Retread tire

Abstract

To provide a retreaded tire having excellent durability in repeated use.SOLUTION: A retreaded tire comprises: a base tire comprising a carcass and a belt from an inner side in a tire radial direction; and retreaded rubber disposed on an outer side in the radial direction of the base tire. In the retreaded tire, an outermost belt layer in the tire radial direction comprises: a reinforcement element comprising a metal filament; and cross-linked rubber covering the reinforcement element. In addition, metal forming the metal filament is steel with a surface covered with ternary plating of copper, zinc, and iron.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to retread tires.

Background Art

[0002] Conventionally, in order to improve the fuel efficiency of automobiles, it has been required to further reduce the rolling resistance of tires. Since the rolling resistance of a tire can be reduced by decreasing the heat generation property of the entire tire, it has been required to decrease the heat generation property of the tire. In order to decrease the heat generation property of a tire, mainly, improvement of the formulation of a tread rubber composition has been carried out. As a method for reducing the amount of heat generation, using carbon black with low reinforcing properties or reducing the amount of carbon black can be considered, but the required performance, durability, deteriorates. Therefore, rubber with low heat generation property and excellent durability has been required.

[0003] In order to improve the durability of a tire, improvement of the crack growth resistance of the coating rubber composition in a tire belt layer has been required. For example, Patent Document 1 discloses a proposal for improving belt durability by incorporating a bisphenol compound into a belt coating rubber formulation to improve the adhesion performance and aging resistance to a steel cord. In order to improve the durability of a tire, attempts have also been made to improve the fracture resistance of a belt under cushion rubber. For example, Patent Document 2 discloses that a belt under cushion rubber contains 0.5 to 10 parts by weight of polymethoxymethylmelamine having 3 to 6 methoxymethyl groups and 0 to 3 methylol groups per 100 parts by weight of a diene rubber. Patent Document 3 proposes that a belt under cushion rubber contains a rubber component composed of a diene rubber and 1.5 to 4.0 parts by mass of total sulfur per 100 parts by mass of the rubber component, contains zinc oxide so that the mass ratio (zinc oxide / total sulfur) is 2.0 or more, and contains an organic acid.

[0004] In recent years, due to the increasing demand for resource conservation considering environmental impacts, retread technology that reuses worn-out tires has attracted attention. Retread technology is a technology that replaces the tread part of a used tire with a new tread part. In such tires, especially, a casing tire with high durability is required to enable multiple retreads. As a method for vulcanizing a tire in two stages, for example, in Patent Document 4, the molding and vulcanization process of the tire is divided into two mutually independent method steps A and B. In method step A, assembly is performed so as to include at least one carcass layer and a maximum part of the tread strip as the outermost layer in the radial direction. Subsequently, vulcanization treatment is carried out in a vulcanization mold that gives a predetermined cross-sectional contour to the surface and also to one or a plurality of strength carriers. This tire part is vulcanized in the same manner in method step B and then assembled into a completed tire, and a manufacturing method has been proposed.

[0005] In Patent Document 5, in a method for manufacturing a tire, a partial tire is formed in method step A and this partial tire is subsequently vulcanized. In method step B, a method is proposed in which the partial tire is added with all or the remaining part of the unvulcanized tread and then vulcanized to become a completed tire. In particular, a method for manufacturing a tire in which the surface of all or the remaining part of the unvulcanized tread is at least partially plasma-treated is disclosed. Furthermore, in Patent Document 6, a two-stage vulcanization method is adopted for a passenger car tire. After integrating the spiral belt layer and the tread, a first-stage vulcanization process of imprinting a tread pattern, and a second-stage vulcanization process of externally fitting the first-stage vulcanizate obtained in this first-stage vulcanization process to the outer periphery of the radial carcass ply of the case side member and then vulcanization molding are included, and a method for manufacturing a tire has been proposed.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Summary of the Invention

Problems to be Solved by the Invention

[0007] As one of the means for improving the durability of a tire, improvement in the durability of the belt layer, that is, improvement in the adhesion between the steel cords constituting the belt layer and the covering rubber has been cited, but there has still been room for improvement. In view of the above circumstances, an object of the present invention is to provide a retread tire excellent in durability in repeated use, and solving this object is an issue.

Means for Solving the Problems

[0008] <1> In a casing tire having a carcass and a belt, and a retread tire having retread rubber disposed on the outer side in the radial direction of the casing tire, starting from the inner side in the radial direction of the tire, the belt layer at the outermost layer in the radial direction of the tire includes a reinforcing element made of a metal filament and a crosslinked rubber covering the reinforcing element, and the metal constituting the metal filament is steel whose surface is coated with a ternary plating of copper, zinc, and iron, a retread tire.

[0009] <2> The retread tire according to <1>, wherein the amount of iron in the coating is 1% by mass or more and less than 10% by mass of the total mass of the copper, the zinc, and the iron. <3> The retread tire according to <1> or <2>, wherein the amount of phosphorus in the coating exceeds 0 mg / m 2 and is 4 mg / m 2 or less. <4> The retread tire according to any one of <1> to <3>, wherein the reinforcing element is wire-drawing processed by a diamond die.

[0010] <5> The retread tire according to any one of <1> to <4>, wherein the thickness of the crosslinked rubber before crosslinking that coats the reinforcing element is 0.4 to 1.0 times the wire diameter of the reinforcing element. <6> The retread tire according to any one of <1> to <5>, wherein the content of the cobalt-containing compound in the rubber composition constituting the crosslinked rubber is 0.01% by mass or less. <7> The retread tire according to any one of <1> to <6>, wherein the thickness of the crosslinked rubber that coats the reinforcing element is 0.4 to 1.0 mm. <8> The retread tire according to any one of <1> to <7>, wherein the content of cobalt atoms is 1% by mass or less.

Advantages of the Invention

[0011] According to the present invention, it is possible to provide a retread tire excellent in durability in repeated use.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

[0013] Hereinafter, the present invention will be illustrated and described in detail based on its embodiments. In the following description, the description of "A to B" indicating a numerical range represents a numerical range including the endpoints A and B, and represents "A or more and B or less" (when A < B), or "A or less and B or more" (when A > B). Also, parts by mass and mass% are synonymous with parts by weight and weight%, respectively.

[0014] The retread tire of the present invention is a retread tire having a carcass and a belted tire from the inner side in the tire radial direction and a retread rubber disposed on the outer side in the radial direction of the belted tire, wherein the belt layer at the outermost layer in the tire radial direction includes a reinforcing element made of a metal filament and a crosslinked rubber covering the reinforcing element, and the metal constituting the metal filament is steel whose surface is coated with a ternary plating of copper, zinc, and iron.

