Bead wire, bead bundle, and tire

Abstract

Provided is a bead wire including a steel wire, a metal coating layer covering the steel wire, and a thermoplastic resin layer covering the metal coating layer, in which the thermoplastic resin layer contains sulfur. The present invention improves the problem of raw rubber stickiness of a bead wire during manufacturing of a bead bundle for a tire. The invention also provides a bead bundle and a tire.

Description

Technical Field

[0001] The present invention relates to a bead wire for a tire. The present invention also relates to a bead bundle or a tire including the bead wire. Background Art

[0002] A bead wire is a wire used to manufacture a bead bundle for reinforcing a tire bead. Generally, the bead wire has a metal coating, such as a coating of brass, bronze or zinc, which is used to bond to the vulcanized rubber composite material of the tire. The wire has a cross-section that is circular or polygonal (including flat shapes, rectangles or squares). Sometimes the bead wire has a resin layer on the metal coating. In some cases, the bead wire has a thin raw rubber composite material layer on the resin coating, or the bead wire directly has a thin raw rubber composite material layer on the metal coating. During the manufacture of the bead bundle, the thin raw rubber composite material layer on the bead wire causes adjacent bead wires to bond to each other to avoid slippage of the filaments, thereby stabilizing the shape of the bead bundle.

[0003] WO2014 / 102031 discloses a bead wire having a resin layer, and the resin layer includes a corrosion inhibitor. The corrosion inhibitor is used to improve the corrosion resistance of the bead wire.

[0004] US5176957 discloses a bead wire that has a bronze coating and a rubber composite material coating on the bronze coating, and the bronze coating has a specific weight ratio of Cu and Sn for improving the adhesion between the bead wire and the vulcanized rubber composite material coating. "Adhesion" occurs between the metal coating and the vulcanized rubber composite material that has undergone a cross-linking reaction to form a three-dimensional network structure.

[0005] The thin raw rubber composite material layer is coated by an extrusion method. However, during the manufacture of the bead bundle, it is found that the thin raw rubber composite material layer cannot be coated very uniformly on the resin layer, so that part of the surface of the bead wire is not covered by the raw rubber composite material. This is the so-called "green tack" problem, and "green tack" is the adhesion property between the bead wire and the raw rubber composite material that has not undergone a cross-linking reaction. Therefore, adjacent bead wires may not adhere to each other due to insufficient coverage of the raw rubber composite material on the bead wire, and the risk of filament slippage is increased, which brings trouble to the manufacture of the bead bundle. Summary of the Invention

[0006] The main object of the present invention is to solve the problems of the prior art.

[0007] A first object of the present invention is to provide a bead wire that has good green tack performance through a raw rubber composite material.

[0008] A second object of the present invention is to provide a bead bundle including bead wires.

[0009] A third object of the present invention is to provide a tire including bead wires.

[0010] According to the first object of the present invention, there is provided a bead wire including a wire, a metal coating covering the wire, and a thermoplastic resin layer covering the metal coating, wherein the thermoplastic resin layer contains sulfur.

[0011] The present invention is beneficial to the next process of bead bundle manufacturing, particularly the step of coating a raw rubber composite layer on the thermoplastic resin layer of the bead wire. The raw rubber composite layer is coated on the bead wire by extrusion at a temperature of 65°C to 95°C. Then, at least a part or all of the thermoplastic resin of the thermoplastic resin layer penetrates into the boundary region of the extruded raw rubber composite layer. The "boundary region" refers to the part of the raw rubber composite layer close to or even in contact with the metal coating. By adding sulfur to the thermoplastic resin layer, as the thermoplastic resin penetrates into the raw rubber composite layer, sulfur is relatively evenly dispersed in the boundary region of the raw rubber composite layer. The sulfur dispersed in the boundary region of the raw rubber composite layer will react with the metal coating of the bead wire, and then metal sulfide is relatively evenly generated in the boundary region of the raw rubber composite layer. And this metal sulfide has a dendritic structure beneficial to anchoring and bonding the raw rubber composite to the bead wire. Therefore, the raw rubber composite adheres more to the bead wire, and the coverage rate of the extruded raw rubber composite on the surface of the bead wire is increased, and the problem that there is no raw rubber composite on the bead wire even after extrusion and even after passing through a series of guide pulleys is significantly reduced. The problem of raw rubber stickiness is reduced. The bead wires adhere to each other better. Therefore, the bead bundle made of the bead wire having a resin layer and a raw rubber composite layer will have improved shape stability and reduce the risk of wire slippage within the bead bundle.

