Pneumatic tire and manufacturing method for the same

Abstract

To provide a pneumatic tire that enables a sealant layer to exert puncture-sealing performance and can improve high-speed durability, and a manufacturing method for the same.SOLUTION: A pneumatic tire comprises a tread part 1 in an annular shape extending in a tire circumferential direction, a pair of side wall parts 2 arranged at both sides of the tread part 1, and a pair of bead parts 3 arranged inside in a tire radial direction of the side wall parts 2, in which at least one carcass layer 4 is hung between the pair of bead parts 3, a plurality of belt layers 7 are arranged at an outer periphery side of the carcass layer 4 in the tread part 1, and side reinforcement layers 11 having a crescent-shaped cross section are arranged inside in a tire width direction of the carcass layer 4 in the side wall parts 2. A sealant layer 20 is formed on an inner surface Ts of the tire in the tread part 1, and sealant of the sealant layer 20 is composed of silicone-based compositions.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a pneumatic tire having a sealant layer on the inner surface of the tire in the tread portion, and a manufacturing method thereof. More specifically, the present invention relates to a pneumatic tire that exhibits puncture sealing properties due to the sealant layer and is capable of improving high-speed durability, and a manufacturing method thereof. [Background technology]

[0002] Pneumatic tires with puncture sealing properties have been proposed that have a sealant layer made of an adhesive sealant on the inner surface of the tire tread (for example, Patent Document 1). In pneumatic tires with such a sealant layer, when a foreign object such as a nail penetrates the tread, the adhesive sealant clings to the foreign object and, as the foreign object falls off, is guided to the puncture hole, thereby providing a sealing effect.

[0003] Such conventional sealants are often made of butyl rubber. However, when using a butyl rubber sealant, a high temperature must be set when applying it, which causes further vulcanization in the tread, resulting in a problem of reduced high-speed durability. In particular, in the case of run-flat tires, the sidewalls are thickened by the side reinforcing layers, making the sidewalls the rate-limiting part during vulcanization. However, since the vulcanization time is longer than that of normal tires, the over-vulcanization of the tread significantly reduces high-speed durability. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-080909 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a pneumatic tire that exhibits puncture sealing properties due to a sealant layer and also enables improvement in high-speed durability, and a method for manufacturing the same. [Means for solving the problem]

[0006] In order to achieve the above object, the pneumatic tire of the present invention comprises a tread portion extending circumferentially of the tire to form an annular shape, a pair of sidewall portions arranged on either side of the tread portion, and a pair of bead portions arranged radially inward of the sidewall portions, with at least one carcass layer mounted between the pair of bead portions, with multiple belt layers arranged on the outer circumferential side of the carcass layer in the tread portion, and a side reinforcing layer with a crescent cross section arranged on the inner side of the carcass layer in the sidewall portions in the tire width direction, wherein a sealant layer is formed on the inner surface of the tire in the tread portion, and the sealant in the sealant layer is composed of a silicone-based composition.

[0007] Furthermore, the method for manufacturing a pneumatic tire of the present invention is a method for manufacturing the above-mentioned pneumatic tire, characterized in that after manufacturing the pneumatic tire excluding the sealant layer, when applying a sealant to the inner surface of the tire in the tread portion to form the sealant layer, the temperature of the sealant applied to the inner surface of the tire is set to 70°C or less. [Effects of the Invention]

[0008] In the present invention, in a pneumatic tire having a side reinforcing layer disposed in the sidewall portion, the sealant constituting the sealant layer is composed of a silicone-based composition, so the tire does not become hot when applied, as occurs with conventional sealants made of butyl-based rubber, and therefore the tread portion can be prevented from becoming over-vulcanized, and high-speed durability can be improved while the puncture sealing properties of the sealant layer are maintained.

[0009] In the pneumatic tire of the present invention, it is preferable that the end of the side reinforcing layer is disposed inward in the tire width direction from the end of the belt layer, and the end of the sealant layer is disposed outward in the tire width direction from the end of the side reinforcing layer. This allows the side reinforcing layer to reduce the amount of air leakage, thereby ensuring sufficient puncture sealing in the shoulder area without increasing the thickness of the sealant layer.

[0010] The thickness of the sealant layer is preferably in the range of 2 mm to 5 mm, which ensures puncture sealing properties while preventing uneven distribution of the sealant layer due to flow of the sealant.

[0011] The average thickness S1 [mm] of the region of the sealant layer that overlaps with the side reinforcing layer in the tire width direction is preferably thinner than the average thickness S2 [mm] of the region of the sealant layer that does not overlap with the side reinforcing layer in the tire width direction. By reducing the thickness of the sealant layer near the belt edge, which is easily damaged during high-speed running, it is possible to suppress over-vulcanization and effectively improve high-speed durability.