[0015] Generally, a retread tire buffs and the like the worn parts around the tread during running, removes unnecessary substances, forms a belted tire mainly composed of crosslinked rubber, attaches an unvulcanized retread rubber composition to this belted tire, and vulcanizes it under predetermined conditions for repeated use. As described above, since the retread tire is repeatedly used by replacing the retread rubber, the belted tire is required to have high durability. One of the important factors for maintaining the high durability of the belted tire is the high adhesiveness between the steel cord constituting the belt layer and the crosslinked rubber. In the present invention, by using a steel cord whose surface is coated with a ternary plating of copper, zinc, and iron as the reinforcing element contained in the belt layer, it is possible to achieve high adhesiveness. Even if the retread of removing the worn tread and forming the tread again is carried out a plurality of times, since the metal-crosslinked rubber adhesiveness is maintained well, the retread tire of the present invention is excellent in durability in repeated use.

[0016] <Structure of Retread Tire> FIG. 1 is a schematic cross-sectional view of a retread tire according to a preferred embodiment of the present invention. Hereinafter, the retread tire may be simply referred to as a tire. In the retread tire 1 shown in FIG. 1, from the inner side in the tire radial direction (downward in the figure, the same applies hereinafter), there is a casing tire having carcass 4 and belt 5, and a tread-shaped retread rubber 8 disposed on the outer side in the tire radial direction (upward in the figure, the same applies hereinafter) of the casing tire. More specifically, in the retread tire 1, stiffeners 3 and 3' extend from a pair of bead cores 2 and 2' respectively to the outer side in the tire radial direction. The stiffener 3 is folded back by the bead core 2 from the outside of the stiffener 3 to form a horseshoe-shaped tire case shape, and is folded back by the bead core 2' on the opposite side and locked outside the stiffener 3'. A belt 5 composed of a plurality of belt layers (4 layers of 5a to 5d in FIG. 1) is disposed on the outer side in the tire radial direction of the carcass 4 to form a casing tire. The belt layers 5a to 5d are arranged, for example, as the innermost belt layer 5a, the inner belt layer 5b forming an intersecting layer, the outer belt layer 5c forming an intersecting layer, and the outermost belt layer 5d. Usually, a belt wedge rubber 6 is disposed between the vicinity of the end of the inner belt layer 5b forming an intersecting layer and the vicinity of the end of the outer belt layer 5c forming an intersecting layer.

[0017] In the present invention, among the four belt layers constituting the belt 5, at least the outermost belt layer 5d in the tire radial direction includes a reinforcing element made of a metal filament and a crosslinked rubber covering the reinforcing element, and the metal constituting the metal filament is steel whose surface is coated with a ternary plating of copper, zinc, and iron. With the outermost belt layer 5d having such a configuration, the retread tire 1 (particularly, the casing tire) can exhibit excellent durability even when repeatedly used. Any one or more of the belt layers 5a to 5c may have the same structure as the belt layer 5d.

[0018] On the outer side in the tire radial direction of the belt 5, a tread-shaped retread rubber 8 is disposed via a cushion rubber layer 7. Also, on the outside of the carcass 4, a sidewall rubber 9 is disposed between the retread rubber 8 having a tread shape and the stiffener 3. The portion where the sidewall rubber 9 is disposed is referred to as side M, and the inner side in the tire radial direction of side M is referred to as bead N. In bead N, bead cores 2 and 2', stiffeners 3 and 3', etc. are disposed. An inner liner 10 is disposed inside the carcass 4 as an air permeation prevention layer.

[0019] In manufacturing the retread tire 1, for example, an uncrosslinked rubber composition for retread rubber, which is a raw material of the retread rubber 8, may be processed into a tread shape, disposed on the casing tire A, and vulcanized. Alternatively, as shown in FIG. 2, the retread rubber 8 having a tread shape prepared by pre-crosslinking may be adhered to the casing tire A as a precure tread member B.

[0020] FIG. 2 is a schematic cross-sectional view showing an example of the casing tire A and the precure tread member B. The casing tire A is formed by vulcanizing a case portion including at least the belt 5, side M, bead N, and base tread 8b'. Usually, a part of the tread rubber is disposed as a thin layer on the outer side in the tire radial direction of the belt 5 in the casing tire A. This is for improving the adhesion to the precure tread member B.

[0021] In the present invention, the thickness (T1) of the crosslinked rubber covering the reinforcing element when uncrosslinked refers to the thickness (T1) of the uncrosslinked rubber in the uncrosslinked rubber-metal composite covering the reinforcing element in a state where the crosslinked rubber is uncrosslinked rubber.

[0022] The thickness (T1) of the uncrosslinked rubber will be described more specifically with reference to FIG. 3. FIG. 3 is a partial cross-sectional schematic view of the uncrosslinked rubber-metal composite 20. The uncrosslinked rubber-metal composite 20 has three reinforcing elements 22a to 22c (collectively referred to as "reinforcing element 22") and an uncrosslinked rubber R1 covering the reinforcing element 22. One surface of the uncrosslinked rubber-metal composite 20 is S1, and the other surface is S2. "The thickness of the unvulcanized rubber coating the reinforcing element" (the thickness of the unvulcanized rubber) is synonymous with the layer thickness T1 of the coating layer (unvulcanized rubber R1) that coats the reinforcing element 22 of the unvulcanized rubber-metal composite 20 in Fig. 3. The layer thickness T1 is calculated by measuring the interlayer rubber spacing between two intersecting layers in the cross-section of the unvulcanized rubber-metal composite 20 and dividing it by two. That is, it is the shortest distance from the broken line S3 connecting the centers of the reinforcing elements 22 to the surface S1 or S2 of the unvulcanized rubber-metal composite 20, which is T1a or T1b in Fig. 3. Usually, in order to check for uneven strength of the unvulcanized rubber-metal composite 20, T1a and T1b are of the same length. If they are different, the layer thickness T1 is calculated as the average value of T1a and T1b. The layer thickness T1 can be measured with a micrometer by cutting out a sheet from the roll during the manufacture of the reinforcing layer.

[0023] Also, the definition of the thickness of the vulcanized rubber will be described with reference to Fig. 4. Fig. 4 is a partial cross-sectional schematic view of the vulcanized rubber-metal composite 21. The vulcanized rubber-metal composite 21 has three reinforcing elements 22a to 22c and a vulcanized rubber R2 that coats the reinforcing element 22. Let one surface of the vulcanized rubber-metal composite 21 be S4 and the other surface be S5. "The thickness of the vulcanized rubber coating the reinforcing element" is synonymous with the layer thickness T2 of the coating layer (vulcanized rubber R2) that coats the reinforcing element 22 of the vulcanized rubber-metal composite 21 in Fig. 4. The layer thickness T2 is the shortest distance from the surface of the reinforcing element 22 to the surface S4 or S5 of the vulcanized rubber-metal composite 21, which is T2a or T2b in Fig. 4. Usually, in order to check for uneven strength of the vulcanized rubber-metal composite 21, T2a and T2b are of the same length. If they are different, the layer thickness T2 is calculated as the average value of T2a and T2b. Hereinafter, the description will be made omitting the reference signs.

