Pneumatic tire, and pneumatic tire manufacturing method

Abstract

To provide a pneumatic tire of which durability is improved and weight saving can be achieved.SOLUTION: In a pneumatic tire 10, a carcass ply 1 of one or more layers, in which cut cords are arranged in parallel, is toroidally arranged, and one or more belt layers 2, in which the cut cords are arranged in parallel, are arranged on a tire radial direction outer side of a crown part of the carcass ply 1. In the pneumatic tire 10, an auxiliary reinforcement layer 4 containing a copolymer having a conjugated diene unit and a non-conjugated olefin unit is arranged adjacent to the vicinity of a cord cut end of at least one layer of the carcass ply 1 and the belt layer 2 or the vicinity a tire width direction outer side end of a chafer located outside the carcass ply 1 in a bead part 5.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a pneumatic tire and a method for manufacturing a pneumatic tire. [Background technology]

[0002] Typically, cord materials constituting the belt layers and carcass plies of pneumatic tires are subjected to an adhesive treatment to bond them to rubber. However, because the belt layers and carcass plies are cut to the desired dimensions after component manufacturing, the cut ends expose the cross sections of the cords without any surface coating for adhesion. Such cut ends of the cords that are not bonded to the rubber are prone to becoming the starting point for cracks due to strain input during running. Therefore, in tires including cord reinforcing layers such as carcass plies and belt layers, various technologies have been investigated to prevent cracks from propagating from the cut ends of the cords in the cord reinforcing layers, such as the turned-up ends of the carcass ply and the widthwise ends of the belt layers, thereby improving tire durability.

[0003] The propagation of cracks from the cut cord ends is due to the following mechanism: At the turned-up end of the carcass ply in the bead portion, a force acts in the direction that pulls out the carcass ply when the tire is pressurized, while at the same time, when the tire is rolling under load, the bead portion is bent, causing repeated tensile and compressive deformation in the radial direction of the tire, which causes cracks in the rubber due to the difference in rigidity between the turned-up end and the surrounding rubber. Similarly, at the ends of the belt layers, deformation during internal pressure application and rolling under load also causes cracks in the rubber due to the difference in rigidity between the turned-up end and the surrounding rubber.

[0004] In response to this, Patent Document 1 below proposes a technique in which an auxiliary reinforcing layer is provided adjacent to the vicinity of the cord cut end of the cord reinforcing layer. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-135019 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when an auxiliary reinforcing layer is disposed near the cut cord end of the cord reinforcing layer as in the technology described in Patent Document 1, the weight of the auxiliary reinforcing layer increases the weight of the tire, resulting in a problem of worsening fuel efficiency of the tire.

[0007] Therefore, an object of the present invention is to solve the above-mentioned problems of the conventional technology and to provide a pneumatic tire that can improve durability by suppressing the propagation of cracks from the cut ends of the cords in the cord reinforcement layer, while also achieving weight reduction. Another object of the present invention is to provide a method for manufacturing such a pneumatic tire. [Means for solving the problem]

[0008] The pneumatic tire and the method for manufacturing a pneumatic tire according to the present invention, which solve the above problems, are outlined as follows.

[0009] [1] A pneumatic tire in which one or more carcass plies, each having cut cords arranged in parallel, are wound around a bead core at their side portions to form a toroidal shape, and one or more belt layers, each having cut cords arranged in parallel, are arranged on the radially outer side of the crown portion of the carcass ply, An auxiliary reinforcing layer is disposed adjacent to the vicinity of a cut end of a cord of at least one of the carcass ply and the belt layer as a main cord reinforcing layer, or adjacent to the vicinity of an outer end in the tire width direction of a chafer disposed on the outer side of the carcass ply in a bead portion, and the auxiliary reinforcing layer is disposed at a position covering at least the cut end of the cord of the adjacent main cord reinforcing layer or the vicinity of the outer end in the tire width direction of the chafer from the inner side and / or the outer side of the tire, A pneumatic tire, wherein the auxiliary reinforcing layer contains a copolymer having conjugated diene units and non-conjugated olefin units. The pneumatic tire of the present invention described in [1] above has improved durability and can also be made lighter.

[0010] [2] The pneumatic tire according to [1], wherein the copolymer has a melting point of 50 to 120°C. In the pneumatic tire described in [2] above, the auxiliary reinforcing layer containing the copolymer has high crack resistance, and the workability in manufacturing the auxiliary reinforcing layer containing the copolymer is improved.

[0011] [3] The pneumatic tire according to [1] or [2], wherein the copolymer has a content of the conjugated diene units of more than 0 mol% and not more than 50 mol%, and a content of the non-conjugated olefin units of 50 mol% or more and less than 100 mol%. According to the pneumatic tire described in the above item [3], the high temperature fracture properties of the auxiliary reinforcing layer containing the copolymer can be effectively improved.

[0012] [4] The pneumatic tire according to any one of [1] to [3], wherein the copolymer further contains an aromatic vinyl unit. According to the pneumatic tire described in the above item [4], the crack resistance of the auxiliary reinforcing layer containing the copolymer can be improved.

[0013] [5] A first belt layer arranged on the radially outer side of the crown portion of the carcass ply and having cut cords arranged in parallel; a second belt layer disposed radially outward of the first belt layer and including cut cords arranged in parallel, The first belt layer and the second belt layer are each formed by embedding a plurality of cords in a coating rubber, The thickness of the first belt layer and the thickness of the second belt layer in a tire center portion are both 1.00 mm or less, where a is the shortest distance between a cord of the second belt layer and a cord of the first belt layer in the tire center portion, and b is the shortest distance between a cord at an end of the second belt layer and a cord of the first belt layer, b / a is 1.8 or more and 4.0 or less, the auxiliary reinforcing layer is disposed at the end portions of the first belt layer and the second belt layer, on the inner side in the tire radial direction of the first belt layer, between the first belt layer and the second belt layer, and on the outer side in the tire radial direction of the second belt layer; The pneumatic tire according to any one of [1] to [4], wherein when a portion of the auxiliary reinforcing layer located inside the first belt layer in the tire radial direction is defined as auxiliary reinforcing portion A, a portion of the auxiliary reinforcing layer located between the first belt layer and the second belt layer is defined as auxiliary reinforcing portion B, and a portion of the auxiliary reinforcing layer located outside the second belt layer in the tire radial direction is defined as auxiliary reinforcing portion C, auxiliary reinforcing portion B has the longest length in the direction toward the center portion and is closest to the tire center portion. According to the pneumatic tire described in the above item [5], the durability of the belt end portion can be improved.

[0014] [6] The lengths of the auxiliary reinforcing portions A, B, and C in the direction toward the tire center are respectively defined as L A , L B and L C When L A / L B is 0.5 or less, and L C / L B The pneumatic tire according to [5], wherein the value is 0.5 or less. According to the pneumatic tire described in [6] above, the formation of gaps at the belt ends can be further suppressed.

[0015] [7] The pneumatic tire according to [5] or [6], wherein the distance between the interface and the cord of the first belt layer and the distance between the interface and the cord of the second belt layer in the tire center portion are both 0.14 mm or less. According to the pneumatic tire described in [7] above, it is possible to more sufficiently improve low rolling resistance.

[0016] [8] The pneumatic tire according to any one of [1] to [7], wherein the auxiliary reinforcing layer is disposed in the vicinity of a cut end of the cord of at least one of the belt layers. According to the pneumatic tire described in [8] above, it is possible to effectively suppress the occurrence of cracks from the cut ends of the cords of the belt layers, and also to achieve a reduction in weight.

[0017] [9] A method for manufacturing a pneumatic tire according to any one of [1] to [8], a sheet-making step of making a sheet comprising a copolymer having conjugated diene units and non-conjugated olefin units; a cutting step of cutting the obtained sheet into strips; an attachment step of attaching the strip obtained in the primary molding of the green tire adjacent to the vicinity of the cord cut ends of the carcass ply, which is the carcass folded-up portion of the cylindrical molded body of the carcass ply, so as to cover at least the cord cut ends from the outer side of the tire over the entire circumference; and an expansion step of expanding the strip together with the carcass ply to a predetermined outer diameter in secondary molding of the green tire. According to the method for manufacturing a pneumatic tire described in [9] above, it is possible to obtain a pneumatic tire that has improved durability and is also lightweight.

[0018]

[10] In the sheet preparation step, a sheet having a thickness of 0.07 to 5 mm (for example, 0.07 to 1.5 mm) is prepared, The method for producing a pneumatic tire according to [9], wherein in the cutting step, the obtained sheet is cut at intervals of 20 to 1000 mm. According to the method for manufacturing a pneumatic tire described in

[10] above, it is easy to form an auxiliary reinforcing layer having a desired shape and thickness.

[0019]

[11] A method for manufacturing a pneumatic tire according to any one of [5] to [7], a lamination step of laminating the first belt layer and the second belt layer, a method for manufacturing a pneumatic tire, characterized in that, prior to the lamination step, an end portion of the first belt layer is wrapped with a first sheet containing a copolymer having a conjugated diene unit and a non-conjugated olefin unit, and an end portion of the second belt layer is wrapped with a second sheet containing a copolymer having a conjugated diene unit and a non-conjugated olefin unit, and at that time, for both the first sheet and the second sheet, the end portions of the belt layers are wrapped with a shift so that the length of the sheet portion located on the side facing the other belt layer when laminated is longer than the length of the sheet portion located on the opposite side. According to the method for manufacturing a pneumatic tire described in

[11] above, it is possible to effectively prevent gaps from being formed between the first belt layer and the second belt layer, and between the second belt layer and a layer that may be arranged outside the second belt layer (for example, a belt reinforcing layer).

[0020]

[12] The method for manufacturing a pneumatic tire according to

[11] , wherein, when the first belt layer and the second belt layer are laminated together, an end of the first sheet located between the first belt layer and the second belt layer does not overlap with an end of the second sheet. According to the method for manufacturing a pneumatic tire described in

[12] above, it is possible to further suppress the formation of gaps at the belt ends. [Effects of the Invention]

[0021] According to the present invention, it is possible to provide a pneumatic tire that has improved durability and can also be made lighter. Furthermore, according to the present invention, it is possible to provide a method for manufacturing a pneumatic tire that has improved durability and can also achieve weight reduction. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a cross-sectional view of one side in the width direction showing an example of a pneumatic tire of the present invention. [Figure 2]FIG. 2 is a partial cross-sectional view in the width direction showing another example of a pneumatic tire of the present invention. [Figure 3] FIG. 3 is a partial cross-sectional view in the width direction showing still another example of a pneumatic tire of the present invention. [Figure 4] FIG. 3 is a partial cross-sectional view in the width direction showing still another example of a pneumatic tire of the present invention. [Figure 5] FIG. 3 is a partial cross-sectional view in the width direction showing still another example of a pneumatic tire of the present invention. [Figure 6] FIG. 3 is a partial cross-sectional view in the width direction showing still another example of a pneumatic tire of the present invention. [Figure 7] FIG. 3 is a partial cross-sectional view in the width direction showing still another example of a pneumatic tire of the present invention. [Figure 8] FIG. 3 is a partial cross-sectional view in the width direction showing still another example of a pneumatic tire of the present invention. [Figure 9] FIG. 3 is a partial cross-sectional view in the width direction showing still another example of a pneumatic tire of the present invention. [Figure 10] FIG. 3 is a cross-sectional view of one side in the width direction showing yet another example of a pneumatic tire of the present invention. [Figure 11] FIG. 3 is a partial cross-sectional view in the width direction showing still another example of a pneumatic tire of the present invention. [Figure 12] FIG. 3 is a partial cross-sectional view in the width direction showing still another example of a pneumatic tire of the present invention. [Figure 13] FIG. 3 is a partial cross-sectional view in the width direction showing still another example of a pneumatic tire of the present invention. [Figure 14] FIG. 3 is a partial cross-sectional view in the width direction showing still another example of a pneumatic tire of the present invention. [Figure 15] FIG. 3 is a partial cross-sectional view in the width direction showing still another example of a pneumatic tire of the present invention. [Figure 16] 1 is a schematic half-sectional view of a pneumatic tire according to one embodiment of the present invention. [Figure 17A] 2 is a schematic cross-sectional view of an end portion of a belt in a pneumatic tire according to one embodiment of the present invention. FIG. [Figure 17B] FIG. 4 is a schematic cross-sectional view of an end portion of a belt in a pneumatic tire according to another embodiment of the present invention. [Figure 18]2 is a schematic cross-sectional view of a tire center portion and an end portion of a belt in a pneumatic tire according to one embodiment of the present invention. FIG. [Figure 19] 1 is a schematic cross-sectional view of a tire center portion of a belt in a pneumatic tire according to one embodiment of the present invention. [Figure 20A] 1 is a schematic diagram illustrating a part of a method for manufacturing a pneumatic tire according to an embodiment of the present invention. [Figure 20B] FIG. 20B is a schematic cross-sectional view of an end portion of a belt in a pneumatic tire obtained according to the manufacturing method of FIG. 20A. [Figure 21A] 4 is a schematic diagram showing a part of a manufacturing method of a comparative pneumatic tire. FIG. [Figure 21B] FIG. 21B is a schematic cross-sectional view of an end portion of a belt in a pneumatic tire obtained according to the manufacturing method of FIG. 21A. DETAILED DESCRIPTION OF THE INVENTION

[0023] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A pneumatic tire and a method for manufacturing a pneumatic tire according to the present invention will be described in detail below by way of example based on embodiments thereof.

[0024] <Definition> The compounds described herein may be derived in part or in whole from fossil sources, biological sources such as plant sources, recycled sources such as used tires, or a mixture of two or more of fossil, biological, and recycled sources.

[0025] <Pneumatic tires> Fig. 1 shows a widthwise half cross-sectional view of an example of a pneumatic tire of the present invention. The pneumatic tire 10 shown in Fig. 1 includes one or more layers, for example, one to three layers (one layer in the illustrated example) of a carcass ply 1, and one or more layers, for example, two to six layers (two layers in the illustrated example) of a belt layer 3, and the carcass ply 1 and the belt layer 3 each have cut cords arranged in parallel. Also, the symbol CL in the drawing denotes the tire equatorial plane.