[0012] The sulfur in the thermoplastic resin layer can be detected by X-ray photoelectron spectroscopy (XPS).

[0013] The content of sulfur is greater than 0% and less than 40%, expressed as the atomic percentage relative to the total amount of oxygen, iron, sulfur, nitrogen, and metal of the metal coating determined by XPS. More preferably, the content of sulfur ranges between 5% and 25%, expressed as the atomic percentage relative to the total amount of oxygen, iron, sulfur, nitrogen, and metal of the metal coating determined by XPS.

[0014] The sulfur can be soluble sulfur or insoluble sulfur. Preferably, the sulfur is soluble sulfur.

[0015] According to the present invention, the softening point of the thermoplastic resin for the thermoplastic resin layer is from 70°C to 125°C. Preferably, the softening point of the thermoplastic resin for the thermoplastic resin layer is from 70°C to 115°C. More preferably, the softening point of the thermoplastic resin for the thermoplastic resin layer is from 70°C to 95°C. The "softening point" is a property of the resin, which is the temperature at which the resin begins to soften. The "softening point" is a property different from the "glass transition temperature" which is a property of the polymer, and the "glass transition temperature" is the temperature at which the glassy state changes to the highly elastic state.

[0016] The thermoplastic resin can be any one of the existing thermoplastic resins for bead wires. The thermoplastic resin can be a hydrocarbon resin or a phenolic resin, including coumarone resins, petroleum resins, terpene resins, asphalt and rosin, their salts, esters and other derivatives and modifications. Preferably, the thermoplastic resin is a coumarone resin or a petroleum resin. The molecular weight of the thermoplastic resin according to the present invention is not more than 2000. The thermoplastic resin generally does not have double bonds, so that even when the temperature is up to 125°C or even higher, it will not crosslink with sulfur. Therefore, the sulfur-containing thermoplastic resin layer is a mixture, which means that there is no chemical reaction between sulfur and the thermoplastic resin.

[0017] According to the present invention, the metal coating can be any one of the existing metal coatings for bead wires. Preferably, the metal coating is a zinc, zinc alloy, copper or copper alloy coating. The copper alloy coating can be a brass or bronze coating. Ternary or quaternary metal alloy coatings are also available.

[0018] The bead wire further has a rubber composite layer on the thermoplastic resin layer. Here, the rubber composite layer is a raw rubber composite layer.

[0019] According to the second object of the present invention, there is provided a bead bundle, the bead bundle including a bead ring, the bead ring including at least one bead wire of the present invention, the bead wire of the present invention including a wire, a metal coating covering the wire and a thermoplastic resin layer covering the metal coating, wherein the thermoplastic resin layer contains sulfur.

[0020] Preferably, the bead wire is coated with a raw rubber composite layer on the thermoplastic resin layer, so that the bead wire in the bead bundle has a raw rubber composite layer as the outer layer.

[0021] The bead ring can be any one of the existing types of bead rings, and the bead ring has a cross-section in a circular, square, rectangular, quadrilateral or hexagonal shape.

[0022] The rubber composite layer is an unvulcanized raw rubber composite layer. A "raw rubber composite layer" refers to an unvulcanized rubber composite layer, which means that crosslinking has not occurred in the raw rubber composite layer. The raw rubber composite layer can be any of the existing raw rubber composite layers coated on the bead wire.

[0023] The bead bundle optionally has one or more layers coated on the bead ring for fixing and stabilizing the shape of the bead ring, namely, a rubber layer, a fabric covering layer, and / or a polymer layer.

[0024] According to the third object of the present invention, there is provided a tire including a pair of bead bundles of the present invention or including a pair of bead bundles each including at least one bead wire of the present invention.

[0025] Due to the vulcanization of the tire, the raw rubber composite layer of the bead wire in the tire becomes a vulcanized rubber composite layer. Description of the Drawings

[0026] Figure 1 The cross-section of the bead wire is described.