[0024] 〔Reinforcing Element〕 The reinforcing element is made of a metal filament, and the metal constituting the metal filament is steel whose surface is coated with a ternary plating of copper, zinc, and iron. The belt layer according to the present invention is formed by coating a reinforcing element made of a metal filament with crosslinked rubber. By adopting such a configuration, the adhesiveness between the steel cord and the crosslinked rubber is excellent.

[0025] The metal filament in the belt layer is preferably a substantially straight metal filament, but a metal filament shaped two-dimensionally such as a corrugated or zigzag shape may be used, or a three-dimensionally shaped one such as a spiral shape may be used. Here, the straight metal filament refers to a metal filament that has not been intentionally shaped and is substantially unshaped.

[0026] The steel cord may be either a steel monofilament or a multifilament (twisted cord or aligned bundle cord), and its shape is not limited. There is also no particular limitation on the twist structure when the steel cord is a twisted cord, and examples include single twist, double twist, layer twist, and composite twists such as double twist and layer twist. In addition, when there are a plurality of belt layers, the twist structures may be different or the same for each layer.

[0027] Furthermore, in the present invention, the wire diameter of the metal filament is preferably 0.15 mm or more and 0.40 mm or less. More preferably, it is 0.18 mm or more, still more preferably 0.20 mm or more, and preferably 0.35 mm or less. By setting the wire diameter of the metal filament to 0.40 mm or less, a weight reduction effect of the tire can be obtained, while by setting the wire diameter of the metal filament to 0.15 mm or more, sufficient belt strength can be exhibited. In addition, when there are a plurality of belt layers, either or both of the cord diameter and the filament diameter may be different or the same for each layer.

[0028] The thickness of the unvulcanized rubber covering the reinforcing element (layer thickness T1 of the unvulcanized rubber R1 covering the reinforcing element 22 in Fig. 3) is preferably 0.4 to 1.0 times the wire diameter of the reinforcing element, more preferably 0.5 to 0.8 times, and even more preferably 0.5 to 0.7 times, from the viewpoints of the strength, durability, and low fuel consumption of the retread tire.

[0029] The thickness of the vulcanized rubber covering the reinforcing element (layer thickness T2 of the vulcanized rubber R2 covering the reinforcing element 22 in Fig. 4) is preferably 0.4 to 1.0 mm, more preferably 0.5 to 0.8 mm, and even more preferably 0.5 to 0.7 mm, from the viewpoint of the balance of the strength, durability, and low fuel consumption of the tire.

[0030] In the present invention, the metal constituting the metal filament is steel (ternary-plated metal) whose surface is coated with ternary plating of copper, zinc, and iron. More specifically, in a steel cord containing one or more of the above steel filaments, the filament includes a steel filament base material and a coating (plating layer) that partially or entirely covers the steel filament base material. Since the steel cord has a ternary plating layer of copper, zinc, and iron, the components constituting the plating layer can play a role in enhancing the adhesiveness between the reinforcing element and the vulcanized rubber covering the reinforcing element. As a result, even when the content of the cobalt-containing compound in the rubber composition constituting the vulcanized rubber is small (0.01 part by mass or less with respect to 100 parts by mass of the rubber component), high adhesiveness between the reinforcing element and the vulcanized rubber can be achieved.

[0031] More preferably, the coating includes brass composed of copper and zinc, the coating is reinforced with iron, the iron exists as particles in the brass, and the particles have a size of 10 to 10,000 nanometers. Even more preferably, the particles have a size of 20 to 5,000 nanometers. "Reinforced with iron" means that the iron does not originate from the filamentous steel base material.

[0032] Here, the brass consists of copper and zinc, preferably contains at least 63% by mass of copper, with the remainder being zinc, more preferably contains 65% by mass or more of copper, and even more preferably contains 67% by mass or more of copper. Also, the amount of iron in the coating (plating layer) is preferably 1% or more and less than 10% by mass compared to the total mass of brass and iron, and more preferably the amount of iron in the coating is 3% or more and less than 9% by mass compared to the total mass of brass and iron. The steel cord is more preferably characterized in that the coating substantially does not contain a zinc-iron alloy.

[0033] From the viewpoint of suitably ensuring the adhesiveness with the rubber composition, the steel cord may further be subjected to surface treatment such as an adhesive treatment. When using an adhesive treatment, for example, an adhesive treatment such as the product name "Chemlock" (registered trademark) manufactured by LORD Corporation is preferable.

[0034] Also, in the present invention, the surface state of the metal filament is not particularly limited, but for example, it can take the following forms. That is, as the metal filament, a steel filament having 2 atomic% or more and 60 atomic% or less of N atoms on the surface and a Cu / Zn ratio on the surface of 1 or more and 4 or less can be used. Further, as the metal filament, there is a case where the amount of phosphorus contained as an oxide up to 5 nm from the outermost surface of the filament in the inward direction of the filament radius is 7.0 atomic% or less in the ratio of the total amount excluding the C amount.

[0035] In the steel cord containing one or more of the above steel filaments, the amount of phosphorus present on the surface of the filament, in other words, the amount of phosphorus in the coating (plating layer) is P s and the amount of iron present on the surface of the filament, in other words, the amount of iron in the coating (plating layer) is Fe s is, (P s + Fe sThe amount of

[0036] (a) Weigh about 5 grams of steel cord, cut it into fragments about 5 cm long, and introduce it into a test tube. (b) Add 10 ml of 0.01 mol hydrochloric acid HCl. (c) Shake the sample in the acid solution for 15 seconds. (d) Measure the amount present in the solution by ICP - OES. Here, ICP - OES refers to inductively coupled plasma - optical emission spectrometry (ICP - OES) that uses all of the standard solutions of (Cu; Fe; Zn) at (0; 0; 0), (2; 0.02; 1), (5; 0.1; 2), (10; 0.5; 5) mg / L in the matrix of a 10 - mL stripping solution. (e) The result showing the mass of (P s + Fe s ) per unit surface area of the filament in milligrams per square meter (mg / m 2 ) is shown. The result may be referred to as (Fe s + P s ).

