sec or more and 10 m/sec or less.

[Wire drawing process]
In the wire drawing step, the steel wire after the drying step is drawn. Through this process, the steel cord can have the desired size and strength. In the method for producing the cord-rubber composite, wire drawing can be performed without heating after the ink is applied. Regarding the wire drawing process, wire drawing conditions and the like are not particularly limited as long as the wire drawing is performed according to a conventional method using a wire drawing machine normally used in the wire drawing process of steel wire rods.

In addition, when performing wet wire drawing using a liquid lubricating liquid in the wire drawing process, metal nanoparticles can be mixed in the liquid lubricating liquid, and the coating process and the wire drawing process can be performed at the same time.

[Rubber coating process]
In the rubber coating step, at least part of the surface of the steel cord formed after the wire drawing step is coated with rubber. The method of coating the steel cord with rubber is also not particularly limited, and known methods can be used. For example, it can be manufactured by arranging steel cords in parallel at regular intervals, embedding the steel cords in a rubber composition, and then vulcanizing the steel cords. Examples of rubber compositions include compositions containing rubber components, vulcanizing agents, fillers and other various additives, as described above.

According to the method for producing a cord-rubber composite, it is possible to produce a cord-rubber composite with excellent adhesion between rubber and steel cord, and to reduce carbon dioxide during production.

<Rubber products>
The rubber product includes the cord-rubber composite having excellent adhesion between rubber and steel cord. Therefore, the rubber product can have improved durability. Examples of such rubber products include tires, hoses, and conveyor belts. FIG. 2 is a schematic partial cross-sectional view of a rubber product according to one aspect of the present disclosure. The rubber product 50 shown in FIG. 2 includes the cord-rubber composite 1 . FIG. 2 shows a longitudinal section of the cord-rubber composite 1 embedded in the rubber substrate 8 of the rubber product 50. As shown in FIG. In the rubber product 50, a plurality of the cord-rubber composites 1 are embedded in the rubber base material 8, thereby forming a skeleton of a portion that requires durability such as repeated bending, for example. .

When manufacturing a tire as the rubber product of the present disclosure, for example, the steel cord of the present disclosure is embedded in a sheet-like unvulcanized rubber made of a rubber composition to obtain a reinforcing belt structure. As the rubber composition used for the rubber product, for example, the same rubber compositions as those exemplified for the above rubber can be used. Thereafter, the reinforcing belt structure and the tire constituent members are bonded together, set in a vulcanizer, and vulcanized by pressing, heating, etc., to obtain a tire as a rubber composite. As a result, a tire with excellent durability can be manufactured.

The embodiments disclosed this time should be considered illustrative in all respects and not restrictive. The scope of the present invention is not limited to the configuration of the above-described embodiment, but is indicated by the scope of the claims, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims. be.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

　In order to verify the effects of the present disclosure, Test No. 1 provided with a steel cord having a metal nanoparticle layer. 1 and test no. Two cord-rubber composites were made.

<Test No. 1>
First, a metal nanoink containing metal nanoparticles with a weight ratio of zinc oxide and copper of 1:3 was prepared. Next, the metal nano-ink was applied to the surface of a steel wire rod cut to a diameter of φ1 mm and a length of 150 mm to a length of 75 mm from the tip, and the coating film was dried to prepare 30 steel cords. After that, 30 steel cords were embedded in rubber and vulcanized at 165° C. for 18 minutes. No. 1 cord-rubber composite was made. Test no. Observation of the cross section of No. 1 with a transmission electron microscope confirmed a metal nanoparticle layer at the interface between the steel wire and the rubber. The average thickness of the metal nanoparticle layer was 0.05 μm.