[0027] Figure 2 The POF test results are described. Detailed Description of the Invention

[0028] The manufacture of the bead wire starts with the wire. The wire can be any of the existing wires used for bead wires. Then the wire is coated with any of the existing metal coatings, such as bronze, brass, or zinc coatings.

[0029] A thermoplastic resin, such as coumarone resin or petroleum resin, with a softening point of 70°C to 95°C is prepared. The thermoplastic resin is dissolved in an existing known organic solvent to prepare a thermoplastic resin solution, and the organic solvent can be acetone, gasoline, ethyl acetate, or a mixture thereof. Then sulfur (i.e., soluble sulfur or insoluble sulfur) is added to the thermoplastic resin solution. Ensure that the sulfur is relatively evenly distributed in the thermoplastic resin solution.

[0030] Then the thermoplastic resin solution is coated on the wire by extrusion. The wire is dried to evaporate the organic solvent. Thus, the manufacture of the bead wire of the present invention is completed.

[0031] Then, a raw rubber composite layer is coated on the bead wire by extrusion for the manufacture of the bead bundle. The raw rubber composite layer is used to promote the bonding or adhesion of adjacent bead wires to each other to prevent wire slippage, thereby stabilizing the shape of the bead bundle.

[0032] The present invention improves the coverage rate of the extruded raw rubber composite layer on the surface of the resin layer of the bead wire. The larger the coverage rate of the raw rubber composite layer, the better the bonding or adhesion performance of the bead wire.

[0033] A pull-out force (POF) test was conducted to understand the raw rubber tackiness performance of the bead wire of the present invention. The POF test was carried out according to ASTM D2229. One difference is that the bulk sample of the raw rubber composite of the bead wire was not vulcanized, but the bulk sample of the raw rubber composite was heated to 80 °C for 15 min to simulate the raw rubber tackiness mode, and the rest was the same. The bead wire of the present invention is a bronze-coated bead wire with a coumarone resin layer, and the softening point of the coumarone resin layer is about 85 °C to 90 °C. The coumarone resin layer contains 10% sulfur (expressed as the atomic percentage relative to the total amount of oxygen, iron, sulfur, nitrogen, copper, and tin determined by XPS). Figure 1 The cross-section of the bead wire 100 of the present invention is shown. The bead wire has a wire 105, a bronze coating 110, and a coumarone resin layer 120, and the coumarone resin layer 120 contains sulfur (not shown). Reference 1 is a bronze-coated bead wire without a resin layer, and reference 2 is a bronze-coated bead wire with a coumarone resin layer. The softening point of the coumarone resin layer is about 85 °C to 90 °C, and the coumarone resin layer does not contain sulfur. The POF test was carried out using the bead wire of the present invention, reference 1, and reference 2. Figure 2 The curve in shows the test results. Obviously, the bead wire of the present invention has better raw rubber tackiness performance than reference 1 and reference 2, and the POF measurement value of the bead wire of the present invention is much higher than the POF measurement values of reference 1 and reference 2.

[0034] According to the present invention, the softening point of the thermoplastic resin is measured according to the Chinese standard GB / T 12007.6-1989 "Epoxy resins-Determination of softening point-Ring and ball method".

[0035] XPS analysis can easily identify various elements including oxygen, sulfur, copper, zinc, tin, iron, and nitrogen. From the outermost surface of the thermoplastic resin layer to the sputtering time of 120 s, the atoms of oxygen, iron, sulfur, nitrogen, and metals (such as copper and zinc in the brass coating, copper and tin in the bronze coating, or zinc in the zinc coating) of the metal coating are measured. The equipment can be a K-Alpha X-ray photoelectron spectroscopy system available from Thermo Fisher Scientific. According to the kinetic energy distribution of the emitted electrons, information about the detected atoms is obtained: the number of elements (the energy position of the peak) and the number of atoms present (the height of the peak). The elements to be retained are predetermined according to the type of the metal coating, and the number of the predetermined elements is retained. The sputtering time is 120 s, the beam spot size is 300 μm, and the sputtering depth is related to the sputtering time: (For α-Fe). Calculate and record the atomic percentages of sulfur relative to the total amounts of oxygen, iron, sulfur, nitrogen, and metal in the metal coating at sputtering times of 0 s, 6 s, 12 s, 30 s, 60 s, 90 s, and 120 s. Exclude the sulfur atomic percentage values at sputtering times of 0 s and 6 s to avoid surface S contamination. Select the sulfur atomic percentage values at sputtering times of 12 s, 30 s, 60 s, 90 s, and 120 s, and calculate the average of these five selected values as the sulfur content of the thermoplastic resin layer of the bead wire, expressed as the atomic percentage relative to the total amounts of oxygen, iron, sulfur, nitrogen, and metal in the metal coating. In the case where the bead wire has a raw rubber composite layer on the thermoplastic resin layer, the raw rubber composite layer should be removed before XPS analysis.