[0037] The amount of phosphorus present on the surface of the filament, in other words, the amount of phosphorus in the coating (plating layer) is preferably more than 0 mg / m 2 and not more than 4 mg / m 2 . That is, 0 < P s ≤ 4 mg / m 2 . A larger amount of phosphorus P s reduces the growth of the adhesion layer. The amount of phosphorus P s may be lower than 3 mg / m 2 , and even better lower than 1.5 mg / m 2 .

[0038] In a more preferred embodiment, the amount of iron present on the surface of the filament is preferably 30 mg / m 2 or more, and 35 mg / m 2It is more preferable that iron exceeding [specific amount] exists on the surface, and even more preferably, iron exceeding 40 mg / m 2 exists on the surface. In addition, the mass ratio (Fe s / P s ) of the amount of iron present on the surface of the filament to the amount of phosphorus present on the surface of the filament is preferably greater than 27.

[0039] The surface coating mass SCW of the filament is the total mass of brass and iron present in the coating per unit of surface area, the coating mass is expressed in grams per square meter, and the mass ratio [Fe s / (SCW×P s )] is preferably greater than 13. As a method for obtaining the steel filament in which the iron exists as particles in the brass, an intermediate wire having a brass coating reinforced with iron particles may be continuously drawn through a smaller die in a lubricant by wet wire drawing until a final diameter of 0.28 mm is obtained to obtain the steel filament. The lubricant generally contains a high-pressure additive containing phosphorus in an organic compound. Here, as the die to be used, at least the head die is a sintered diamond die, and the remaining dies are tungsten carbide dies. A Set-D die may be used. The reinforcing element (steel cord) is preferably drawn by a diamond die.

[0040] 〔Crosslinked Rubber〕 The crosslinked rubber is a coating rubber that coats the reinforcing element and is obtained by crosslinking a rubber composition. The rubber composition is in an uncrosslinked state, and the rubber components contained in the rubber composition are also in an uncrosslinked state. In this specification, the rubber composition and the uncrosslinked rubber are synonymous, and the rubber composition constituting the crosslinked rubber means the uncrosslinked rubber. The rubber composition contains a rubber component, a filler, a crosslinking agent, etc.

[0041] (Rubber Component) As the rubber component, a diene-based rubber is usually used. Examples of the diene rubber include isoprene rubber, polybutadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), and the like, and modified rubbers thereof. Further, the rubber component may contain non-diene rubber as long as the effects of the present invention are not impaired. Only one kind of rubber component may be used, or two or more kinds may be mixed and used. Among these, from the viewpoint of further improving the adhesion between the crosslinked rubber and the reinforcing element, the rubber component preferably contains isoprene rubber.

[0042] Examples of the isoprene rubber include natural rubber (NR), polyisoprene rubber (IR), butadiene-isoprene copolymer rubber (BIR), styrene-isoprene copolymer rubber (SIR), styrene-butadiene-isoprene copolymer rubber (SBIR), and the like, and modified rubbers thereof. Only one kind of isoprene rubber may be used, or two or more kinds may be mixed and used. Among these, from the viewpoint of further improving the adhesion between the crosslinked rubber and the reinforcing element, the isoprene rubber is preferably one or more selected from the group consisting of natural rubber and polyisoprene rubber, and natural rubber is more preferable. As the natural rubber, epoxidized natural rubber, deproteinized natural rubber, and other modified natural rubbers may be used.

[0043] Examples of the natural rubber include natural rubbers of grades such as RSS#1, RSS#3, TSR20, and SIR20. As the epoxidized natural rubber, those having an epoxidation degree of 10 to 60 mol% are preferable, and examples thereof include ENR25 and ENR50 manufactured by Kumpulan Guthrie. As the deproteinized natural rubber, deproteinized natural rubber having a total nitrogen content of 0.3 mass% or less is preferable. As the other modified natural rubbers, modified natural rubbers containing polar groups obtained by reacting natural rubber in advance with N,N-dialkylaminoethyl acrylates such as 4-vinylpyridine and N,N-diethylaminoethyl acrylate, 2-hydroxyacrylate, etc. are used as needed.

[0044] The content of isoprene rubber in the rubber component is preferably more than 50% by mass, preferably 70% by mass or more, more preferably 90% by mass or more, and may be 100% by mass.

[0045] (Filler) By containing a filler in the rubber composition, the mechanical strength of the crosslinked rubber can be improved. The filler is preferably a reinforcing filler that reinforces the rubber composition. Examples of the reinforcing filler include carbon black; metal oxides such as silica, alumina, titania, and zirconia; metal carbonates such as magnesium carbonate and calcium carbonate; and aluminum hydroxide. Only one type of filler may be used, or two or more types may be used.

[0046] [Carbon Black] From the viewpoint of improving the reinforcing property of the crosslinked rubber and obtaining a belt layer excellent in adhesion between the crosslinked rubber and the reinforcing element, the filler preferably contains carbon black. The type of carbon black is not particularly limited and can be appropriately selected according to the purpose. The carbon black is preferably, for example, of FEF, SRF, HAF, ISAF, and SAF grades, more preferably of HAF, ISAF, and SAF grades, and still more preferably of HAF grade. Only one type of carbon black may be used, or two or more types may be used.

[0047] By using carbon black with a low dibutyl phthalate absorption amount (DBP absorption amount), that is, a low structure, the low-loss property of the vulcanized rubber can be improved. Also, from the viewpoint of improving the durability of the tire, the carbon black has a nitrogen adsorption specific surface area (N2SA) of 70 m 2 / g or more and 90 m 2 / g or less, and preferably has a dibutyl phthalate absorption amount (DBP absorption amount) of 50 mL / 100 g or more and 110 mL / 100 g or less.

[0048] From the viewpoint of further improving the adhesiveness between the crosslinked rubber and the reinforcing element, the nitrogen adsorption specific surface area of the carbon black is preferably 70 m 2 / g or more and 85 m 2 / g or less, more preferably 73 m 2 / g or more and 83 m 2 / g or less. Similarly, from the viewpoint of further improving the adhesiveness between the crosslinked rubber and the reinforcing element, the dibutyl phthalate absorption amount of the carbon black is more preferably 60 mL / 100 g or more and 110 mL / 100 g or less, and preferably 70 mL / 100 g or more and 110 mL / 100 g or less. In addition, since suppressing heat generation (loss) improves the adhesiveness between the crosslinked rubber and the reinforcing element, the grade of the carbon black is preferably a HAF grade (HAF, HAF-LS) with low heat generation (low loss). The carbon black may be used alone or in combination of two or more.

[0049] The N2SA of the carbon black is determined by Method A of JIS K 6217-2:2001 (Method for determining specific surface area - Nitrogen adsorption method - Single point method). The DBP absorption amount of the carbon black is measured by the method described in JIS K 6217-4:2001 "Method for determining DBP absorption amount" and is expressed in ml of the volume of dibutyl phthalate (DBP) absorbed per 100 g of the carbon black.