[0026] As shown in FIG. 1, in the tire of the present invention, a carcass ply 1 is arranged toroidally with its side portions wrapped around a bead core 2, and a belt layer 3 is arranged radially outward of the crown portion of the carcass ply 1.

[0027] In the tire of the present invention, an auxiliary reinforcing layer 4 containing a copolymer having a conjugated diene unit and a non-conjugated olefin unit is disposed adjacent to the vicinity of the cut cord ends of at least one of the carcass ply 1 and the belt layer 3 serving as the main cord reinforcing layer, or adjacent to the vicinity of the outer end in the tire width direction of the chafer disposed outside the carcass ply in the bead portion. This auxiliary reinforcing layer 4 is disposed in a position covering at least the cut cord ends of the adjacent main cord reinforcing layer or the vicinity of the outer end in the tire width direction of the chafer from the inner and / or outer side of the tire. For example, in the example shown in FIG. 1 , the auxiliary reinforcing layer 4 is disposed adjacent to the vicinity of the cut cord ends 1a of the turned-up end of the carcass ply 1 wrapped around the bead core 2, in a position covering the cut cord ends 1a from the outer side of the tire, and extending both radially inward and outward of the cut cord ends 1a of the carcass ply 1.

[0028] By providing an auxiliary reinforcing layer containing a copolymer having conjugated diene units and non-conjugated olefin units with good crack propagation resistance adjacent to the vicinity of the cut end of the cord of at least one of the carcass ply 1 and belt layer 3 as the main cord reinforcing layer, or adjacent to the vicinity of the outer end in the tire width direction of the chafer arranged outside the carcass ply in the bead portion, it is possible to improve the durability of the tire while achieving weight reduction. As described in Patent Document 1, the provision of an auxiliary reinforcing layer is expected to protect the cord ends and improve durability, but the provision of the auxiliary reinforcing layer increases the tire weight. To address this issue, it is desirable to reduce the thickness of the auxiliary reinforcing layer, but it is difficult to stably manufacture a thin rubber sheet. Furthermore, a thin rubber sheet stretches under load, making it prone to deformation during tire manufacturing and less practical. In contrast, a sheet containing a copolymer having conjugated diene units and non-conjugated olefin units stretches less and can be manufactured more stably. Therefore, by using a sheet containing a copolymer having conjugated diene units and non-conjugated olefin units as the auxiliary reinforcing layer, it is possible to achieve both durability and weight reduction.

[0029] Here, in the present invention, the "vicinity of the cord cut end" of the main cord reinforcement layer refers to the cord region including the cord cut end. The width of this region is not particularly limited, but it preferably includes a cord section within 3 mm from the cord cut end, particularly preferably within 5 mm, and even more preferably within 8 mm from the cord cut end. That is, the length D of the overlapping portion between the main cord reinforcement layer and the auxiliary reinforcement layer 4 extending along the vicinity of the cord cut end is preferably 3 mm or more, particularly 5 mm or more, and even more preferably 8 mm or more. This length D is measured along the extending direction of the auxiliary reinforcement layer. The reason for this is that when the auxiliary reinforcement layer is disposed near the cord cut end of the main cord reinforcement layer, if the length D of the overlapping portion between the main cord reinforcement layer and the auxiliary reinforcement layer 4 extending along the vicinity of the cord cut end is less than 3 mm, it is undesirable because the auxiliary reinforcement layer 4 will not be able to bear the stress that would cause the cord end to peel off as effectively. Furthermore, if the length D of the overlapping portion between the main cord reinforcement layer and the auxiliary reinforcement layer 4 is less than 5 mm, the gaps at the cut end faces of the cords of the main cord reinforcement layer and the gaps at the end faces of the auxiliary reinforcement layer will be close to each other, causing cracks to form in the gaps and making the tire more susceptible to early failure. Furthermore, if the length D of the overlapping portion between the main cord reinforcement layer and the auxiliary reinforcement layer 4 is less than 8 mm, the overlapping portion will be in a strain region that will cause cracks to form at the cord ends of the main cord reinforcement layer, making the cut end of the auxiliary reinforcement layer more susceptible to cracks. Furthermore, "adjacent to" the vicinity of the cut cord end of the main cord reinforcement layer means that the distance between the main cord reinforcement layer and the auxiliary reinforcement layer in the thickness direction of the main cord reinforcement layer at the portion where the main cord reinforcement layer and the auxiliary reinforcement layer are parallel to each other is within 3 mm, preferably within 1 mm. If the distance between the main cord reinforcement layer and the auxiliary reinforcement layer in the thickness direction of the main cord reinforcement layer exceeds 3 mm, this is not preferable because the auxiliary reinforcement layer becomes less effective in bearing the stress that causes the cord end to peel.

[0030] In the tire of the present invention, for example, by disposing an auxiliary reinforcing layer 4 near the cut cord end 1a of the turned-up end of the carcass ply 1, it is possible to suppress the concentration of shear strain along the turned-up end of the carcass ply 1 due to thrust from the rim flange during rolling under load, and to suppress the occurrence of cracks due to rigidity differences in the carcass ply 1. Furthermore, because the cut end of the auxiliary reinforcing layer 4 according to the present invention is fused or co-vulcanized with the rubber, it is also possible to suppress the occurrence of cracks due to the cut end of the auxiliary reinforcing layer 4. Therefore, according to the present invention, it is possible to suppress the occurrence and propagation of cracks from the cut cord end of the main cord reinforcing layer and further cracks from between the main cord reinforcing layer and the auxiliary reinforcing layer without causing problems due to the auxiliary reinforcing layer 4 itself, thereby realizing a tire with improved durability and a longer life. Furthermore, by disposing an auxiliary reinforcing layer near the outer end of the chafer in the tire width direction, it is also possible to suppress the occurrence of cracks due to the outer end of the chafer in the tire width direction.

[0031] The auxiliary reinforcing layer 4 according to the present invention contains a copolymer having conjugated diene units and non-conjugated olefin units. The copolymer having conjugated diene units and non-conjugated olefin units used in the present invention has the advantage that it can be directly adhered to the rubber by heat fusion when heated during tire vulcanization.

[0032] The thickness of the auxiliary reinforcing layer 4 containing the copolymer having conjugated diene units and non-conjugated olefin units is not particularly limited, and is, for example, in one embodiment, 0.05 mm or more, in another embodiment, 0.1 mm or more, in another embodiment, 1 mm or more, in another embodiment, 5 mm or less, and in still another embodiment, 3 mm or less. The content of the copolymer in the auxiliary reinforcing layer 4 containing the copolymer is not particularly limited, but is preferably 50 mass % or more, and may be 100 mass % (i.e., an embodiment in which the auxiliary reinforcing layer 4 containing the copolymer is composed only of the copolymer).

[0033] (Copolymers having conjugated diene units and non-conjugated olefin units) The copolymer having a conjugated diene unit and a non-conjugated olefin unit may be a binary copolymer consisting of two units, a conjugated diene unit and a non-conjugated olefin unit, or may be a ternary copolymer consisting of three units including an aromatic vinyl unit, or may be a multi-component copolymer containing other monomer units.

[0034] -Conjugated diene units- The conjugated diene unit is a structural unit derived from a conjugated diene compound as a monomer. Here, the conjugated diene compound refers to a conjugated diene compound. The conjugated diene compound preferably has 4 to 8 carbon atoms. Specific examples of such conjugated diene compounds include 1,3-butadiene, isoprene, 1,3-pentadiene, and 2,3-dimethyl-1,3-butadiene. The conjugated diene compounds may be used alone or in combination of two or more.

[0035] From the viewpoint of improving the mechanical strength of the auxiliary reinforcing layer containing the copolymer, the conjugated diene compound as a monomer of the copolymer preferably contains at least one selected from the group consisting of 1,3-butadiene and isoprene, more preferably consists of only at least one selected from the group consisting of 1,3-butadiene and isoprene, and even more preferably consists of only 1,3-butadiene. In other words, the conjugated diene units in the copolymer preferably contain at least one selected from the group consisting of 1,3-butadiene units and isoprene units, more preferably consist of only at least one selected from the group consisting of 1,3-butadiene units and isoprene units, and even more preferably consist of only 1,3-butadiene units.

[0036] When the copolymer is a binary copolymer, the content of conjugated diene units is preferably more than 0 mol% and not more than 50 mol%. In this case, a copolymer excellent in elongation and weather resistance can be obtained. From the same viewpoint, the proportion of conjugated diene units in the binary copolymer is more preferably not more than 40 mol%.

[0037] In the binary copolymer, the proportion of 1,2-adducts (including 3,4-adducts) of conjugated diene units is preferably 10 mol% or less. When the proportion is 10 mol% or less, the heat resistance and flex fatigue resistance of the copolymer can be improved. From the same viewpoint, the proportion of 1,2-adducts (including 3,4-adducts) of conjugated diene units in the binary copolymer is more preferably 8 mol% or less, and even more preferably 6 mol% or less. Note that the proportion of 1,2-adducts (including 3,4-adducts) of conjugated diene units is the proportion of all conjugated diene units, not the proportion of the entire copolymer. Furthermore, when the conjugated diene units are butadiene units, the proportion has the same meaning as the 1,2-vinyl bond content.

[0038] When the copolymer is a terpolymer or a multicomponent copolymer, the content of conjugated diene units is preferably 1 mol% or more, more preferably 3 mol% or more, and even more preferably 5 mol% or more, and is preferably 50 mol% or less, more preferably 40 mol% or less, and even more preferably 35 mol% or less. When the content of the conjugated diene unit is 1 to 50 mol % of the entire copolymer, the flexibility and mechanical strength of the auxiliary reinforcing layer containing the copolymer can be improved. From the viewpoint of further improving the flexibility and mechanical strength of the auxiliary reinforcing layer containing the copolymer, the content of the conjugated diene unit is preferably in the range of 1 to 50 mol%, more preferably in the range of 3 to 40 mol%, and even more preferably in the range of 5 to 35 mol% of the entire copolymer.

[0039] -Non-conjugated olefin units- The non-conjugated olefin unit is a structural unit derived from a non-conjugated olefin compound as a monomer. Here, the non-conjugated olefin compound refers to an aliphatic unsaturated hydrocarbon compound having one or more carbon-carbon double bonds. The non-conjugated olefin compound preferably has 2 to 10 carbon atoms. Specific examples of such non-conjugated olefin compounds include α-olefins such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, and 1-octene, and heteroatom-substituted alkene compounds such as vinyl pivalate, 1-phenylthioethene, and N-vinylpyrrolidone. The non-conjugated olefin compounds may be used alone or in combination of two or more.

[0040] The non-conjugated olefin compound as a monomer of the copolymer is preferably an acyclic non-conjugated olefin compound from the viewpoint of improving the mechanical strength of the auxiliary reinforcing layer containing the copolymer, and the acyclic non-conjugated olefin compound is more preferably an α-olefin, even more preferably an α-olefin containing ethylene, and particularly preferably consisting of ethylene alone. In other words, the non-conjugated olefin units in the copolymer are preferably non-cyclic non-conjugated olefin units, and the non-cyclic non-conjugated olefin units are more preferably α-olefin units, even more preferably α-olefin units containing ethylene units, and particularly preferably consisting of only ethylene units.

[0041] When the copolymer is a binary copolymer, the content of non-conjugated olefin units is preferably 50 mol% or more and less than 100 mol%. In this case, the fracture properties at high temperatures of the auxiliary reinforcing layer containing the copolymer can be effectively improved. From the same viewpoint, the proportion of non-conjugated olefin units in the binary copolymer is more preferably 60 mol% or more.

[0042] When the copolymer is a terpolymer or a multipolymer, the content of non-conjugated olefin units is preferably 40 mol% or more, more preferably 45 mol% or more, even more preferably 55 mol% or more, particularly preferably 60 mol% or more, and is preferably 97 mol% or less, more preferably 95 mol% or less, and even more preferably 90 mol% or less. When the content of non-conjugated olefin units is 40 to 97 mol% of the entire copolymer, the mechanical strength of the auxiliary reinforcing layer containing the copolymer can be improved. From the viewpoint of further improving the mechanical strength of the auxiliary reinforcing layer containing the copolymer, the content of the non-conjugated olefin units is preferably in the range of 40 to 97 mol% of the total copolymer, more preferably in the range of 45 to 95 mol%, even more preferably in the range of 55 to 90 mol%, and even more preferably in the range of 60 to 90 mol%.

[0043] -Aromatic vinyl unit- The copolymer preferably further contains an aromatic vinyl unit. The aromatic vinyl unit is a structural unit derived from an aromatic vinyl compound as a monomer. When the copolymer contains aromatic vinyl units, crystalline components such as ethylene crystalline components are cut, and excessive crystallization resulting from non-conjugated olefin units is suppressed. This improves the rigidity of the copolymer while preventing loss of elasticity and achieving high crack resistance, thereby improving the crack resistance of the auxiliary reinforcing layer containing the copolymer. Here, the aromatic vinyl compound refers to an aromatic compound substituted with at least a vinyl group, and is not included in conjugated diene compounds. The aromatic vinyl compound preferably has 8 to 10 carbon atoms. Examples of such aromatic vinyl compounds include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, o,p-dimethylstyrene, o-ethylstyrene, m-ethylstyrene, and p-ethylstyrene. The aromatic vinyl compounds may be used alone or in combination of two or more.

[0044] From the viewpoint of improving the mechanical strength of the auxiliary reinforcing layer containing the copolymer, the aromatic vinyl compound as a monomer of the copolymer preferably contains styrene, and more preferably consists of styrene alone. In other words, the aromatic vinyl unit in the copolymer preferably contains styrene, and more preferably consists of styrene alone. The aromatic ring in the aromatic vinyl unit is not included in the main chain of the copolymer unless it is bonded to an adjacent unit.