[0036] The second embodiment is a bead wire having a bronze coating and a petroleum resin layer on the bronze coating. The petroleum resin layer contains 16% sulfur (expressed as the atomic percentage relative to the total amounts of oxygen, iron, sulfur, nitrogen, copper, and tin determined by XPS), and the softening point of the petroleum resin is 70°C to 95°C.

[0037] The third embodiment is a bead wire having a zinc coating and a coumarone resin layer on the zinc coating. The coumarone resin layer has 11% sulfur (expressed as the atomic percentage relative to the total amounts of oxygen, iron, sulfur, nitrogen, and zinc determined by XPS), and the softening point of the coumarone resin is 70°C to 95°C.

[0038] The fourth embodiment is a bead bundle. The bead bundle is a cable bead. All the wires of the cable bead have a bronze coating and a coumarone resin layer on the bronze coating. The coumarone resin layer contains 25% sulfur (expressed as the atomic percentage relative to the total amounts of oxygen, iron, sulfur, nitrogen, copper, and tin determined by XPS), and the wires have a raw rubber composite layer on the coumarone resin layer.

[0039] The fifth embodiment is a tire having a pair of bead bundles of the fourth embodiment.

Claims

1. A bead wire, the bead wire comprising a steel wire, a metal coating covering the steel wire, and a thermoplastic resin layer covering the metal coating, wherein, the thermoplastic resin layer contains sulfur.

2. The bead wire according to claim 1, wherein, the content of sulfur is greater than 0% and less than 40%, expressed as an atomic percentage relative to the total amount of oxygen, iron, sulfur, nitrogen, and metal in the metal coating determined by X-ray photoelectron spectroscopy.

3. The bead wire according to claim 2, wherein, the content of sulfur ranges from 5% to 25%, expressed as an atomic percentage relative to the total amount of oxygen, iron, sulfur, nitrogen, and metal in the metal coating determined by X-ray photoelectron spectroscopy.

4. The bead wire according to any one of claims 1 to 3, wherein, the softening point of the thermoplastic resin for the thermoplastic resin layer is 70°C to 125°C.

5. The bead wire according to claim 4, wherein, the softening point of the thermoplastic resin for the thermoplastic resin layer is 70°C to 115°C.

6. The bead wire according to claim 5, wherein, the softening point of the thermoplastic resin for the thermoplastic resin layer is 70°C to 95°C.

7. The bead wire according to any one of claims 1 to 6, wherein, the thermoplastic resin for the thermoplastic resin layer is a coumarone resin or a petroleum resin.

8. The bead wire according to any one of claims 1 to 7, wherein, the molecular weight of the thermoplastic resin for the thermoplastic resin layer is not greater than 2000.

9. The bead wire according to any one of claims 1 to 8, wherein, the metal coating is a zinc, zinc alloy, copper, or copper alloy coating.

10. The bead wire according to claim 9, wherein, the copper alloy coating is a brass or bronze coating.

11. The bead wire according to any one of claims 1 to 10, wherein, the thermoplastic resin layer containing sulfur is a mixture.

12. A bead bundle, the bead bundle comprising a bead ring, the bead ring including at least one bead wire according to any one of claims 1 to 10, the bead wire being coated with a raw rubber composite layer on the thermoplastic resin layer.

13. A tire, the tire comprising a pair of bead bundles, each of the pair of bead bundles including at least one bead wire according to any one of claims 1 to 10 or a bead bundle according to claim 11 or 12.

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