<Test No. 2>
Copper plating and zinc plating were sequentially applied to the surface of a steel wire material having a diameter of φ1 mm and a wire diameter of 150 mm, and a brass plating layer was laminated by performing thermal diffusion treatment at 600° C. for 10 seconds. The composition of the brass plating layer was such that the mass ratio of zinc and copper was 1:3. Other test no. Wire drawing was performed in the same manner as in 1 to prepare 30 steel cords. After that, 30 steel cords were embedded in rubber and vulcanized at 165° C. for 18 minutes. Two cord-rubber composites were made. Test no. Observation of the cross section of No. 2 with a transmission electron microscope confirmed a uniform brass plating layer at the interface between the steel wire rod and the rubber. The average thickness of the brass plating layer was 0.25 μm.

[evaluation]
(Evaluation of adhesion between steel cord and rubber)
After holding for 5 days in an environment of 80° C. and 95% RH, the steel cord was peeled off from the rubber, and the percentage of rubber remaining on the surface of the steel cord was measured. The adhesion between the steel cord and the rubber was evaluated on a scale of A to D. The evaluation criteria for the adhesiveness were as follows. If the evaluation of adhesiveness is from A to C, it is considered acceptable. Table 1 shows the evaluation results.
A: 90% by mass or more B: 75% by mass or more C: 40% by mass or more D: less than 40% by mass

As shown in Table 1, Test No. provided with steel cords laminated with metal nanoparticle layers containing first metal nanoparticles and second metal nanoparticles. The cord-rubber composite of No. 1 had excellent adhesion between the steel cord and the rubber.
On the other hand, Test No. 1 was provided with a steel cord in which copper plating and zinc plating were sequentially applied to the surface of a steel wire material, and a brass plating layer was laminated by performing thermal diffusion treatment. 2 cord-rubber composite was tested in test no. The adhesion was inferior to that of the cord-rubber composite of No. 1.

As the above results show, the cord-rubber composite has excellent adhesion between rubber and steel cord, and does not require heat diffusion treatment unlike the brass plating layer, which reduces carbon dioxide emissions during manufacturing. can be planned.

1 cord - rubber composite 2 steel wire rod 3 metal nanoparticle layer 4 rubber (topping rubber)
8 rubber substrate 10 steel cord 50 rubber product

Claims

one or more steel cords comprising steel wire;
and rubber covering at least part of the surface of the steel cord,
The steel cord has the steel wire and a metal nanoparticle layer laminated on the surface of the steel wire,
The metal nanoparticle layer contains first metal nanoparticles and second metal nanoparticles,
the first metal nanoparticles comprise copper;
A cord-rubber composite in which the second metal nanoparticles include one or more selected from zinc, cobalt, tin, iron, nickel, aluminum and oxides thereof.
The cord-rubber composite according to claim 1, wherein the second metal nanoparticles contain zinc or zinc oxide.
The cord-rubber composite according to claim 1 or claim 2, wherein the mass ratio of the total amount of the first metal nanoparticles to the total amount of the second metal nanoparticles in the metal nanoparticle layer is 1 or more and 9 or less. .
The cord-rubber composite according to claim 1, claim 2, or claim 3, wherein the metal nanoparticle layer has an average thickness of 0.01 μm or more and 1.0 μm or less.
A rubber product comprising the cord-rubber composite according to any one of claims 1 to 4.
a step of applying a metal nanoink containing metal nanoparticles and a solvent for dispersing the metal nanoparticles onto the surface of the steel wire;
a step of drying the coating film of the metal nano-ink applied to the steel wire;
a step of drawing the steel wire after the drying step; and a step of covering at least part of the surface of the steel cord formed after the drawing step with rubber,
The metal nanoparticles contain first metal nanoparticles and second metal nanoparticles,
the first metal nanoparticles comprise copper;
A method for producing a cord-rubber composite, wherein the second metal nanoparticles include one or more selected from zinc, cobalt, tin, iron, nickel, aluminum and oxides thereof.
7. The method for producing a cord-rubber composite according to claim 6, wherein the primary particles of the metal nanoparticles have a particle diameter of more than 10 nm and less than 150 nm, and a median diameter of 30 nm or more and 100 nm or less.