[0045] When the copolymer is a terpolymer or a multicomponent copolymer, the content of aromatic vinyl units is preferably 2 mol% or more, and preferably 35 mol% or less, more preferably 30 mol% or less, and even more preferably 25 mol% or less. When the content of aromatic vinyl units is 2 to 35 mol% of the entire copolymer, the mechanical strength of the auxiliary reinforcing layer containing the copolymer can be improved. From the viewpoint of further improving the mechanical strength of the auxiliary reinforcing layer containing the copolymer, the content of aromatic vinyl units is preferably in the range of 2 to 35 mol% of the entire copolymer, more preferably in the range of 2 to 30 mol%, and even more preferably in the range of 2 to 25 mol%.

[0046] From the viewpoint of obtaining the desired effects of the present invention, the content of other structural units than the conjugated diene unit, non-conjugated olefin unit, and aromatic vinyl unit is preferably 30 mol% or less of the entire copolymer, more preferably 20 mol% or less, and even more preferably 10 mol% or less, and it is particularly preferable that no other structural units are contained, i.e., the content is 0 mol%. In other words, the copolymer is preferably a binary copolymer consisting of two units, a conjugated diene unit and a non-conjugated olefin unit, or a ternary copolymer consisting of three units, a conjugated diene unit, a non-conjugated olefin unit, and an aromatic vinyl unit. In addition, from the viewpoint of reliably obtaining the desired effects, the copolymer preferably has a butylene unit content of 0 mol %.

[0047] From the viewpoint of improving the mechanical strength of the auxiliary reinforcing layer containing the copolymer, it is preferable that the copolymer is a polymer obtained by polymerizing at least one type of conjugated diene compound, one type of non-conjugated olefin compound, and one type of aromatic vinyl compound as monomers. In other words, the copolymer is preferably a copolymer containing only one type of conjugated diene unit, only one type of non-conjugated olefin unit, and only one type of aromatic vinyl unit, more preferably a terpolymer consisting of only one type of conjugated diene unit, only one type of non-conjugated olefin unit, and only one type of aromatic vinyl unit, and even more preferably a terpolymer consisting of only 1,3-butadiene units, ethylene units, and styrene units. Here, "only one type of conjugated diene unit" includes conjugated diene units with different bonding modes.

[0048] For example, when the copolymer is a binary copolymer, it is preferable that the content of conjugated diene units is more than 0 mol% and not more than 50 mol%, and the content of non-conjugated olefin units is 50 mol% or more and less than 100 mol%. In this case, a copolymer excellent in elongation and weather resistance can be obtained, and the fracture properties at high temperatures of the auxiliary reinforcing layer containing the copolymer can be effectively improved.

[0049] Furthermore, when the copolymer is, for example, a terpolymer, it is preferable that the content of conjugated diene units is 1 to 50 mol%, the content of non-conjugated olefin units is 40 to 97 mol%, and the content of aromatic vinyl units is 2 to 35 mol%, which can improve the flexibility and mechanical strength of the auxiliary reinforcing layer containing the copolymer.

[0050] -Physical properties of copolymers- The copolymer preferably has a polystyrene-equivalent number average molecular weight (Mn) of 10,000 to 9,000,000 (10 to 9,000 kg / mol), more preferably 100,000 to 8,000,000 (100 to 8,000 kg / mol). When the copolymer has an Mn of 10,000 or more, the mechanical strength of the auxiliary reinforcing layer containing the copolymer can be sufficiently ensured, and when the Mn is 9,000,000 or less, the workability of the copolymer itself or a composition containing the copolymer is unlikely to be impaired.

[0051] The copolymer preferably has a polystyrene-equivalent weight average molecular weight (Mw) of 10,000 to 10,000,000 (10 to 10,000 kg / mol), more preferably 50,000 to 9,000,000 (50 to 9,000 kg / mol), and even more preferably 100,000 to 8,000,000 (100 to 8,000 kg / mol). Having an Mw of 10,000 or more ensures sufficient mechanical strength for the auxiliary reinforcing layer containing the copolymer, while having an Mw of 10,000,000 or less prevents the workability of the copolymer itself or a composition containing the copolymer from being impaired.

[0052] The copolymer preferably has a molecular weight distribution [Mw / Mn (weight average molecular weight / number average molecular weight)] of 1.00 to 4.00, more preferably 1.00 to 3.50, and even more preferably 1.80 to 3.00. When the molecular weight distribution of the copolymer is 4.00 or less, sufficient uniformity can be achieved in the physical properties of the copolymer.

[0053] The number average molecular weight (Mn), weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of the copolymer are determined by gel permeation chromatography (GPC) using polystyrene as a standard substance.

[0054] The copolymer preferably has an endothermic peak energy of 10 to 150 J / g, more preferably 30 to 120 J / g, as measured by a differential scanning calorimeter (DSC) at 0 to 120°C. If the endothermic peak energy of the copolymer is 10 J / g or more, the crystallinity of the copolymer is high, and the crack resistance of the auxiliary reinforcing layer containing the copolymer can be improved. Furthermore, if the endothermic peak energy of the copolymer is 150 J / g or less, the workability of the copolymer itself or a composition containing the copolymer is improved. The endothermic peak energy of the copolymer may be measured using a differential scanning calorimeter in accordance with JIS K 7121-1987, for example, by increasing the temperature from -150°C to 150°C at a rate of 10°C / min.

[0055] The copolymer preferably has a melting point of 50 to 120°C, more preferably 50 to 110°C. If the melting point of the copolymer is 50°C or higher, the crystallinity of the copolymer is high, and the crack resistance of the auxiliary reinforcing layer containing the copolymer can be improved. If the melting point of the copolymer is 120°C or lower, the workability of the copolymer itself or a composition containing the copolymer is improved. If the melting point of the copolymer is 50 to 120°C, the crack resistance of the auxiliary reinforcing layer containing the copolymer is high, and the workability in manufacturing the auxiliary reinforcing layer containing the copolymer is improved. The melting point of the copolymer may be measured using a differential scanning calorimeter (DSC) in accordance with JIS K 7121-1987.

[0056] The copolymer preferably has a glass transition temperature (Tg) measured by a differential scanning calorimeter (DSC) of 0° C. or lower, more preferably −110° C. to −10° C. If the copolymer has a glass transition temperature of 0° C. or lower, the mechanical strength of the auxiliary reinforcing layer containing the copolymer can be further improved. The glass transition temperature of the copolymer may be measured using a differential scanning calorimeter in accordance with JIS K 7121-1987.

[0057] The copolymer preferably has a crystallinity of 0.5 to 50%, more preferably 3 to 45%, and even more preferably 5 to 45%. When the copolymer has a crystallinity of 0.5% or more, the crystallinity of the copolymer resulting from the non-conjugated olefin units can be sufficiently ensured, further improving the mechanical strength of the auxiliary reinforcing layer containing the copolymer. Furthermore, when the copolymer has a crystallinity of 50% or less, the workability and extrusion processability during kneading of the copolymer itself or a composition containing the copolymer are improved. The crystallinity of the copolymer can be determined by measuring the crystalline melting energy of 100% crystalline polyethylene and the melting peak energy of the copolymer, and calculating the crystallinity from the energy ratio between the polyethylene and the copolymer. The melting peak energy can also be measured using a differential scanning calorimeter.

[0058] The copolymer preferably has a main chain consisting solely of acyclic structures, which can further improve the mechanical strength of the auxiliary reinforcing layer containing the copolymer. NMR is the main measurement method used to confirm whether the main chain of the copolymer has a cyclic structure. Specifically, if no peaks derived from the cyclic structure present in the main chain (for example, peaks appearing at 10 to 24 ppm for three- to five-membered rings) are observed, this indicates that the main chain of the copolymer is composed solely of acyclic structures. In this specification, the main chain of a polymer refers to a linear molecular chain to which all other molecular chains (long molecular chains, short molecular chains, or both) are connected like pendants (see Section 1.34 of "Glossary of Basic Terms in Polymer Science IUPAC Recommendations 1996," Pure Appl. Chem., 68, 2287-2311 (1996)). The copolymer may have either a linear or branched structure, but preferably has a linear structure.

[0059] The copolymer has excellent mechanical strength, specifically excellent breaking strength, puncture strength, tensile strength, abrasion resistance, crack resistance, impact resistance, etc. The copolymer also has excellent mechanical strength at low temperatures. Furthermore, the copolymer has excellent mechanical strength without relying on fillers such as carbon black, silica, etc., and therefore can be colored with a colorant, resulting in excellent decorative properties. On the other hand, the copolymer can interact with fillers, so that the mechanical strength can be further improved by using a filler. The copolymer contains conjugated diene units, and therefore is crosslinkable. The copolymer contains conjugated diene units, and therefore functions as an elastic body, being stretchable. The copolymer can be injection molded and stretched, and therefore can be processed into a film. The copolymer contains conjugated diene units and non-conjugated olefin units, and therefore easily adheres to both resins (olefin resins) and rubbers (diene rubbers), and can therefore function as an adhesive between resins and rubbers. The copolymer is also foamable. As described above, the copolymer preferably has a melting point of 50 to 120°C, and can restore its shape by pouring hot water of about 80 to 100°C over it or by immersing it in hot water. The copolymer also has shape-memory properties.

[0060] - Copolymer manufacturing method - When producing a binary copolymer consisting of two units, a conjugated diene unit and a non-conjugated olefin unit, as the copolymer, the copolymer can be produced through a polymerization step using a conjugated diene compound and a non-conjugated olefin compound as monomers. Furthermore, when producing a terpolymer consisting of three units, i.e., a conjugated diene unit, a non-conjugated olefin unit, and an aromatic vinyl unit, as the copolymer, the copolymer can be produced through a polymerization step using a conjugated diene compound, a non-conjugated olefin compound, and an aromatic vinyl compound as monomers.

[0061] The method for producing the copolymer may further include a coupling step, a washing step, and other steps, if necessary. Hereinafter, the method for producing a copolymer will be described, taking the case of producing a terpolymer as an example.

[0062] In the production of copolymers, it is preferable to first polymerize only a non-conjugated olefin compound and an aromatic vinyl compound in the presence of a polymerization catalyst without adding a conjugated diene compound. In particular, when using a catalyst composition described below, the conjugated diene compound is more reactive than the non-conjugated olefin compound and the aromatic vinyl compound, making it difficult to polymerize either or both of the non-conjugated olefin compound and the aromatic vinyl compound in the presence of the conjugated diene compound. Furthermore, due to the characteristics of the catalyst, it is also difficult to first polymerize the conjugated diene compound and then additionally polymerize the non-conjugated olefin compound and the aromatic vinyl compound.

[0063] The polymerization method may be any method such as solution polymerization, suspension polymerization, liquid phase bulk polymerization, emulsion polymerization, gas phase polymerization, solid phase polymerization, etc. When a solvent is used in the polymerization reaction, any solvent may be used as long as it is inert in the polymerization reaction, and examples thereof include toluene, cyclohexane, and normal hexane.

[0064] The polymerization step may be carried out in one stage or in two or more stages. The one-stage polymerization process is a process in which all types of monomers to be polymerized, i.e., a conjugated diene compound, a non-conjugated olefin compound, an aromatic vinyl compound, and other monomers, preferably a conjugated diene compound, a non-conjugated olefin compound, and an aromatic vinyl compound, are reacted and polymerized simultaneously. A multi-stage polymerization process is a process in which one or two types of monomers are first reacted in part or in whole to form a polymer (first polymerization stage), and then one or more stages (second polymerization stage to final polymerization stage) are carried out in which monomers that were not added in the first polymerization stage, the remainder of the monomers added in the first polymerization stage, etc. are added and polymerized. In particular, in the production of the copolymer, it is preferable to carry out the polymerization process in multiple stages.

[0065] In the polymerization step, the polymerization reaction is preferably carried out in an atmosphere of an inert gas, preferably nitrogen gas or argon gas. The temperature of the polymerization reaction is not particularly limited, but is preferably in the range of -100°C to 200°C, and can also be around room temperature. The pressure of the polymerization reaction is preferably in the range of 0.1 to 10.0 MPa in order to sufficiently incorporate the conjugated diene compound into the polymerization reaction system. The reaction time for the polymerization reaction is not particularly limited, and is preferably in the range of 1 second to 10 days, but can be appropriately selected depending on conditions such as the type of polymerization catalyst and polymerization temperature. In the polymerization step of the conjugated diene compound, the polymerization may be terminated using a polymerization terminator such as methanol, ethanol, or isopropanol.

[0066] The polymerization process is preferably carried out in multiple stages. More preferably, the process comprises a first step of mixing a first monomer raw material containing at least an aromatic vinyl compound with a polymerization catalyst to obtain a polymerization mixture, and a second step of introducing a second monomer raw material containing at least one selected from the group consisting of a conjugated diene compound, a non-conjugated olefin compound, and an aromatic vinyl compound into the polymerization mixture. Furthermore, it is more preferable that the first monomer raw material does not contain a conjugated diene compound, and the second monomer raw material contains a conjugated diene compound.

[0067] The first monomer starting material used in the first step may contain a non-conjugated olefin compound together with an aromatic vinyl compound. The first monomer starting material may contain the entire amount of the aromatic vinyl compound used, or may contain only a portion of the aromatic vinyl compound. The non-conjugated olefin compound is contained in at least one of the first monomer starting material and the second monomer starting material.

[0068] The first step is preferably carried out in a reactor under an atmosphere of an inert gas, preferably nitrogen gas or argon gas. The temperature (reaction temperature) in the first step is not particularly limited, but is preferably in the range of -100°C to 200°C, and can also be around room temperature. The pressure in the first step is also not particularly limited, but is preferably in the range of 0.1 to 10.0 MPa in order to sufficiently incorporate the aromatic vinyl compound into the polymerization reaction system. The time spent in the first step (reaction time) can be appropriately selected depending on conditions such as the type of polymerization catalyst and the reaction temperature, but is preferably in the range of 5 to 500 minutes when the reaction temperature is 25 to 80°C.

[0069] In the first step, any polymerization method can be used to obtain the polymerization mixture, such as solution polymerization, suspension polymerization, liquid phase bulk polymerization, emulsion polymerization, gas phase polymerization, solid phase polymerization, etc. When a solvent is used in the polymerization reaction, any solvent that is inert in the polymerization reaction can be used, and examples of the solvent include toluene, cyclohexanone, and normal hexane.