[0050] The content of the filler in the rubber composition is preferably 30 to 60 parts by mass with respect to 100 parts by mass of the rubber component. In particular, it is preferable that the rubber composition contains 35 to 60 parts by mass of carbon black with respect to 100 parts by mass of the rubber component. When the rubber composition contains 30 to 60 parts by mass of the filler with respect to 100 parts by mass of the rubber component, the reinforcing property of the crosslinked rubber is improved, and a belt layer excellent in the adhesiveness between the crosslinked rubber and the reinforcing element can be easily obtained.

[0051] (Silica) The filler may contain silica. The type of silica is not particularly limited, and examples include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), colloidal silica, etc. Silica may be used alone or in combination of two or more.

[0052] The cetyltrimethylammonium bromide (CTAB) specific surface area of silica is 80 m 2 / g or more and 250 m 2 / g or less, preferably 100 m 2 / g or more and 200 m 2 / g or less, more preferably 120 m 2 / g or more and 180 m 2 / g or less is even more preferable. When the CTAB specific surface area of silica is within the above range, the adhesiveness between the crosslinked rubber and the reinforcing element can be further improved. The CTAB specific surface area of silica can be measured by a method conforming to the method of ASTM-D3765-80. The rubber composition may further contain a silane coupling agent in order to improve the dispersibility of silica and also improve the reinforcing property and low heat build-up property of the crosslinked rubber.

[0053] From the viewpoints of improving the low loss property of the crosslinked rubber and the adhesiveness between the crosslinked rubber and the reinforcing element, and also from the viewpoint of the processability of the rubber composition, the content of silica in the rubber composition is preferably more than 0 parts by mass and 15 parts by mass or less with respect to 100 parts by mass of the rubber component. The content of silica in the rubber composition is more preferably 0.5 parts by mass or more and 12 parts by mass or less, and even more preferably 0.5 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the rubber component. From the viewpoint of the processability of the rubber composition, the content of silica in the rubber composition may be less than 5 parts by mass with respect to 100 parts by mass of the rubber component.

[0054] (Crosslinking agent) Examples of crosslinking agents include sulfur-based crosslinking agents, organic peroxide-based crosslinking agents, acid crosslinking agents, polyamine crosslinking agents, resin crosslinking agents, sulfur compound-based crosslinking agents, oxime-nitrosoamine-based crosslinking agents, and the like. Usually, one or more selected from the group consisting of sulfur-based crosslinking agents, sulfur compound-based crosslinking agents, etc., which are vulcanizing agents; and organic peroxide-based crosslinking agents are used. Note that crosslinked rubber crosslinked using a vulcanizing agent is called vulcanized rubber. Examples of organic peroxide-based crosslinking agents include diacyl peroxides, dialkyl peroxides, hydroperoxides, peroxoketals, alkyl peresters, percarbonates, ketone peroxides, and the like.

[0055] The content of the crosslinking agent in the rubber composition is preferably 0.1 to 10 parts by mass, more preferably 1 to 9 parts by mass, and even more preferably 2 to 8 parts by mass with respect to 100 parts by mass of the rubber component. By setting the content of the crosslinking agent within the above range, the adhesiveness between the crosslinked rubber and the reinforcing element is excellent, and the crosslinking time of the rubber composition is shortened.

[0056] [Vulcanization accelerator] When a vulcanizing agent is used as the crosslinking agent, the rubber composition preferably contains a vulcanization accelerator. Examples of vulcanization accelerators include thiazole-based vulcanization accelerators, thiuram-based vulcanization accelerators, sulfenamide-based vulcanization accelerators, and guanidine-based vulcanization accelerators described on pages 412 to 413 of the Rubber Industry Handbook <Fourth Edition> (published by the Japan Rubber Association, a corporate body, on January 20, Heisei 6).

[0057] Examples of thiuram-based vulcanization accelerators include tetrakis(2-ethylhexyl)thiuram disulfide, tetraethylthiuram disulfide, tetramethylthiuram disulfide, tetrabutylthiuram disulfide, tetramethylthiuram monosulfide, dipentamethylene thiuram tetrasulfide, tetrabenzylthiuram disulfide, and the like. Thiuram vulcanization accelerators may be commercially available products. For example, as tetra kis(2-ethylhexyl)thiuram disulfide, there is "Nocceler TOT" manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.; as tetraethylthiuram disulfide, there is "Nocceler TET" manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.; as tetramethylthiuram disulfide, there is "Nocceler TT" manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.; as tetrabutylthiuram disulfide, there is "Nocceler TBT" manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.; as tetramethylthiuram monosulfide, there is "Nocceler TS" manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.; as dipentamethylene thiuram tetrasulfide, there is "Nocceler TRA" manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.; as tetrabenzylthiuram disulfide, there is "Accel TBzTD" manufactured by Kawaguchi Chemical Industry Co., Ltd., etc.

[0058] Examples of sulfenamide vulcanization accelerators include N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N,N-dicyclohexyl-2-benzothiazolylsulfenamide, N-tert-butyl-2-benzothiazolylsulfenamide (BBS), N-oxydiethylene-2-benzothiazolylsulfenamide, N-methyl-2-benzothiazolylsulfenamide, N-ethyl-2-benzothiazolylsulfenamide, N-propyl-2-benzothiazolylsulfenamide, N-butyl-2-benzothiazolylsulfenamide, N-pentyl-2-benzothiazolylsulfenamide, N-hexyl-2-benzothiazolylsulfenamide, N-heptyl-2-benzothiazolylsulfenamide, N-octyl-2-benzothiazolylsulfenamide, N-2-ethylhexyl-2-benzothiazolylsulfenamide, N-decyl-2-benzothiazolylsulfenamide, N-dodecyl-2-benzothiazolylsulfenamide, N-stearyl-2-benzothiazolylsulfenamide, N,N-dimethyl-2-benzothiazolylsulfenamide, N,N-diethyl-2-benzothiazolylsulfenamide, N,N-dipropyl-2-benzothiazolylsulfenamide, N,N-dibutyl-2-benzothiazolylsulfenamide, N,N-dipentyl-2-benzothiazolylsulfenamide, N,N-dihexyl-2-benzothiazolylsulfenamide, N,N-diheptyl-2-benzothiazolylsulfenamide, N,N-dioctyl-2-benzothiazolylsulfenamide, N,N-di-2-ethylhexylbenzothiazolylsulfenamide, N,N-didecyl-2-benzothiazolylsulfenamide, N,N-didodecyl-2-benzothiazolylsulfenamide, N,N-distearyl-2-benzothiazolylsulfenamide, and the like.

[0059] Sulfenamide vulcanization accelerators may be commercially available products. For example, as N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), there is "Nocceler CZ" manufactured by Ouchi Shinko Chemical Industry Co., Ltd.; as N-tert-butyl-2-benzothiazolylsulfenamide (BBS), there is "Nocceler NS" manufactured by Ouchi Shinko Chemical Industry Co., Ltd.; as N-oxydiethylene-2-benzothiazolylsulfenamide, there is "Nocceler MSA" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. or "Accel NS" manufactured by Kawaguchi Chemical Industry Co., Ltd., etc.

[0060] Examples of thiazole vulcanization accelerators include 2-mercaptobenzothiazole (MBT), dibenzothiazyl disulfide (MBTS), etc. Examples of guanidine vulcanization accelerators include diphenylguanidine (DPG), 1,3-di-o-tolylguanidine (DOTG), 1-o-tolylbiguanide (OTBG), etc. In addition, vulcanization accelerators such as thiourea vulcanization accelerators like trimethylthiourea (TMU), N,N'-diethylthiourea (DEU), N,N'-diphenylthiourea, etc. may be used.

[0061] The amount of the vulcanization accelerator used is not particularly limited, but a range of 0.5 parts by mass or more and 10 parts by mass or less, more preferably 0.5 parts by mass or more and 8 parts by mass or less, still more preferably 0.5 parts by mass or more and 7 parts by mass or less, and particularly preferably 0.5 parts by mass or more and 6 parts by mass or less, is preferred with respect to 100 parts by mass of the rubber component.

[0062] (Cobalt-containing compound) In the rubber composition, the content of the cobalt-containing compound is preferably 0.01 parts by mass or less with respect to 100 parts by mass of the rubber component. This means that the rubber composition substantially does not contain a cobalt-containing compound. Examples of the cobalt-containing compound include cobalt organic acid salts, cobalt metal complexes, etc. Examples of cobalt organic acid salts include cobalt naphthenate, cobalt stearate, cobalt neodecanoate, cobalt rosinate, cobalt versatate, cobalt tallate, cobalt oleate, cobalt linoleate, cobalt linolenate, cobalt palmitate, and the like. Examples of cobalt metal complexes include cobalt acetylacetonate. The rubber composition preferably does not contain a cobalt-containing compound, that is, the content of the cobalt-containing compound in the rubber composition is 0.00 parts by mass with respect to 100 parts by mass of the rubber component.

[0063] Conventionally, a cobalt-containing compound has been used to obtain the effect of adhesion between crosslinked rubber and metal. However, by using a metal in which the surface of a steel cord is coated with a ternary plating of copper, zinc, and iron as the metal constituting the metal filament, the rubber composition has excellent adhesion between the crosslinked rubber and the reinforcing element even if it does not contain a cobalt-containing compound. In addition, since the rubber composition does not contain a cobalt-containing compound, metal corrosion can be suppressed and the environmental burden can be reduced.

[0064] (Various components) The rubber composition may contain various chemicals usually used in the rubber industry, such as crosslinking retarders (vulcanization retarders), process oils, anti-aging agents, resins, zinc oxide, stearic acid, etc., as long as the effects of the present invention are not impaired.

[0065] [Anti-aging agent] Examples of anti-aging agents include those described on pages 436 to 443 of "Rubber Industry Handbook <Fourth Edition>" edited by the Japan Rubber Association. Specifically, for example, amine-based, quinoline-based, quinone-based, phenol-based, imidazole-based compounds, and anti-aging agents such as metal carbamates can be mentioned.

[0066] Examples of amine-based anti-aging agents include phenylenediamine-based anti-aging agents having a phenylenediamine skeleton (-NH-Ph-NH-). Specifically, for example, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (sometimes referred to as 6PPD or 6C), N-isopropyl-N'-phenyl-p-phenylenediamine (sometimes referred to as 3C), N,N'-diphenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, N-cyclohexyl-N'-phenyl-p-phenylenediamine, N,N'-bis(1-methylheptyl)-p-phenylenediamine, N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine, N,N'-dicyclohexyl-p-phenylenediamine, N,N'-bis(1-ethyl-3-methylpentyl)-p-phenylenediamine, N-4-methyl-2-pentyl-N'-phenyl-p-phenylenediamine, N,N'-diaryl-p-phenylenediamine, hindered diaryl-p-phenylenediamine, phenylhexyl-p-phenylenediamine, phenyloctyl-p-phenylenediamine, etc. can be mentioned.

[0067] Among them, it is preferable that there is no double bond except for the phenylenediamine moiety (-NH-Ph-NH-), and specifically, the amine-based antioxidant represented by the following formula (1) (R 1 -NH-Ph-NH-R 2 ) is preferable.

[0068]

Chemical formula

[0069] In the above formula (1), R 1 and R 2 are each independently a monovalent saturated hydrocarbon group. R 1 and R 2 may be the same or different, but from the viewpoint of synthesis, it is preferably the same.

[0070] The number of carbon atoms of the monovalent saturated hydrocarbon group is preferably 1 to 20, more preferably 3 to 10, and particularly preferably 6 and 7. When the number of carbon atoms of the saturated hydrocarbon group is 20 or less, the number of moles per unit mass increases, so the anti-aging effect increases, and the ozone resistance of the vulcanized rubber of the rubber composition is improved. R in the above formula (1) 1 and R 2 are each independently preferably a linear monovalent saturated hydrocarbon group having 1 to 20 carbon atoms or a cyclic monovalent saturated hydrocarbon group having 5 to 20 carbon atoms from the viewpoint of further improving the ozone resistance of the vulcanized rubber of the rubber composition.

[0071] Examples of the monovalent saturated hydrocarbon group include an alkyl group and a cycloalkyl group. The alkyl group may be linear or branched, and the cycloalkyl group may further have an alkyl group or the like bonded thereto as a substituent. Examples of the alkyl group include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, 1,2-dimethylbutyl group, 1,3-dimethylbutyl group, 2,3-dimethylbutyl group, n-pentyl group, isopentyl group, neopentyl group, 1-methylpentyl group, 2-methylpentyl group, 3-methylpentyl group, 4-methylpentyl group, 1,2-dimethylpentyl group, 1,3-dimethylpentyl group, 1,4-dimethylpentyl group, 2,3-dimethylpentyl group, 2,4-dimethylpentyl group, 3,4-dimethylpentyl group, n-hexyl group, 1-methylhexyl group, 2-methylhexyl group, various octyl groups, various decyl groups, various dodecyl groups, etc. Among these, 1,4-dimethylpentyl group is preferred. Examples of the cycloalkyl group include cyclopentyl group, methylcyclopentyl group, cyclohexyl group, methylcyclohexyl group, cycloheptyl group, cyclooctyl group, etc. Among these, cyclohexyl group is preferred.