[0070] The second monomer raw material used in the second step is preferably a conjugated diene compound alone, or a conjugated diene compound and a non-conjugated olefin compound, or a conjugated diene compound and an aromatic vinyl compound, or a conjugated diene compound, a non-conjugated olefin compound and an aromatic vinyl compound. When the second monomer raw material contains at least one selected from the group consisting of a non-conjugated olefin compound and an aromatic vinyl compound in addition to a conjugated diene compound, these monomer raw materials may be mixed together with a solvent or the like before being introduced into the polymerization mixture, or each monomer raw material may be introduced individually. Moreover, each monomer raw material may be added simultaneously or sequentially. In the second step, the method for introducing the second monomer raw material into the polymerization mixture is not particularly limited, but it is preferable to control the flow rate of each monomer raw material and add it continuously to the polymerization mixture (so-called metering). Here, when a monomer raw material that is gaseous under the conditions of the polymerization reaction system (for example, ethylene as a non-conjugated olefin compound under the conditions of room temperature and normal pressure) is used, it can be introduced into the polymerization reaction system at a predetermined pressure.

[0071] The second step is preferably carried out in a reactor under an atmosphere of an inert gas, preferably nitrogen gas or argon gas. The temperature (reaction temperature) in the second step is not particularly limited, but is preferably in the range of -100°C to 200°C, and can also be set to about room temperature. Note that increasing the reaction temperature may decrease the selectivity of cis-1,4 bonds in the conjugated diene units. The pressure in the second step is not particularly limited, but is preferably in the range of 0.1 to 10.0 MPa in order to sufficiently incorporate monomers such as conjugated diene compounds into the polymerization reaction system. The time spent in the second step (reaction time) can be appropriately selected depending on conditions such as the type of polymerization catalyst and reaction temperature, but is preferably in the range of 0.1 hours to 10 days, for example. In the second step, the polymerization reaction may be terminated using a polymerization terminator such as methanol, ethanol, or isopropanol.

[0072] Here, the polymerization step of the above-mentioned conjugated diene compound, non-conjugated olefin compound, and aromatic vinyl compound preferably includes a step of polymerizing various monomers in the presence of one or more of the following components (a) to (f) as catalyst components. Note that, although it is preferable to use one or more of the following components (a) to (f) in the polymerization step, it is more preferable to use a combination of two or more of the following components (a) to (f) as a catalyst composition. Component (a): a rare earth element compound or a reaction product of the rare earth element compound with a Lewis base (b) Component: Organometallic compound (c) Component: Aluminoxane (d) Component: Ionic compound (e) Component: Halogen compound (f) Component: a cyclopentadiene skeleton-containing compound selected from substituted or unsubstituted cyclopentadiene (a compound having a cyclopentadienyl group), substituted or unsubstituted indene (a compound having an indenyl group), and substituted or unsubstituted fluorene (a compound having a fluorenyl group). The above components (a) to (f) can be used in the polymerization step by referring to, for example, International Publication No. 2018 / 092733.

[0073] The coupling step is a step of carrying out a reaction (coupling reaction) to modify at least a part (for example, an end) of the polymer chain of the copolymer obtained in the polymerization step. In the coupling step, it is preferable to carry out the coupling reaction when the polymerization reaction reaches 100%. The coupling agent used in the coupling reaction is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include tin-containing compounds such as bis(1-octadecylmaleate)dioctyltin(IV), isocyanate compounds such as 4,4'-diphenylmethane diisocyanate, alkoxysilane compounds such as glycidylpropyltrimethoxysilane, etc. These may be used alone or in combination of two or more. Among these, bis(1-octadecylmaleate)dioctyltin(IV) is preferred in terms of reaction efficiency and low gel formation. By carrying out the coupling reaction, the number average molecular weight (Mn) of the copolymer can be increased.

[0074] The washing step is a step of washing the copolymer obtained in the polymerization step. The medium used for washing is not particularly limited and can be selected appropriately depending on the purpose. Examples include methanol, ethanol, and isopropanol. However, when using a Lewis acid-derived catalyst as the polymerization catalyst, an acid (e.g., hydrochloric acid, sulfuric acid, nitric acid, etc.) can be added to these solvents. The amount of acid added is preferably 15 mol% or less relative to the solvent. By adding an amount of 15 mol% or less, the acid is less likely to remain in the copolymer and to adversely affect the reaction during kneading and vulcanization of the composition. This washing step can suitably reduce the amount of catalyst residue in the copolymer.

[0075] (Other ingredients) The auxiliary reinforcing layer containing the copolymer may contain polymer components other than the copolymer having conjugated diene units and non-conjugated olefin units, as well as various compounding agents. Examples of the polymer components include olefin resins and rubber components. Examples of the compounding agents include functional components such as fillers, reinforcing fibers, antioxidants, softeners, crosslinking packages containing stearic acid, zinc oxide, crosslinking accelerators, and crosslinking agents, resins, ultraviolet absorbers, foaming agents, and colorants.

[0076] -Olefin resin- The auxiliary reinforcing layer containing the copolymer may contain an olefin-based resin. Here, the olefin-based resin excludes the copolymer having the conjugated diene unit and the non-conjugated olefin unit. By containing the olefin-based resin in the auxiliary reinforcing layer containing the copolymer, the abrasion resistance and impact resistance of the auxiliary reinforcing layer containing the copolymer are improved.

[0077] The olefin resin refers to a resin in which at least polyolefin has crystallinity and constitutes the main part of the resin. For example, olefin-α-olefin copolymers, olefin copolymers, etc. can be mentioned, and they may be modified. Specifically, polyethylene, ethylene-propylene copolymer, ethylene-hexene copolymer, ethylene-pentene copolymer, ethylene-octene copolymer, propylene-1-hexene copolymer, ethylene-4-methyl-pentene copolymer, propylene-4-methyl-1-pentene copolymer, ethylene-butene copolymer, propylene-butene copolymer, 1-butene-hexene copolymer, 1-butene-4-methyl-pentene copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl methacrylate copolymer, ethylene-ethyl methacrylate copolymer, ethylene Examples of the polymer include propylene-butyl methacrylate copolymer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-butyl acrylate copolymer, ethylene-vinyl acetate copolymer, propylene-methacrylic acid copolymer, propylene-methyl methacrylate copolymer, propylene-ethyl methacrylate copolymer, propylene-butyl methacrylate copolymer, propylene-methyl acrylate copolymer, propylene-ethyl acrylate copolymer, propylene-butyl acrylate copolymer, and propylene-vinyl acetate copolymer.

[0078] The olefin resin preferably contains a non-conjugated olefin unit. When the olefin resin contains a non-conjugated olefin unit, cracks are less likely to occur in the auxiliary reinforcing layer containing the copolymer. The olefin resin preferably contains an olefin unit having 2 to 5 carbon atoms, and more preferably, the difference in carbon number between the non-conjugated olefin unit contained in the copolymer and the non-conjugated olefin unit contained in the olefin resin is 2 or less. When the copolymer and the olefin resin contain a non-conjugated olefin unit, which is a common unit, and the non-conjugated olefin unit has a similar structure, the mechanical strength of the auxiliary reinforcing layer containing the copolymer is further improved.

[0079] The difference between the number of carbon atoms of the non-conjugated olefin units contained in the copolymer and the number of carbon atoms of the non-conjugated olefin units contained in the olefin-based resin is more preferably 1 or less, and even more preferably 0. The number of carbon atoms of the olefin units is more preferably 2 to 4, and more preferably 2 to 3, i.e., polyethylene-based resins and polypropylene-based resins are more preferred.

[0080] The polyethylene-based resin refers to a polymer containing ethylene units as the main component (e.g., more than 50 mol%) in the main chain, and may further contain other units such as propylene units. The polyethylene-based resin may be either thermosetting or thermoplastic. Specific examples include polyethylene (homopolymer) and ethylene-propylene copolymer (provided that the ethylene unit is more than 50 mol%). The polyethylene-based resin may be of various types, such as very low-density polyethylene (VLDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), and high-density polyethylene (HDPE), and any of these may be used. Among these, from the viewpoint of high versatility, it is preferable to use one or more polyethylene-based resins selected from the group consisting of high-density polyethylene (HDPE) and linear low-density polyethylene (LLDPE).

[0081] The polypropylene-based resin refers to a polymer containing propylene units as a main component (for example, more than 50 mol%) in the main chain, and may further contain other units such as ethylene units. The polypropylene-based resin may be thermosetting or thermoplastic. Specific examples include polypropylene (homopolymer) and ethylene-propylene copolymer (provided that the propylene units are more than 50 mol%).

[0082] From the viewpoint of improving the mechanical strength of the auxiliary reinforcing layer containing the copolymer, the olefin-based resin preferably has a number average molecular weight (Mn) in terms of polystyrene of 5 to 10,000 kg / mol, more preferably 7 to 1,000 kg / mol, and even more preferably 10 to 1,000 kg / mol.

[0083] From the viewpoint of improving the mechanical strength of the auxiliary reinforcing layer containing the copolymer, the olefin-based resin preferably has a weight average molecular weight (Mw) in terms of polystyrene of 100 to 300 kg / mol, more preferably 180 to 300 kg / mol, and even more preferably 200 to 280 kg / mol. The number average molecular weight (Mn) and weight average molecular weight (Mw) of the olefin resin can be measured by gel permeation chromatography (GPC). For example, a GPC (gel permeation chromatography) such as "HLC-8321GPC / HT" manufactured by Tosoh Corporation can be used.

[0084] -Rubber component- The auxiliary reinforcing layer containing the copolymer may contain a rubber component, excluding the copolymer having a conjugated diene unit and a non-conjugated olefin unit, which provides rubber elasticity to the auxiliary reinforcing layer containing the copolymer. Examples of the rubber component include natural rubber (NR) and diene rubbers such as synthetic diene rubbers. Specific examples of synthetic diene rubbers include synthetic isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), chloroprene rubber (CR), halogenated butyl rubber, and acrylonitrile-butadiene rubber (NBR). The diene rubbers may be used alone or in combination of two or more. The diene rubbers may also be modified. The rubber component may contain a non-diene rubber.

[0085] -Filler- The auxiliary reinforcing layer containing the copolymer may contain a filler. By containing a filler in the auxiliary reinforcing layer containing the copolymer, the mechanical strength of the auxiliary reinforcing layer containing the copolymer can be improved. The fillers include carbon black and inorganic fillers. The type of carbon black is not particularly limited, and examples thereof include GPF, FEF, HAF, ISAF, and SAF, with HAF, ISAF, and SAF being preferred. Examples of the inorganic filler include metal oxides such as silica, alumina, and titania, and among these, silica is preferred. The type of silica is not particularly limited, and examples include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), and colloidal silica. When silica is contained as a filler, the auxiliary reinforcing layer containing the copolymer may further contain a silane coupling agent to improve the dispersibility of the silica in the auxiliary reinforcing layer containing the copolymer.

[0086] -Anti-aging agent- The auxiliary reinforcing layer containing the copolymer may contain an antioxidant, such as an amine-ketone compound, an imidazole compound, an amine compound, a phenol compound, a sulfur compound, or a phosphorus compound.

[0087] -Softener- The auxiliary reinforcing layer containing the copolymer may contain a softener. Examples of the softener include petroleum-based softeners such as process oil, lubricating oil, naphthenic oil, paraffin, liquid paraffin, petroleum asphalt, and Vaseline; fatty oil-based softeners such as castor oil, linseed oil, rapeseed oil, and coconut oil; and waxes such as beeswax, carnauba wax, and lanolin. These softeners may be used alone or in combination of two or more.

[0088] -Crosslinking agent- The auxiliary reinforcing layer containing the copolymer may contain a crosslinking agent, which is not particularly limited and typically includes peroxides, sulfur, oximes, amines, ultraviolet curing agents, etc. The copolymer contains conjugated diene units and can be crosslinked (vulcanized) with sulfur, such as powdered sulfur, precipitated sulfur, colloidal sulfur, surface-treated sulfur, and insoluble sulfur.

[0089] -Crosslinking accelerator- The auxiliary reinforcing layer containing the copolymer may contain a crosslinking accelerator (vulcanization accelerator), such as guanidine-based, sulfenamide-based, thiuram-based, thiazole-based, aldehyde amine-based, and thiocarbamate-based crosslinking accelerators.

[0090] (Method of manufacturing auxiliary reinforcing layer containing copolymer) The auxiliary reinforcing layer containing the copolymer may be produced by using the copolymer having the conjugated diene unit and the non-conjugated olefin unit as is, or by mixing any additive component in addition to the copolymer. Alternatively, the copolymer may be produced by kneading the copolymer alone or together with any other additive components using a kneader such as a single-screw extrusion kneader, a twin-screw extrusion kneader, a Banbury mixer, a roll, or an internal mixer. The kneading of the components may be carried out in one stage or in two or more stages. When the auxiliary reinforcing layer containing the copolymer is formed from a composition containing the copolymer and other optional additive components, the composition may contain, in addition to the copolymer, the above-mentioned olefin resin, rubber component, filler, silane coupling agent, antioxidant, softener, crosslinking agent, crosslinking accelerator, etc. Here, the content of the copolymer in the composition is not particularly limited, but is preferably 50 mass% or more.

[0091] When the components of the composition are melt-kneaded in an extrusion kneader and the composition is extruded, the extruded composition may be directly cut into pellets, or the extruded composition may be formed into strands and then cut into pellets using a pelletizer. The pellets may have common shapes such as cylindrical, prismatic, and spherical shapes.

[0092] The auxiliary reinforcing layer containing the copolymer may be produced by melt-kneading the composition and then extruding it, or by hot-pressing the composition. The heat pressing temperature is preferably 120 to 160°C, and more preferably 130 to 150°C.

[0093] In the tire of the present invention, an auxiliary reinforcing layer is disposed adjacent to the vicinity of the cut cord end of the main cord reinforcing layer, in a position that covers at least the adjacent cut cord end of the main cord reinforcing layer from the inside and / or outside of the tire, and this auxiliary reinforcing layer may contain a copolymer having conjugated diene units and non-conjugated olefin units, and its internal structure is the same as that of a general pneumatic tire and can be appropriately determined as desired.

[0094] The tire 10 shown in Fig. 1 described above comprises a pair of bead portions 5, a pair of sidewall portions 6 continuing radially outward from the pair of bead portions 5, and a tread portion 7 extending between the pair of sidewall portions 6 to form a ground-contact patch. The tire 10 shown in the figure has a skeleton of one or more carcass plies 1 extending in a toroidal shape between bead cores 2 embedded in the pair of bead portions 5, and one or more belt layers 3 arranged radially outward from the crown portions of the carcass ply 1. Although not shown, an inner liner is disposed radially inward of the carcass ply 1, and bead fillers 8 are usually disposed radially outward of the bead cores 2.

[0095] (Another example of a pneumatic tire) 2 to 9 are widthwise partial cross-sectional views showing other examples of the pneumatic tire of the present invention. In a tire 20 shown in Fig. 2, auxiliary reinforcing layers 14A and 14B are disposed adjacent to the vicinity of the cord cut ends 11a at the turned-up end of the carcass ply 11 serving as the main cord reinforcing layer, in positions that sandwich and cover the cord cut ends 11a from both the outer and inner sides of the tire, and extend radially inward and outward from the cord cut ends 11a of the carcass ply 11. In this manner, in the present invention, the auxiliary reinforcing layers may be disposed on the tire inner side of the cord cut ends 11a. This also achieves the effect of suppressing cracks from occurring at the cord cut ends 11a at the turned-up end of the carcass ply 11. Note that reference numerals 12 and 18 indicate bead cores and bead fillers, respectively.

[0096] 3, the auxiliary reinforcing layer 24 is disposed adjacent to the vicinity of the cord cut end 21a at the turned-up end of the carcass ply 21 serving as the main cord reinforcing layer, and is disposed in a position that wraps around the cord cut end 21a from the radially outer side of the tire, covering the outer and inner sides of the tire, and extends radially inward of the cord cut end 21a of the carcass ply 21. In this case, too, it is possible to obtain the effect of suppressing the occurrence of cracks from the cord cut end 21a at the turned-up end of the carcass ply 21. Reference numeral 22 denotes a bead core, and 28 denotes a bead filler.

[0097] Furthermore, in the tire 40 shown in Fig. 4, the auxiliary reinforcing layers 34A and 34B are disposed adjacent to the vicinity of the cord cut ends 33a of the belt layer 33 as the main cord reinforcing layer, at positions that cover the cord cut ends 33a so as to sandwich them from the outside of the tire, and extend both inward and outward in the tire width direction than the cord cut ends 33a of the belt layer 33. In this case as well, the effect of suppressing the occurrence of cracks from the cord cut ends 33a of the belt layer 33 can be obtained. Note that the reference numeral 31 denotes a carcass ply.

[0098] Furthermore, in a tire 50 shown in Fig. 5, an auxiliary reinforcing layer 44 is disposed adjacent to the vicinity of a cord cut end 43a of a part of the belt layer 43 serving as the main cord reinforcing layer, and is disposed in a position that covers the cord cut end 43a from the outer side in the tire width direction, wrapping around the cord cut end 43a from the outer side in the tire width direction, and covering the tire from the inner and outer sides, and extending more inward in the tire width direction than the cord cut end 43a of the belt layer 43. In this case as well, the effect of suppressing the occurrence of cracks from the cord cut end 43a of the belt layer 43 can be obtained. Note that reference numeral 41 denotes a carcass ply.

[0099] 4 and 5, the auxiliary reinforcing layer is preferably disposed in the vicinity of the cut ends of the cords of at least one of the belt layers. By disposing the auxiliary reinforcing layer containing a copolymer having conjugated diene units and non-conjugated olefin units in the vicinity of the cut ends of the cords of at least one of the belt layers, it is possible to effectively suppress the occurrence of cracks from the cut ends of the cords of the belt layer and also to achieve a reduction in the weight of the tire.

[0100] Furthermore, in a tire 60 shown in Fig. 6, an auxiliary reinforcing layer 54 is disposed adjacent to the vicinity of the cord cut end 51a at the turned-up end of the carcass ply 51 serving as the main cord reinforcing layer, in a position covering the cord cut end 51a from the inside of the tire, and extending both radially inward and outward from the cord cut end 51a of the carcass ply 51. As described above, in the present invention, an auxiliary reinforcing layer may be disposed on the tire inside of the cord cut end 51a. In this case, too, the effect of suppressing cracks from occurring at the cord cut end 51a at the turned-up end of the carcass ply 51 can be obtained. Note that reference numerals 52 and 58 indicate bead cores and bead fillers, respectively.

[0101] Furthermore, in a tire 70 shown in Fig. 7, an auxiliary reinforcing layer 64 is disposed adjacent to the vicinity of a cord cut end 63a of a part of the belt layer 63 serving as a main cord reinforcing layer, in a position covering the cord cut end 63a from the outer side in the tire width direction, and extending more inward in the tire width direction than the cord cut end 63a of the belt layer 63. In this case as well, it is possible to obtain the effect of suppressing the occurrence of cracks from the cord cut end 63a of the belt layer 63. Reference numeral 61 denotes a carcass ply.

[0102] Furthermore, in a tire 80 shown in Fig. 8, an auxiliary reinforcing layer 74 is disposed adjacent to the vicinity of a cord cut end 73a of a part of the belt layer 73 serving as a main cord reinforcing layer, in a position covering the cord cut end 73a from the outer side in the tire width direction, and extending more inward in the tire width direction than the cord cut end 73a of the belt layer 73. In this case as well, the effect of suppressing the occurrence of cracks from the cord cut end 73a of the belt layer 73 can be obtained. Note that reference numeral 71 denotes a carcass ply.

[0103] Furthermore, in a tire 90 shown in Fig. 9, an auxiliary reinforcing layer 84 is disposed adjacent to the vicinity of a cord cut end 83a of a part of the belt layer 83 serving as a main cord reinforcing layer, in a position covering the cord cut end 83a from the inner side in the tire width direction, and extending more inward in the tire width direction than the cord cut end 83a of the belt layer 83. In this case as well, it is possible to obtain the effect of suppressing the occurrence of cracks from the cord cut end 83a of the belt layer 83. Reference numeral 81 denotes a carcass ply.

[0104] In the present invention, when there are multiple cord reinforcement layers, the effects of the present invention can be obtained as long as the auxiliary reinforcement layer is arranged adjacent to at least a part of the cord reinforcement layers. However, it is preferable to arrange the auxiliary reinforcement layer on the cord reinforcement layer located on the radially outer side of the tire where the centrifugal force load is large when the tire rolls, or on the cord reinforcement layer located on the widthwise outer side of the tire where the strain due to the lateral stress of the tire is large when the tire is curved, etc.

[0105] The present invention is not limited to any particular type of tire, and although the tires shown in FIGS. 1 to 9 are tires for passenger cars, the present invention can be applied to any type of tire, such as tires for trucks and buses, large tires, and the like.

[0106] FIG. 10 is a widthwise cross-sectional view of one side of a truck / bus tire according to another embodiment of the present invention. The tire 100 shown in the figure comprises a tread portion 97 forming a ground-contacting portion, a pair of sidewall portions 96 extending radially inward from both sides of the tread portion 97, and bead portions 95 continuing from the inner periphery of each sidewall portion 96. The tread portion 97, sidewall portions 96, and bead portions 95 are reinforced by a carcass consisting of at least one carcass ply 91 (two carcass plies in the illustrated example) extending toroidally from one bead portion 95 to the other. In the truck / bus tire 100 shown in the figure, a bead core 92 is embedded in each of the pair of bead portions 95, and the carcass 91 is folded back around the bead core 92 from the inside to the outside of the tire and secured thereto. Furthermore, a bead filler 98 is disposed radially outward of the bead core 92.

[0107] 10, auxiliary reinforcing layers 94A, 94B are disposed adjacent to the vicinity of the cord cut ends 91a at the turned-up ends of two carcass plies 91 serving as main cord reinforcing layers, and are disposed in positions that enclose the cord cut ends 91a from the outer side in the tire radial direction, covering the outer and inner sides of the tire, and extending radially inward of the cord cut ends 91a of the carcass ply 91. In this case as well, the effect of suppressing the occurrence of cracks from the cord cut ends 91a at the turned-up ends of the carcass ply 91 can be obtained.

[0108] In a tire 110 shown in Fig. 11, auxiliary reinforcing layers 104A, 104B are disposed adjacent to and near the cord cut ends 101a at the turned-up ends of a carcass ply 101 serving as a main cord reinforcing layer and the tire widthwise outer ends 109a of chafers 109 disposed outside the carcass ply 101 in the bead portion, and are disposed in positions that enclose the cord cut ends 101a and the tire widthwise outer ends 109a from the tire radially outer side, covering them from the tire outer and inner sides, and extend radially inward of the cord cut ends 101a or the tire widthwise outer ends 109a of the carcass ply 101. This also provides the effect of suppressing cracks from occurring at the cord cut ends 101a at the turned-up ends of the carcass ply 101 and the tire widthwise outer ends 109a of the chafers 109. Reference numerals 102 and 108 denote bead cores and bead fillers, respectively. As the chafer, for example, a nylon chafer made of nylon can be used.

[0109] In a tire 120 shown in Fig. 12, an auxiliary reinforcing layer 114 is disposed adjacent to and near an outer end 119a in the tire width direction of a chafer 119 disposed on the outside of a carcass ply 111 in a bead portion, and is disposed so as to enclose the outer end 119a in the tire width direction from the outside in the tire radial direction, covering the outer and inner sides of the tire, and extending radially inward of the outer end 119a in the tire width direction. In this case, too, it is possible to obtain the effect of suppressing the occurrence of cracks from the outer end 119a in the tire width direction of the chafer 119. Reference numeral 112 denotes a bead core, and 118 denotes a bead filler.

[0110] In a tire 130 shown in Fig. 13, auxiliary reinforcing layers 124A, 124B are disposed adjacent to the vicinity of the cord cut ends 121a at the turned-up ends of two carcass plies 121 serving as main cord reinforcing layers, and are disposed in a position that covers the cord cut ends 121a from the outer side in the tire radial direction, wrapping around the cord cut ends 121a from the outer side in the tire radial direction, and covering the outer and inner sides of the tire, and extending radially inward of the cord cut ends 121a of the carcass ply 121. In this case, too, it is possible to obtain the effect of suppressing the occurrence of cracks from the cord cut ends 121a at the turned-up ends of the carcass ply 121. Note that reference numerals 122 and 128 indicate bead cores and bead fillers, respectively.

[0111] In a tire 140 shown in Fig. 14, auxiliary reinforcing layers 134A, 134B are disposed adjacent to and near cord cut ends 131a at the turned-up end of a carcass ply 131 serving as a main cord reinforcing layer and tire widthwise outer end portions 139a of chafers 139 disposed outside the carcass ply 131 in the bead portion, and are disposed in positions that enclose the cord cut ends 131a and tire widthwise outer end portions 139a from the tire radially outer side, covering the outer and inner sides of the tire, and extend radially inward of the cord cut ends 131a or tire widthwise outer end portions 139a of the carcass ply 131. This also provides the effect of suppressing cracks from occurring at the cord cut ends 131a at the turned-up end of the carcass ply 131 and the tire widthwise outer end portions 139a of the chafers 139. Reference numerals 132 and 138 denote bead cores and bead fillers, respectively.

[0112] In a tire 150 shown in Fig. 15, an auxiliary reinforcing layer 144 is disposed adjacent to and near an outer end 149a in the tire width direction of a chafer 149 disposed on the outside of a carcass ply 141 in the bead portion, and is disposed in a position that wraps around the outer end 149a in the tire width direction from the outside in the tire radial direction, covering the outer and inner sides of the tire, and extending radially inward of the outer end 149a in the tire width direction. In this case, too, it is possible to obtain the effect of suppressing cracks from occurring at the outer end 149a in the tire width direction of the chafer 149. Note that reference numeral 142 denotes a bead core, and 148 denotes a bead filler.

[0113] Fig. 16 is a schematic half-side cross-sectional view of a pneumatic tire according to one embodiment of the present invention. In a tire 160 shown in Fig. 16, a tread portion 161, a sidewall portion 162, and a bead portion 163 are reinforced by a single carcass ply 164 extending in a toroidal shape from one bead portion 163 to the other bead portion 163. The tread portion 161 is also reinforced by at least two belt layers (two layers, a first belt layer 165 and a second belt layer 166 in Fig. 16) disposed on the radially outer side of the crown region of the carcass ply 164. Note that the tire 160 shown in Fig. 16 may include a plurality of carcass plies 164.

[0114] In a tire 160 shown in Fig. 16, a first belt layer 165 is disposed radially outward of a crown region of a carcass ply 164, and a second belt layer 166 is disposed radially outward of the first belt layer 165. As shown in Fig. 16, the belt width (length in the tire width direction) of the second belt layer 166 is usually smaller than that of the first belt layer 165. The first belt layer 165 and the second belt layer 166 are sequentially laminated to form a belt 167. In the illustrated example, the belt 167 is made up of two belt layers 165, 166, but the belt 167 may be made up of three or more belt layers.

[0115] In the tire 160 shown in FIG. 16 , the thickness of the first belt layer 165 and the thickness of the second belt layer 166 at the tire center portion are preferably 1.00 mm or less. By setting the thickness of each belt layer at the tire center portion to 1.00 mm or less in this way, it is possible to reduce the weight of the tire and the rolling resistance. From the same viewpoint, the thickness of the first belt layer 165 at the tire center portion is more preferably 0.90 mm or less. Furthermore, the thickness of the second belt layer 166 at the tire center portion is more preferably 0.90 mm or less. To achieve such thicknesses, the diameters of the cords 165A, 166A embedded in the first belt layer 165 and the second belt layer 166, the coating thicknesses of the coating rubbers 165B, 166B, etc. can be appropriately selected. The tire center portion refers to the portion located within a distance of 1 / 4 of the tire contact width from the tire equatorial plane in the tire width direction.