[0072] The amine-based antioxidant represented by formula (1) may be supported on any carrier. For example, the amine-based antioxidant represented by formula (1) may be supported on an inorganic filler such as silica or calcium carbonate. In addition, the amine-based antioxidant represented by formula (1) may form a masterbatch together with the rubber component. Here, the rubber component used when making a masterbatch is not particularly limited, and may be a diene rubber such as natural rubber (NR), or may be ethylene-propylene-diene rubber (EPDM) or the like. Further, the amine-based antioxidant represented by formula (1) may be in the form of a salt with an organic acid. Here, the organic acid used when making a salt is not particularly limited, and examples include stearic acid.

[0073] In addition, quinoline-based antioxidants can also be preferably used. Examples of quinoline-based antioxidants include 2,2,4-trimethyl-1,2-dihydroquinoline polymer (sometimes referred to as RD or 224), 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline (sometimes referred to as AW), and the like. In addition, a high-temperature condensate of diphenylamine and acetone may be used. The above antioxidants may be used alone or in combination of two or more. Among the above, the antioxidant preferably contains one or more selected from the group consisting of amine-based antioxidants and quinoline-based antioxidants, and more preferably contains at least an amine-based antioxidant.

[0074] The amount of the antioxidant used is preferably 0.1 to 8.0 parts by mass, more preferably 0.1 to 6.0 parts by mass, and particularly preferably 0.3 to 5.0 parts by mass with respect to 100 parts by mass of the rubber component.

[0075] [Resin] Examples of the resin include C5-based resins, C5 / C9-based resins, C9-based resins, phenolic resins, terpene-based resins, terpene-aromatic compound-based resins, etc. These resins may be used alone or in combination of two or more.

[0076] (Preparation of Rubber Composition) The rubber composition is obtained by kneading the above-described various components and additives using a kneader such as an open kneader like a roll or a closed kneader like a Banbury mixer.

[0077] [Recycled Rubber, Truck Tire Rubber] Recycled rubber is also a crosslinked rubber formed by crosslinking a rubber composition, and the rubber constituting a truck tire is also a crosslinked rubber formed by crosslinking a rubber composition. The rubber composition serving as a raw material for the coating rubber of the reinforcing element, the rubber composition serving as a raw material for recycled rubber (rubber composition for recycled rubber), and the rubber composition serving as a raw material for the rubber constituting a truck tire (rubber composition for truck tire rubber) may be the same or different.

[0078] Note that recycled rubber may be manufactured by crosslinking after molding using an uncrosslinked rubber composition according to the type of recycled tire to be applied, or may be manufactured by further performing final crosslinking after molding using a semi-crosslinked rubber that has undergone a preliminary crosslinking process or the like.

[0079] The recycled tire of the present invention preferably has a cobalt atom content of 1% by mass or less. The cobalt atom content in the recycled tire can be said to be 0% by mass if the rubber composition used for tire manufacturing does not contain a cobalt-containing compound and the metal constituting the metal filament does not contain cobalt. The cobalt atom content in the recycled tire can be measured, for example, by a method of measuring the elemental amounts of each member constituting the tire.

Examples

[0080] [Examples 1 to 2 and Comparative Examples 1 to 2] [Preparation of Rubber Composition] According to the formulation shown in Table 1, a rubber composition is prepared using a normal Banbury mixer. The blending amount of each component in Table 1 is the amount (parts by mass) relative to 100 parts by mass of the rubber component. The details of each component in Table 1 are as follows. The rubber composition is used not only for coating rubber of steel cords but also for manufacturing a case part, a precure tread member, and an uncured rubber sheet for adhering a tubeless tire and the precure tread member.

[0081] (1) Natural rubber: TSR10 (2) Carbon black: HAF grade carbon black, manufactured by Asahi Carbon Co., Ltd., trade name "Asahi #70L" (nitrogen adsorption specific surface area = 81 m 2 / g) (3) Cobalt organic acid salt: manufactured by OMG Co., Ltd., trade name "Manobond C" (4) Zinc white: manufactured by Hakusuitec Co., Ltd., trade name "Zinc Oxide Type 2" (5) Stearic acid: manufactured by Shin Nippon Rika Co., Ltd., trade name "Stearic Acid 50S" (6) Antioxidant 1: 2,2'-methylenebis(4-methyl-6-tert-butylphenol), manufactured by Ouchi Shinko Chemical Industrial Co., Ltd., trade name "No Crack NS-6" (7) Antioxidant 2: N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine, manufactured by Ouchi Shinko Chemical Industrial Co., Ltd., trade name "No Crack 6C" (8) Antioxidant 3: manufactured by Seiko Chemical Co., Ltd., trade name "Nonflex RD-S" (9) Crosslinking agent: sulfur, manufactured by Tsurumi Chemical Industry Co., Ltd., trade name "Powder Sulfur" (10) BMI: N,N'-(4,4'-diphenylmethane)bismaleimide, manufactured by Yamato Kasei Kogyo Co., Ltd., trade name "BMI-RB" (11) Alkylphenol resin: alkylphenol formaldehyde resin, manufactured by SUMITOMO BAKELITE EUROPE Co., Ltd., trade name "DUREZ 19900" *(12) Vulcanization accelerator 1: sulfenamide-based vulcanization accelerator, N,N-dicyclohexyl benzothiazyl-2-sulfenamide, manufactured by Ouchi Shinko Chemical Industrial Co., Ltd., trade name "Nocceler DZ" (13) Vulcanization accelerator 2: sulfenamide-based vulcanization accelerator, N-cyclohexyl-2-benzothiazolylsulfenamide, manufactured by Ouchi Shinko Chemical Industrial Co., Ltd., trade name "Nocceler CZ-G"

[0082] [Preparation of Uncured Rubber-Metal Composite] (Examples 1-2) A steel cord with a surface coated with a ternary plating of copper, zinc, and iron and containing about 4% by mass of iron can be used as the metal. This ternary-plated steel cord is obtained using a Set-D die, and more specifically, is manufactured by the method described in paragraphs

[0065] to

[0070] of International Publication No. 2020 / 156967. The ternary-plated steel cord is coated from both the upper and lower sides with a sheet having the thickness shown in the "Coated Rubber Thickness" column of Table 1 made of the prepared rubber composition, and an unvulcanized rubber-metal composite 1 (unvulcanized steel cord topping reaction) for use in the belt layer is produced.