[0116] Figure 17A shows a schematic cross-sectional view of an end (end in the tire width direction; the same applies below) of a belt 167 in a pneumatic tire according to one embodiment of the present invention, and Figure 17B shows a schematic cross-sectional view of the end of a belt 167 in a pneumatic tire according to another embodiment of the present invention. As shown in the figure, the first belt layer 165 and the second belt layer 166 are formed by embedding a plurality of cords (165A, 166A) in coating rubber (165B, 166B). More generally, these belt layers 165, 166 are formed by a rubber-cord composite in which parallel-wound cords (cords 165A, 166A) are covered with coating rubber (165B, 166B). The cords 165A, 166A may be formed of belt cords conventionally used in tires, such as steel or aramid fiber. A preferred example of the belt cord is a steel cord.

[0117] As shown in the figure, an auxiliary reinforcing layer 168 is arranged at the end of the belt 167, and more specifically, the auxiliary reinforcing layer 168 is arranged at least on the radially inner side of the first belt layer 165, between the first belt layer 165 and the second belt layer 166, and on the radially outer side of the second belt layer 166. By arranging the auxiliary reinforcing layer 168 at the end of the belt 167 in this manner, it is possible to improve durability at the belt end. The rubber on the radially inner side of the first belt layer 165 can improve durability in relation to components (e.g., carcass ply 164) arranged further radially inward in the tire, and the rubber on the radially outer side of the second belt layer 166 can improve durability in relation to components (e.g., belt reinforcing layer) that may be arranged further radially outward in the tire.

[0118] Furthermore, as shown in the figure, when the portion of the auxiliary reinforcing layer located on the inner side of the first belt layer 165 in the tire radial direction is defined as auxiliary reinforcing portion A (168A), the portion of the auxiliary reinforcing layer located between the first belt layer 165 and the second belt layer 166 is defined as auxiliary reinforcing portion B (168B), and the portion of the auxiliary reinforcing layer located on the outer side of the second belt layer 166 in the tire radial direction is defined as auxiliary reinforcing portion C (168C), the auxiliary reinforcing portion B (168B) has the longest length in the direction toward the tire center portion (which is roughly synonymous with "length in the tire width direction"). In other words, the lengths of the auxiliary reinforcing portion A (168A), auxiliary reinforcing portion B (168B), and auxiliary reinforcing portion C (168C) in the direction toward the tire center portion are respectively defined as L A , L B and L C (See Figure 17A) When A / L B is less than 1.0, and L C / L B is less than 1.0. In addition, as shown in the figure, among the auxiliary reinforcing portion A (168A), the auxiliary reinforcing portion B (168B), and the auxiliary reinforcing portion C (168C), the auxiliary reinforcing portion B (168B) is closest to the tire center portion.

[0119] The above-described mode of the auxiliary reinforcing layer 168 can typically be achieved by manufacturing a tire according to a manufacturing method for a pneumatic tire, which will be described later. In the manufacturing method for a pneumatic tire, as will be described later, gaps are unlikely to be formed between the first belt layer 165 and the second belt layer 166, and between the second belt layer 166 and a layer that may be disposed outside the second belt layer 166 (for example, a belt reinforcing layer), and this also contributes to improving durability at the belt end portions.

[0120] In the tire shown in FIGS. 17A and 17B, L A / L B is 0.5 or less, and L C / L B is 0.5 or less. In this case, the formation of gaps at the belt ends is further suppressed. A / L B is more preferably 0.4 or less, and LC / L B is more preferably 0.4 or less.

[0121] In the tire of Fig. 17A (and Figs. 16 and 18), the auxiliary reinforcing portions A, B and C are integrated as an auxiliary reinforcing layer 168 and arranged at the end of the belt 7, but such integration is not essential. For example, of the auxiliary reinforcing layer, a portion (auxiliary reinforcing portion A) on the inner side in the tire radial direction of the first belt layer 165, a portion (auxiliary reinforcing portion B) between the first belt layer 165 and the second belt layer 166, and a portion (auxiliary reinforcing portion C) on the outer side in the tire radial direction of the second belt layer 166 may be arranged separately. Also, as shown in Fig. 17B, the auxiliary reinforcing layer 168 (sheet) wrapping the end of the first belt layer 165 and the auxiliary reinforcing layer 168 (sheet) wrapping the end of the second belt layer 166 may be in contact with each other (without being completely integrated). However, from the viewpoint of further improving the durability of the belt end portion, it is preferable that the portions A, B, and C are integrated as the auxiliary reinforcing layer 168.

[0122] FIG. 18 is a schematic cross-sectional view of a tire center portion and an end portion of a belt 167 in a pneumatic tire according to one embodiment of the present invention. The end portion of the belt 167 in FIG. 18 corresponds to that shown in FIG. 17A. As shown in the figure, when the shortest distance between a cord 166A of the second belt layer 166 and a cord 165A of the first belt layer 165 in the tire center portion is a and the shortest distance between a cord 166A at the endmost portion of the second belt layer 166 and a cord 165A of the first belt layer 165 is b, b / a is 1.8 or more and 4.0 or less. In this way, by widening the spacing between the cords of the first belt layer 165 and the second belt layer 166 at the belt end portion, it is possible to suppress distortion that causes belt edge separation. In the tire shown in FIG. 18, by setting b / a to 1.8 or more, it is possible to improve durability at the belt end portion, particularly durability against belt edge separation. Furthermore, by setting b / a to 4.0 or less, it is possible to ensure the sufficiently low rolling resistance desired for a tire. From the same viewpoint, b / a is preferably 1.95 or more, more preferably 2.00 or more, and is preferably 3.90 or less. Note that the "shortest distance b between the cord at the extreme end of the second belt layer and the cord in the first belt layer" essentially represents the shortest distance between the cord at the extreme end of the second belt layer and the tangent line (dotted line in Fig. 18) of the multiple cords aligned in the first belt layer.

[0123] Fig. 19 is a schematic cross-sectional view of a center portion of a belt 167 in a pneumatic tire according to one embodiment of the present invention, which corresponds to the portion surrounded by the dashed line in Fig. 18. In the tire shown in Fig. 19, it is preferable that the distances between the interface of the first belt layer 165 and the cord 165A in the tire center portion (i.e., the distance c1 from the upper surface to the cord 165A and the distance c2 from the lower surface to the cord 165A) are both 0.14 mm or less, and the distances between the interface of the second belt layer 166 and the cord 166A in the tire center portion (i.e., the distance c3 from the upper surface to the cord 166A and the distance c4 from the lower surface to the cord 166A) are both 0.14 mm or less. By adopting such an embodiment, it is possible to more sufficiently improve the low rolling resistance of the tire. From the same viewpoint, the distance 165A between the interface and the cord of the first belt layer 165 and the distance 166A between the interface and the cord of the second belt layer 166 in the tire center portion are more preferably 0.13 mm or less, and further preferably 0.12 mm or less. As can be seen from FIGS. 18 and 19, the distance a shown in FIG. 18 is the distance (c4+c1) shown in FIG.

[0124] In the first belt layer 165 and the second belt layer 166 described above, the multiple cords embedded in the coating rubber can be arranged so as to be inclined at an angle of, for example, 15 to 40 degrees with respect to the tire circumferential direction. Furthermore, the carcass ply 164 can use cords extending in a direction substantially perpendicular to the tire circumferential direction, for example, at an angle of 70 to 90 degrees. Examples of cords for the carcass ply 164 include organic fiber cords or steel cords, which have traditionally been used in tire cords. Examples of preferred organic fibers include nylon fiber, polyester fiber, rayon fiber, polyethylene naphthalate fiber, and aramid fiber. Furthermore, a belt reinforcing layer (also referred to as a cap layer) may be disposed on the outer side of the belt 167 in the tire radial direction. In the tire 160 shown in FIG. 16 , a bead core 170 is embedded in each of a pair of bead portions 163, and the carcass ply 164 is folded back from the inside to the outside of the tire and secured around the bead core 170. However, the carcass ply 164 may be wound around the bead core 170 and secured (not shown), or may be sandwiched between bead wires from both sides and secured (not shown). A tread pattern may be formed on the surface of the tread portion 161. The tire 160 shown in FIG. 16 may also have an inner liner (not shown) formed as the innermost layer. The gas to be filled in the pneumatic tire of the present invention may be ordinary air or air with a modified oxygen partial pressure, or an inert gas such as nitrogen. The pneumatic tire of the present invention is suitable for use as a pneumatic tire for passenger cars.

[0125] The coating rubbers 165B, 166B used in the first and second belt layers are not particularly limited as long as they are a general rubber composition capable of coating the cords 165A, 166A. Examples of rubber components include diene rubbers, with natural rubber or isoprene rubber being particularly preferred. The coating rubbers 165B, 166B may contain fillers such as carbon black as long as the fillers do not affect the coating rubber's adhesiveness, durability, and other performance characteristics. HAF-class carbon black is preferred as the carbon black, and the carbon black content in the coating rubbers 165B, 166B may be 50 to 70 parts by mass per 100 parts by mass of the rubber component. The coating rubbers 165B, 166B may also contain, in addition to the above-mentioned components, crosslinking agents such as vulcanization accelerators, sulfur, and zinc oxide; adhesion promoters such as cobalt compounds containing cobalt salts; antioxidants; oils; resins; and the like. Examples of the antiaging agent include amine-based antiaging agents such as 6PPD, and bisphenol-based antiaging agents such as o-MBp14. These antiaging agents may be used alone or in combination of two or more.

[0126] In the first belt layer 165 and the second belt layer 166 described above, typically, a plurality of cords 165A, 166A are arranged in parallel. These cords 165A, 166A are generally steel cords. The structure of these cords is not particularly limited. However, from the viewpoint of effectively achieving both improved tire durability and reduced rolling resistance, the structure of the cords does not need to be particularly limited, and may be arbitrarily selected from a monofilament structure, a single-twist structure such as 1×N (N: 2 to 7), a multi-twist structure such as K+N (K: = 1 to 2, N: 2 to 8), or a multi-twist structure. The tires used in the examples and comparative examples of this specification used tire cords with a single-twist structure of 1×N (N = 5). From the same viewpoint, it is also preferable that the cords are monofilaments arranged in parallel without being twisted together. In the case of the 1×N structure, the cord may have a 1×N open structure in which the filaments are twisted together without touching each other and spaced apart. A cord with an open structure has better fatigue resistance than a cord in which the filaments are twisted together while touching each other. The 1xN open structure cord may be formed by sandwiching unvulcanized rubber between filaments and twisting them together, or by coating the surfaces of the filaments with unvulcanized rubber and then twisting them together. Alternatively, the filaments may be shaped before twisting. When shaped beforehand, the filaments are preferably shaped at a pitch ranging from 8 mm to 16 mm. A shaping pitch within this range enhances rubber permeability and further improves durability. Furthermore, the ratio Sf / Sc of the filament cross-sectional area Sf in the cord cross section to the area Sc of the circumscribed circle of the cord cross section is preferably in the range of 0.4 to 0.7. If Sf / Sc is in this range, rubber permeability is improved, and durability can be further improved. The filaments constituting the cords 165A and 166A may be subjected to a surface treatment during drawing. In this case, the amount of phosphoric acid on the surface of the filament after the surface treatment is 2.0 mg / m 2 The amount of phosphoric acid on the surface of the filament is preferably 2.0 mg / m or less. 2 If it is below this, the adhesive strength between the filament and the coating rubber will be good.

[0127] The filaments constituting the cords 165A, 166A used in the first belt layer 165 and the second belt layer 166 are preferably classified as ST grade (super tensile strength cord) or UT grade (ultra tensile strength cord) as defined in ISO 17832:2009, and are particularly preferably classified as UT grade. In this case, it is possible to effectively achieve both improved tire durability and low rolling resistance. From the same viewpoint, when the diameter of the filament constituting the cord is X (mm) and the tensile strength of the filament is Y (MPa), the cords 165A and 166A satisfy the following formula (1): 4250-2000X≦Y≦4500-2000X (1) It is preferable that the following is satisfied. In the filaments constituting the cords 165A and 166A, from the viewpoint of fatigue resistance, the hardness of the surface layer is preferably 90 to 110%, and more preferably 100%, of the hardness of the inner layer. Here, the surface layer of the filament refers to the layer (region) from the outermost surface of the filament to a depth of 0.01 mm, and the inner layer of the filament refers to the layer (region) inside the surface layer. The hardness can be measured, for example, as Vickers hardness. The hardness of the surface layer of the filament can be measured at a depth of 0.005 mm from the outermost surface of the filament, and the hardness of the inner layer of the filament can be measured in a region deeper than 0.04 mm from the outermost surface of the filament. There is no particular limitation on the method for producing the filaments constituting the cords 165A and 166A. For example, the filaments may be obtained by refining iron ore and wiredrawing, by refining scrap iron and wiredrawing, or by recycling steel extracted from tires.

[0128] In the first belt layer 165 and the second belt layer 166, the end density of the cords 165A, 166A is preferably 50 pieces / dm or more and 250 pieces / dm or less. In this case, it is possible to effectively achieve both improved tire durability and low rolling resistance. In particular, when the cords have a 1×N structure (N is an integer selected from 2 to 6), the end density of the cords is preferably 60 pieces / dm or more and 95 pieces / dm or less. On the other hand, when the cords are monofilaments, the end density of the cords is preferably 180 pieces / dm or more and 240 pieces / dm or less.

[0129] The diameter of the cords 165A, 166A used in the first belt layer 165 and the second belt layer 166 is preferably 0.2 mm or more and 1.2 mm or less. In this case, it is possible to effectively achieve both improved tire durability and low rolling resistance. In particular, when the cords have a 1×N structure (N is an integer selected from 2 to 6), the diameter of the cords is preferably 0.4 mm or more and 1.2 mm or less, and more preferably 0.5 mm or more and 1.0 mm or less. On the other hand, when the cords are monofilaments, the diameter of the cords is preferably 0.24 mm or more and 0.28 mm or less.

[0130] (Application) The pneumatic tire of the present embodiment described above can be applied to various vehicles, and can be used as a tire for passenger cars, a tire for trucks, a tire for light trucks, and a tire for large vehicles, for example.

[0131] <Manufacturing method of pneumatic tires> In the present invention, the auxiliary reinforcing layer containing the copolymer having conjugated diene units and non-conjugated olefin units can be produced by any method. For example, first, a sheet containing the copolymer having conjugated diene units and non-conjugated olefin units is produced (sheet production step). The thickness of this sheet is preferably 0.5 mm to 1.5 mm. The copolymer-containing sheet may be produced by using the copolymer as is, or by mixing any additive components in addition to the copolymer. Alternatively, the copolymer may be produced by kneading the copolymer alone or together with any other additive components using a kneader such as a single-screw extrusion kneader, a twin-screw extrusion kneader, a Banbury mixer, a roll, or an internal mixer. The kneading of the components may be carried out in one stage or in two or more stages. When a sheet containing the copolymer is formed from a composition containing the copolymer and other optional additive components, the composition may contain, in addition to the copolymer, the above-mentioned olefin resin, rubber component, filler, silane coupling agent, antioxidant, softener, crosslinking agent, crosslinking accelerator, etc. Here, the content of the copolymer in the composition is not particularly limited, but is preferably 50% by mass or more.

[0132] When the components of the composition are melt-kneaded in an extrusion kneader and the composition is extruded, the extruded composition may be directly cut into pellets, or the extruded composition may be formed into strands and then cut into pellets using a pelletizer. The pellets may have common shapes such as cylindrical, prismatic, and spherical shapes.

[0133] The sheet containing the copolymer may be produced by melt-kneading the composition and then extruding the composition, or by hot-pressing the composition. The heat pressing temperature is preferably 120 to 160°C, and more preferably 130 to 150°C.

[0134] Next, the obtained sheet containing the copolymer is cut, for example, at intervals of 20 to 1000 mm, and the cut sheets are joined sequentially to obtain strips containing the copolymer (cutting step). In the sheet preparation step, a sheet having a thickness of 0.07 to 5 mm is prepared, and in the cutting step, the obtained sheet is cut at intervals of 20 to 1000 mm, which makes it easy to form an auxiliary reinforcing layer having a desired shape and thickness.

[0135] Next, when the auxiliary reinforcing layer is arranged adjacent to the cut cord end of the carcass ply, in the primary molding of the green tire, the obtained strip containing the copolymer is attached adjacent to the vicinity of the cut cord end of the carcass ply, which is the carcass folded portion in the cylindrical molded body of the carcass ply, so as to cover at least the cut cord end from the outside of the tire over the entire circumference (attaching process).

[0136] Next, in the secondary molding of the green tire, the strip containing the copolymer is expanded together with the carcass ply to a predetermined outer diameter (expansion step) to produce a molded green tire.

[0137] Furthermore, when the auxiliary reinforcing layer is disposed adjacent to the cut end of the cord of the belt layer, there is no particular limitation, but for example, in the secondary molding of the green tire, a strip containing the copolymer is attached and disposed adjacent to the vicinity of the cut end of the cord of the belt layer, and then a rubber composition that will become the tread portion is coated thereon, thereby manufacturing a molded green tire. Furthermore, when the auxiliary reinforcing layer is disposed adjacent to the outer end of the chafer in the tire width direction, it can be done in a similar manner.

[0138] The green tire obtained as described above is vulcanized in accordance with a conventional method at a vulcanization temperature of 140°C to 190°C for 3 to 50 minutes (vulcanization step), thereby producing a pneumatic tire that has improved durability and is also lightweight.

[0139] (Manufacturing method of the tire shown in Figure 16) 16 preferably includes a step (lamination step) of laminating the first belt layer 165 and the second belt layer 166. Furthermore, in the manufacturing method, prior to the lamination step, an end of the first belt layer 165 is wrapped with a first sheet 168 containing a copolymer having a conjugated diene unit and a non-conjugated olefin unit, and an end of the second belt layer 166 is wrapped with a second sheet 8 containing a copolymer having a conjugated diene unit and a non-conjugated olefin unit, and at that time, it is preferable that the end of each belt layer is wrapped with a shift such that the length of the sheet portion located on the side facing the other belt layer when laminated is longer than the length of the sheet portion located on the opposite side for both the first sheet 168 and the second sheet 168. According to this manufacturing method, it is possible to manufacture the tire shown in FIG. 16 while effectively suppressing the formation of gaps between the first belt layer 165 and the second belt layer 166, and between the second belt layer 166 and a layer that may be arranged outside the second belt layer 166 (for example, a belt reinforcing layer).

[0140] Fig. 20A is a schematic view showing a lamination step in a manufacturing method of a pneumatic tire according to one embodiment of the present invention, and Fig. 20B is a schematic cross-sectional view of an end portion of a belt in a pneumatic tire obtained according to the manufacturing method of Fig. 20A. As shown in the figure, in the lamination process, for example, a first belt layer 165, a second belt layer 166, and other layers 176 (belt reinforcing layer, rubber layer, crimping layer, etc.) are laminated in this order, and a roll 175 is pressed from above and moved from the tire center toward the end of each layer to crimp the first belt layer 165, the second belt layer 166, and other layers 176. At this time, the end of the first belt layer 165 is wrapped in a first sheet 168 in advance, and the end of the second belt layer 166 is wrapped in a second sheet 168. At this time, the first sheet 168 wrapping the end of the first belt layer 165 has a length (length in the tire width direction, the same applies hereinafter) (L B1 ') is the length of the sheet part on the opposite side (L AThe second sheet 168 wrapping the end of the second belt layer 166 is offset so that the length (L ′) of the sheet portion located on the side facing the first belt layer 165 when the layers are laminated is longer than the length (L ′) of the second sheet 168. B2 ') is the length of the sheet part on the opposite side (L c The sheet 168 is offset so as to be longer than the end of the first belt layer 165 and the end of the second belt layer 166, and wraps around the end of the second belt layer 166. When lamination and pressure bonding are performed in such an arrangement of the sheet 168, gaps are unlikely to be formed at the belt end between the first belt layer 165 and the second belt layer 166, and between the second belt layer 166 and the other layer 176, as schematically shown in Fig. 20B.

[0141] On the other hand, Fig. 21A is a schematic view showing a part of a conventional method for manufacturing a pneumatic tire, and Fig. 22B is a schematic cross-sectional view of an end portion of a belt in a pneumatic tire obtained according to the manufacturing method of Fig. 21A. Conventionally, as shown in FIG. 21A, the first sheet 168 that wraps the end of the first belt layer 165 and the second sheet 168 that wraps the end of the second belt layer 166 are both wrapped symmetrically around the end (i.e., L A '≒L B1 ', L B2 '≒L C When lamination and pressure bonding are performed in such an arrangement of the sheet 168, the first belt layer 165, the second belt layer 166, and the other layer 176 cannot be deformed until they are in close contact with each other, and as a result, large gaps (air pockets) tend to form at the belt ends between the first belt layer 165 and the second belt layer 166, and between the second belt layer 166 and the other layer 176, as shown in Fig. 21B.

[0142] The other layer 176 may be a tire component such as a belt reinforcing layer or a rubber layer. On the other hand, if the other layer 176 is not a tire component, the other layer 176 may be peeled off as appropriate after the lamination step.

[0143] The first and second sheets may be, for example, rectangular sheets.

[0144] In the laminating step, it is preferable to laminate the first belt layer 165 and the second belt layer 166 so that the first sheet 168 and the second sheet 168 are in contact with each other.

[0145] In the manufacturing method of this embodiment, when the first belt layer 165 and the second belt layer 166 are laminated, it is preferable that the end of the first sheet 168 located between the first belt layer 165 and the second belt layer 166 does not overlap with the end of the second sheet 168. In other words, the distance L between the end of the first sheet 168 located between the first belt layer 165 and the second belt layer 166 and the end of the second sheet 168 is x It is preferable that ' (distance in the tire width direction) (see FIG. 20A) exceeds 0. This can further suppress the formation of gaps at the belt ends. In this case, the terminal end of the first sheet 168 of the first belt layer 165 may be closer to the tire center portion, or the terminal end of the second sheet 168 of the second belt layer 166 may be closer to the tire center portion as shown in FIG. 20A. However, from the viewpoint of more effective suppression of gap formation, it is more preferable that the terminal end of the second sheet 168 of the second belt layer 166 is closer to the tire center portion as shown in FIG. 20A.

[0146] In the manufacturing method of this embodiment, as long as the arrangement of the sheet 168 around the first belt layer 165 and the second belt layer 166 is as described above and the tire configuration shown in FIG. 16 is obtained, other specific manufacturing conditions are not particularly limited. For example, the lengths (L A , L B and L C ) and the relative positional relationship are determined by the length (L A ', L B1 '~L B2 ', L C'), a person skilled in the art can make appropriate adjustments taking this into consideration. Furthermore, for example, in order to adjust the spacing between the cords of the first belt layer 165 and the second belt layer 166 (and thus to set b / a to 1.8 or more and 4.0 or less), for example, the thickness of the first sheet 168 wrapping the end of the first belt layer 165 and / or the thickness of the second sheet 168 wrapping the end of the second belt layer 166 can be appropriately adjusted. [Example]

[0147] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.

[0148] <Synthesis of ethylene-styrene-butadiene copolymer (ESB)> Ethylene-styrene-butadiene copolymers (ESB)-1 and 2 were produced in accordance with the method described in the section "Preparation of Second Copolymer" of WO 2021 / 075131, by varying the ratio of the raw materials ethylene, styrene, and butadiene, the amount of catalyst used, the reaction temperature, and the reaction time.

[0149] <Method for measuring copolymer properties> The following physical properties of the resulting ESB-1 and ESB-2 were measured, and the results are shown in Table 1.

[0150] (1) Content of ethylene units, styrene units, and butadiene units The contents (mass%, mol%) of ethylene units, styrene units, and butadiene units in the copolymer are 1 The ratio was calculated from the integral ratio of each peak in the H-NMR spectrum (100°C, d-tetrachloroethane standard: 6 ppm).

[0151] (2) Number average molecular weight (Mn), weight average molecular weight (Mw), and molecular weight distribution (Mw / Mn) Gel permeation chromatography [GPC: HLC-8121GPC / HT manufactured by Tosoh Corporation, column: GMH manufactured by Tosoh Corporation] HRThe number average molecular weight (Mn), weight average molecular weight (Mw), and molecular weight distribution (Mw / Mn) of the copolymer in terms of polystyrene were determined using a differential refractometer (RI) with monodisperse polystyrene as the standard. The measurement temperature was 40°C.

[0152] (3) Melting point (Tm) The melting point (Tm) of the copolymer was measured using a differential scanning calorimeter (DSC, manufactured by TA Instruments Japan, "DSCQ2000") in accordance with JIS K 7121-1987.

[0153] (4) Tensile strength (Tb) and elongation at break (Eb) The specimens were molded into a dumbbell shape No. 3 according to JIS K 6251 (2017) and used as test pieces. The tensile strength (Tb) was measured based on JIS K 6251 (2017) using a tensile testing device (manufactured by Instron) by elongating the test piece by 100% at 25°C, and the maximum tensile force required to break the test piece was measured. The elongation at break (Eb) was determined by measuring the length of the test piece when it broke after pulling it at a rate of 100 mm / min at 25° C., and calculating the ratio of this length to the length before pulling (100%).

[0154] (5) Confirmation of main chain structure Regarding the synthesized copolymer, 13 Measure the C-NMR spectrum 13 In the C-NMR spectrum chart, no peaks were observed between 10 and 24 ppm, confirming that the main chain of the synthesized copolymer was composed solely of an acyclic structure.

[0155] [Table 1]

[0156] <Production of Ethylene-Styrene-Butadiene Copolymer (ESB) Sheets> Each ESB was extruded into a film approximately 0.1 mm thick to produce an ESB sheet. The actual thickness of each ESB sheet is shown in Table 2.

[0157] <Rubber sheet manufacturing> An unvulcanized rubber composition was prepared and rolled into a sheet with a target thickness of 0.5 mm, 0.3 mm, or 0.1 mm to produce rubber sheets 1 to 4. The measured thickness of each rubber sheet is shown in Table 2.

[0158] When the unvulcanized rubber composition was rolled into a sheet with a target thickness of 0.1 mm, the unvulcanized rubber composition stuck to the roll during sheeting, and when peeled off from the roll, the sheet (film) shape was deformed and broke, making it impossible to produce a rubber sheet. In addition, to prevent the unvulcanized rubber composition from sticking to the roll, the unvulcanized rubber composition was sandwiched between two PET films and rolled to a target thickness of 0.1 mm. However, even in this case, when the unvulcanized rubber composition was peeled off from the PET film, the sheet (film) shape was deformed and broke, so a rubber sheet could not be produced.

[0159] [Table 2]

[0160] The produced ESB Sheet 1, ESB Sheet 2 and Rubber Sheet 1 were tested for adhesion and creep properties by the following methods.

[0161] (6) Adhesion test of sheet (unvulcanized) The produced ESB sheet 1, ESB sheet 2 and rubber sheet 1 were cut into pieces measuring 90 mm in length and 20 mm in width. Each cut sheet was folded at a position 20 mm from the end in the length direction. Each folded sheet is pressed under a pressure of 2gr / cm 2 It was pressed. One end of each pressed sheet was hung with a clamp (fixing tool) to check whether the folded part would unfold under the sheet's own weight. The results are shown in Table 3.

[0162] [Table 3]

[0163] (Result discussion) The results of the adhesion test showed that the sheet made of ESB had less adhesion in the unvulcanized state than rubber sheets. Sheets made of ESB have little adhesion to each other or to supports or rolls to which the sheets are attached, and they maintain their sheet-like shape, allowing the surface to be peeled off by folding it open, etc.