[0083] (Comparative Examples 1-2) An unvulcanized rubber-metal composite 101 is produced in the same manner as in Example 1, except that a steel cord with a surface coated with brass brass plating (Cu: 63% by mass, Zn: 37% by mass) is used as the metal of the vulcanized rubber-metal composite.

[0084] Here, in Table 1, plating types A and B are as follows. A: Ternary plating of copper, zinc, and iron (containing about 4% by mass of iron) B: Brass plating of brass (Cu: 63% by mass, Zn: 37% by mass)

[0085] <Manufacture of Retread Tires> Retread tires are manufactured as follows. An unvulcanized rubber-metal composite 1 or an unvulcanized rubber-metal composite 101 is applied to the outermost belt layer, and a case part provided with a belt composed of 4 belt layers with the innermost belt layer being a cross ply is prepared. The case part is surrounded from the outside by a vulcanization mold and vulcanized by a method of pressurizing and heating with a vulcanization bladder from the inside (pressurizing with high-pressure steam at 150°C) to manufacture a casing tire. Separately, a precure tread member (retread rubber) heated and vulcanization molded at 160°C so as to pre-mold a tread pattern in advance is prepared.

[0086] The adhesion surface between the casing tire and the precure tread member is polished with a buffing machine. Next, an unvulcanized rubber sheet for adhering the casing tire and the precure tread member is first attached to the casing tire, and then the precure tread member is attached to the casing tire. Thereafter, vulcanization is carried out at 120° C. for 2 hours using a vulcanizing device (vulcanizing autoclave) to obtain a retread tire in which the casing tire and the precure tread member are adhered.

[0087] <Evaluation> 1. Durability In Example 1 and Comparative Example 1, the manufactured retread tire is mounted on the rim of a wheel, and this is attached to a drum tester to conduct a drum running test of 100,000 km. In Example 2 and Comparative Example 2, the manufactured retread tire is mounted on the rim of a wheel, and this is attached to a drum tester to conduct a drum running test of 100,000 km. Thereafter, buffing or the like is performed on the main part worn by running to remove unnecessary substances, the precure tread member is attached to the casing tire to obtain a retread tire. Further, a drum running test of 100,000 km is conducted.

[0088] In Example 1 and Comparative Example 1, after running 100,000 km, and in Example 2 and Comparative Example 2, after running 200,000 km, a vulcanized rubber-metal composite is cut out from the retread tire in dimensions of 5 cm in width × 20 cm in length centered on the crown center. Steel cords are pulled out from the vulcanized rubber-metal composite. The coating state of the vulcanized rubber adhering to the steel cords is observed visually, and the vulcanized rubber adhesion amounts of Examples 1 to 2 and Comparative Example 2 with respect to the vulcanized rubber adhesion amount (adhesion area) of Comparative Example 1 are calculated. Based on the calculated vulcanized rubber adhesion amounts, the durability of the retread tire is evaluated according to the following evaluation criteria. It can be said that the higher the vulcanized rubber adhesion amount, the more excellent the durability of the retread tire (especially the casing tire). ◎: Compared with the vulcanized rubber adhesion amount of Comparative Example 1, the vulcanized rubber adhesion amount is 95% or more ○: Compared with the vulcanized rubber adhesion amount of Comparative Example 1, the vulcanized rubber adhesion amount is 90% or more and less than 95% △: Compared with the vulcanized rubber adhesion amount of Comparative Example 1, the vulcanized rubber adhesion amount is 80% or more and less than 90% ×: Compared with the vulcanized rubber adhesion amount of Comparative Example 1, the vulcanized rubber adhesion amount is less than 80%

[0089] 2. Environmental properties The environmental properties were evaluated based on whether a cobalt-containing compound was compounded in the rubber composition used for manufacturing the rubber coating of the steel cord. ○: No cobalt-containing compound is compounded in the rubber composition. ×: A cobalt-containing compound is compounded in the rubber composition.

[0090]

Table 1

[0091] It can be seen that the retreaded tires of Examples 1 to 2 not only showed excellent durability after running 100,000 km, but also after being retreaded once and then running another 100,000 km, as the vulcanized rubber-metal adhesion did not decrease. Furthermore, since the steel cord and the coating rubber do not contain cobalt, the environmental load is suppressed.

Industrial applicability

[0092] The retreaded tire of the present invention is excellent in the adhesion between the steel cord and its coating crosslinked rubber, and thus is suitably used as a heavy-duty tire such as a truck / bus tire, a large tire, an aircraft tire, etc.

Explanation of reference numerals

[0093] 1: Retreaded tire 2: Bead core 3: Stiffener 4: Carcass 5: Belt (5d: Outermost belt layer) 6: Belt wedge rubber 7: Cushion rubber layer 8: Retreaded rubber (tread) 9: Sidewall rubber 10: Inner liner 20: Uncrosslinked rubber-metal composite 21: Crosslinked rubber-metal composite 22: Reinforcing element A: Taiwan tire B: Pre-cure tread member M: Side N: Bead

Claims

1. In a retread tire having a carcass and a belt from the inner side in the tire radial direction and a retread rubber disposed on the outer side in the tire radial direction of the base tire, the belt layer at the outermost layer in the tire radial direction includes a reinforcing element made of a metal filament and a crosslinked rubber covering the reinforcing element, and the metal constituting the metal filament is steel whose surface is coated with a ternary plating of copper, zinc, and iron, and the retread tire is in the crosslinked rubber-metal composite covering the reinforcing element, the thickness of the crosslinked rubber covering the reinforcing element, which is the shortest distance from the surface of the reinforcing element to the surface of the crosslinked rubber-metal composite, is 0.4 to 1.0 mm. A retread tire.

2. The retread tire according to claim 1, wherein the amount of iron in the coating is 1% by mass or more and less than 10% by mass of the total mass of the copper, the zinc, and the iron.

3. The amount of phosphorus in the coating is more than 0 mg / m ２ and not more than 4 mg / m ２ The retread tire according to claim 1 or 2, wherein the amount is as described above.

4. The retread tire according to any one of claims 1 to 3, wherein the reinforcing element is drawn by a diamond die.

5. In the cross section of the uncrosslinked rubber-metal composite covering the reinforcing element, the thickness of the crosslinked rubber covering the reinforcing element, which is the shortest distance from the center of the reinforcing element to the surface of the uncrosslinked rubber-metal composite, when the crosslinked rubber is not crosslinked, is 0.4 to 1.0 times the wire diameter of the reinforcing element. The retread tire according to any one of claims 1 to 4.

6. The retread tire according to any one of claims 1 to 5, wherein the content of the cobalt-containing compound in the rubber composition constituting the crosslinked rubber is 0.01% by mass or less.

7. The retread tire according to any one of claims 1 to 6, wherein the content of cobalt atoms is 1% by mass or less.

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