[0164] Generally, in order to place a sheet-like material at a desired location on a tire, if the sheets are sticking to each other or to a support, they must be peeled off and returned to their sheet form. Unlike conventional rubber sheets, the adhesive on the ESB sheet's surface peels off under its own weight when it comes into contact with the material, so there is almost no peeling force generated when peeling, and the sheet does not deform. Unvulcanized rubber sheets used in tire manufacturing contain conjugated dienes that crosslink during vulcanization, resulting in the adhesive properties characteristic of rubber. ESB sheets also contain conjugated dienes, which can be crosslinked during vulcanization, allowing them to be used in rubber components that become part of tires. Furthermore, ESB sheets can keep the peeling force due to the adhesiveness of the sheet surface low. In particular, ESB sheeting with a sheet thickness of 0.1 mm has low adhesiveness, which is thought to be why it adheres less to rolls and supports.

[0165] (7) Creep test of sheet (unvulcanized) Sheet samples (90 mm long, 20 mm wide) were prepared in the same manner as in the adhesive test described above. ESB Sheet 1, ESB Sheet 2, Rubber Sheet 1, and Rubber Sheet 2 were used as samples for the creep test. Two marks were made in the center of each sheet sample, spaced 5 cm apart. Each sheet sample was clamped at one end with a clamp and at the other end with another clamp, and a static load of 70 g (weight of the clamp plus any additional load) was applied, with the clamp spacing set at 8 cm. After applying the load and maintaining it for 5 minutes, the distance between the marked lines was measured and the creep property was evaluated according to the following formula. The results are shown in Table 4. Creep resistance = (gage mark spacing after loading, cm) / 5 cm x 100 (%)

[0166] [Table 4]

[0167] (Result discussion) The results of the creep test on the sheet showed that the creep property of the sheet made of ESB in the unvulcanized state was smaller than that of the rubber sheet, and that creep deformation due to the input of external stress was smaller. In particular, the ESB sheet, which is approximately 0.1 mm thick, is thinner than a rubber sheet, which is approximately 0.5 mm thick, but has less elongation, and can be used without problems in tire manufacturing. On the other hand, a rubber sheet with a thickness of approximately 0.3 mm stretches under load, causing deformation during tire manufacturing, and it is clear that it cannot be used stably in the desired position and thickness for the desired components.

[0168] From the above results, it is clear that by using a copolymer having conjugated diene units and non-conjugated olefin units, the auxiliary reinforcing layer can be made thinner during molding of a green tire, which is a means of reducing the tire weight.

[0169] <Tire manufacturing> (Manufacturing ribbon-shaped ESB sheets and ribbon-shaped rubber sheets) The ESB sheet 1 was slit into a ribbon having a width of 25 mm, and then cut into a length of 1610 mm. The rubber sheet 1 was also slit into ribbons with a width of 25 mm and cut into strips with a length of 1610 mm. The rubber sheet 4 was slit into ribbons with a width of 50 mm and cut into ribbons with a length of 1610 mm. The masses of the obtained ribbon-shaped ESB sheet 1, ribbon-shaped rubber sheet 1, and ribbon-shaped rubber sheet 4 were measured. The results are shown in Table 5.

[0170] [Table 5]

[0171] (Production of test tires) As a test tire, a test tire was manufactured by applying an ESB sheet or a rubber sheet to a tire having a tire size of 155 / 65R14 (length of the first belt layer in the tire width direction: 120 mm, length of the second belt layer in the tire width direction: 110 mm).

[0172] (Production of tire of Example 1) In the secondary molding of the green tire, an ESB sheet 1 having a width of 25 mm was arranged along the first belt layer over the entire circumference of the tire, on the radially outer side of the first belt layer, so as to extend from a position 39 mm outward in the tire width direction from the tire equatorial plane to the outer side in the tire width direction. Specifically, on a tire building drum, which is a cylindrical mold, the ESB sheet 1 was attached over the entire circumference of the first belt layer in both end regions of the first belt layer, starting from a position equivalent to 39 mm outward in the tire width direction from the tire equatorial plane, so that the ESB sheet 1 was arranged over a position equivalent to 64 mm outward in the tire width direction from the tire equatorial plane. Next, other tire components such as the second belt layer were attached to the radially outer side of the first belt layer to form a green tire, which was then vulcanized at 186°C for 10 minutes to produce a test tire of Example 1.

[0173] (Production of tire of Example 2) In the secondary molding of the green tire, an ESB sheet 1 having a width of 25 mm was placed around the entire circumference of the tire, radially outside the first belt layer, extending from a position 39 mm outward in the tire width direction from the tire equatorial plane to the outside in the tire width direction. Next, the second belt layer was arranged on the outer side in the tire radial direction of the first belt layer, and then the ESB sheet 1 was folded outward in the tire radial direction from a position 55 mm outward in the tire width direction from the tire equatorial plane, and further folded inward in the tire width direction along the edge of the second belt layer, and a part of the ESB sheet 1 was attached to the outer surface in the tire radial direction of the second belt layer (i.e., the end portion in the width direction of the second belt layer was wrapped with the ESB sheet 1). Thereafter, other tire components were attached to form a green tire, and then vulcanization was performed at 186°C for 10 minutes to produce a test tire of Example 2.

[0174] (Tire manufacturing of Comparative Example 1) In the secondary molding of the green tire, a rubber sheet 1 having a width of 25 mm was arranged around the entire circumference of the tire, along the first belt layer, so as to extend radially outward from the first belt layer and 39 mm outward from the tire equatorial plane in the tire width direction. Next, other tire components such as the second belt layer were attached to the radially outer side of the first belt layer to form a green tire, which was then vulcanized at 186°C for 10 minutes to produce a test tire of Comparative Example 1.

[0175] (Tire manufacturing of Comparative Example 2) In the primary molding of the green tire, a 50 mm wide rubber sheet 4 was attached in advance to a width of 25 mm from the end of the second belt layer so as to wrap around the upper and lower surfaces of the second belt layer, to prepare a composite of the second belt layer and the rubber sheet 4. The composite of the second belt layer and the rubber sheet 4 was placed radially outside the first belt layer. Next, other tire components were attached to the radially outer side of the second belt layer to form a green tire, which was then vulcanized at 186° C. for 10 minutes to prepare a sample tire of Comparative Example 2.

[0176] (Measurement of tire weight) The weights of the obtained test tires (tire size: 155 / 65R14) of Examples 1 and 2 and Comparative Examples 1 and 2 were measured, and the results are shown in Table 6. The differential control for Example 1 is Comparative Example 1, and the differential control for Example 2 is Comparative Example 2.

[0177] [Table 6]

[0178] (Consideration) From the comparison between Comparative Example 1 and Example 1, and the comparison between Comparative Example 2 and Example 2 in Table 6, it can be seen that the ESB sheet of the Example has less sheet elongation, and therefore the sheet thickness can be made thinner, and in turn, the weight of the tire can be reduced by making the auxiliary reinforcing layer (sheet member) thinner.

[0179] As is clear from Patent Document 1 and the like, providing an auxiliary reinforcing layer is expected to improve durability, and therefore, according to the present invention, an auxiliary reinforcing layer containing a copolymer having conjugated diene units and non-conjugated olefin units is disposed adjacent to the vicinity of the cord cut end of at least one layer of the carcass ply and belt layer as the main cord reinforcing layer, or adjacent to the vicinity of the outer end in the tire width direction of the chafer arranged outside the carcass ply in the bead portion, thereby making it possible to improve tire durability and reduce the tire weight.

[0180] [Contribution to the United Nations-led Sustainable Development Goals (SDGs)] The SDGs have been proposed to realize a sustainable society. One embodiment of the present invention is thought to be a technology that can contribute to the achievement of goals such as "No. 7 - Affordable and clean energy for all," "No. 12 - Responsible consumption and production," and "No. 13 - Take urgent action against climate change." [Explanation of symbols]

[0181] 1,11,21,31,41,51,61,71,81,91,101,111,121,131,141,164: Carcass ply 1a, 11a, 21a, 33a, 43a, 51a, 63a, 73a, 83a, 91a, 101a, 121a, 131a: Cord cut end 2,12,22,52,92,102,112,122,132,142,170: Bead core 3, 33, 43, 63, 73, 83, 101, 111: Belt layer 4, 14A, 14B, 24, 34A, 34B, 44, 54, 64, 74, 84, 94A, 94B, 104A, 104B, 114, 124A, 124B, 134A, 134B, 144: Auxiliary reinforcement layer 5,95,163: Bead section 6,96,162:Sidewall 7,97,161: Tread section 8,18,28,58,98,108,118,128,138,148: Bead filler 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160: Pneumatic tires 109, 119, 139, 149: Chafer 109a, 119a, 139a, 149a: outer end of chafer in the tire width direction 165: First belt layer 166: Second belt layer 165A, 166A: Code 165B, 166B: Coated rubber 167: Belt 168: Auxiliary reinforcing layer (sheet) 168A: Auxiliary reinforcement part A 168B: Auxiliary reinforcement part B 168C: Auxiliary reinforcement part C 175: Roll 176:Other layers

Claims

1. A pneumatic tire comprising one or more carcass plies each having cut cords arranged in parallel, the side portions of which are wound around a bead core to form a toroidal shape, and one or more belt layers each having cut cords arranged in parallel are arranged on the radially outer side of a crown portion of the carcass ply, An auxiliary reinforcing layer is disposed adjacent to the vicinity of a cut end of a cord of at least one of the carcass ply and the belt layer as a main cord reinforcing layer, or adjacent to the vicinity of an outer end in the tire width direction of a chafer disposed on the outer side of the carcass ply in a bead portion, and the auxiliary reinforcing layer is disposed at a position covering at least the cut end of the cord of the adjacent main cord reinforcing layer or the vicinity of the outer end in the tire width direction of the chafer from the inner side and / or the outer side of the tire, A pneumatic tire, wherein the auxiliary reinforcing layer contains a copolymer having conjugated diene units and non-conjugated olefin units.

2. The pneumatic tire according to claim 1, wherein the copolymer has a melting point of 50 to 120°C.

3. The pneumatic tire according to claim 1, wherein the copolymer has a content of the conjugated diene units of more than 0 mol % and not more than 50 mol %, and a content of the non-conjugated olefin units of not less than 50 mol % and less than 100 mol %.

4. The pneumatic tire of claim 1 , wherein the copolymer further comprises an aromatic vinyl unit.

5. a first belt layer disposed on the radially outer side of the crown portion of the carcass ply and including cut cords arranged in parallel; a second belt layer disposed radially outward of the first belt layer and including cut cords arranged in parallel, The first belt layer and the second belt layer are each formed by embedding a plurality of cords in a coating rubber, a thickness of the first belt layer and a thickness of the second belt layer in a tire center portion are each 1.00 mm or less; where a is the shortest distance between a cord of the second belt layer and a cord of the first belt layer in the tire center portion, and b is the shortest distance between a cord at an end of the second belt layer and a cord of the first belt layer, b / a is 1.8 or more and 4.0 or less, the auxiliary reinforcing layer is disposed at the end portions of the first belt layer and the second belt layer, on the inner side in the tire radial direction of the first belt layer, between the first belt layer and the second belt layer, and on the outer side in the tire radial direction of the second belt layer; 2. The pneumatic tire according to claim 1, wherein when a portion of the auxiliary reinforcing layer located on the radially inner side of the first belt layer is defined as an auxiliary reinforcing portion A, a portion of the auxiliary reinforcing layer located between the first belt layer and the second belt layer is defined as an auxiliary reinforcing portion B, and a portion of the auxiliary reinforcing layer located on the radially outer side of the second belt layer is defined as an auxiliary reinforcing portion C, the auxiliary reinforcing portion B has the longest length in a direction toward the center portion and is closest to the tire center portion.

6. The lengths of the auxiliary reinforcing portions A, B, and C in the direction toward the tire center portion are respectively L Ａ , L Ｂ and L Ｃ When this is done, L Ａ / L Ｂ is 0.5 or less, and L Ｃ / L Ｂ The pneumatic tire according to claim 5, wherein the ρ is 0.5 or less.

7. 7. The pneumatic tire according to claim 5, wherein, in a tire center portion, a distance between the interface and the cords of the first belt layer and a distance between the interface and the cords of the second belt layer are both 0.14 mm or less.

8. The pneumatic tire according to claim 1 , wherein the auxiliary reinforcing layer is disposed near a cut end of a cord of at least one of the belt layers.

9. A method for manufacturing a pneumatic tire according to claim 1, a sheet-making step of making a sheet comprising a copolymer having conjugated diene units and non-conjugated olefin units; a cutting step of cutting the obtained sheet into strips; an attaching step of attaching the strip obtained in the primary molding of the green tire adjacent to the vicinity of the cord cut ends of the carcass ply, which is the carcass folded-up portion of the cylindrical molded body of the carcass ply, so as to cover at least the cord cut ends from the outer side of the tire over the entire circumference; and an expansion step of expanding the strip together with the carcass ply to a predetermined outer diameter in secondary molding of the green tire.

10. In the sheet preparation step, a sheet having a thickness of 0.07 to 5 mm is prepared, The method for manufacturing a pneumatic tire according to claim 9, wherein the obtained sheet is cut at intervals of 20 to 1000 mm in the cutting step.

11. A method for manufacturing a pneumatic tire according to claim 5, a lamination step of laminating the first belt layer and the second belt layer, a method for manufacturing a pneumatic tire, characterized in that, prior to the lamination step, an end portion of the first belt layer is wrapped with a first sheet containing a copolymer having a conjugated diene unit and a non-conjugated olefin unit, and an end portion of the second belt layer is wrapped with a second sheet containing a copolymer having a conjugated diene unit and a non-conjugated olefin unit, and at that time, for both the first sheet and the second sheet, the end portions of the belt layers are wrapped with a shift so that a length of a sheet portion located on a side facing the other belt layer when laminated is longer than a length of a sheet portion located on the opposite side.

12. 12. The method for manufacturing a pneumatic tire according to claim 11, wherein, when the first belt layer and the second belt layer are laminated together, an end of the first sheet and an end of the second sheet located between the first belt layer and the second belt layer do not overlap each other.

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