[0012] The average thickness S1 [mm] of the sealant layer in the region overlapping the side reinforcing layer in the tire width direction and the distance L [mm] from the sealant layer to the carcass layer preferably satisfy the relationship S1 / L ≥ 0.2. By making the average thickness S1 of the sealant layer sufficiently large relative to the distance L, good puncture sealing performance can be ensured.

[0013] The silicone composition is preferably a two-component curing silicone, which has low viscosity immediately after mixing the two components, allowing application even at low temperatures. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a meridian cross-sectional view showing a pneumatic tire according to an embodiment of the present invention. [Figure 2] 2 is an enlarged cross-sectional view showing a shoulder portion of the pneumatic tire of FIG. 1. FIG. [Figure 3] 1 is a cross-sectional view illustrating an example of a method for manufacturing a pneumatic tire according to an embodiment of the present invention. [Figure 4] 4 is a plan view showing a sealant layer formed on the inner surface of the tire in the tread portion of the pneumatic tire of FIG. 3. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0015] The configuration of the present invention will be described in detail below with reference to the accompanying drawings. Figures 1 and 2 show a pneumatic tire according to an embodiment of the present invention. In Figure 1, CL denotes the tire center line.

[0016] As shown in FIG. 1, a pneumatic tire according to an embodiment of the present invention (a run-flat tire in this embodiment) includes a tread portion 1 extending circumferentially of the tire to form an annular shape, a pair of sidewall portions 2 arranged on both sides of the tread portion 1, and a pair of bead portions 3 arranged radially inward of the sidewall portions 2.

[0017] At least one carcass layer 4 (one layer in FIG. 1) made up of a plurality of carcass cords arranged in the radial direction is mounted between a pair of bead portions 3. Organic fiber cords such as nylon and polyester are preferably used as the carcass cords that make up the carcass layer 4. An annular bead core 5 is embedded in each bead portion 3, and a first bead filler 6 made of a rubber composition and having a triangular cross section is disposed on the outer periphery of the bead core 5.

[0018] Meanwhile, multiple belt layers 7 (two layers in FIG. 1) are embedded on the tire outer circumferential side of the carcass layer 4 in the tread portion 1. The belt layers 7 include multiple reinforcing cords that are inclined with respect to the tire circumferential direction, and are arranged so that the reinforcing cords cross each other between the layers. In the belt layers 7, the inclination angle of the reinforcing cords with respect to the tire circumferential direction is set in the range of 10° to 40°, for example. Steel cords are preferably used as the reinforcing cords of the belt layers 7.

[0019] At least one belt cover layer 8 (two layers in FIG. 1 ) is arranged on the outer periphery of the belt layer 7, with the aim of improving high-speed durability. The belt cover layer 8 has at least one reinforcing cord arranged at an angle of, for example, 5° or less relative to the tire circumferential direction. The belt cover layer 8 preferably has a jointless structure in which a strip material made of at least one reinforcing cord aligned and rubber-coated is continuously wound at an angle of substantially 0° relative to the tire circumferential direction. The reinforcing cord of the belt cover layer 8 is preferably an organic fiber cord such as nylon or aramid.

[0020] In the above pneumatic tire, both ends of the carcass layer 4 are folded back around each bead core 5 from the inside to the outside of the tire, and are arranged to encase the bead cores 5 and the first bead fillers 6. A tread rubber layer 10 is arranged on the outer peripheral side of the belt layer 7 and the belt cover layer 8 in the tread portion 1. A side reinforcing layer 11 with a crescent cross section is arranged on the inner side of the carcass layer 4 in the sidewall portion 2 in the tire width direction to enable run-flat running. This side reinforcing layer 11 preferably has a maximum thickness of 5 mm or more. A side rubber layer 12 is arranged on the outer side of the carcass layer 4 in the sidewall portion 2 in the tire width direction. A rim cushion rubber layer 13 is arranged on the outer side of the carcass layer 4 in the bead portion 3 in the tire width direction.

[0021] A second bead filler 14 is arranged along the turned-up portion of the carcass layer 4 on the outer side in the tire width direction of the turned-up portion of the carcass layer 4 in the sidewall portion 2. This second bead filler 14 is arranged so as to overlap in the tire radial direction with the first bead filler 6 and the side reinforcing layer 11. In FIG. 1 , the second bead filler 14 extends in the tire radial direction with one end located midway up the first bead filler 6 and the other end located midway up the side reinforcing layer 11.

[0022] The tire internal structure described above is a typical example of a pneumatic tire, but is not limited thereto. As a component constituting the tire inner surface Ts, an inner liner layer 9 is disposed along the carcass layer 4.

[0023] In the pneumatic tire, a sealant layer 20 is formed continuously in the tire circumferential direction on the tire inner surface Ts of the tread portion 1. The sealant of the sealant layer 20 is composed of a silicone-based composition. The silicone-based composition includes a synthetic polymer compound having a main skeleton formed by siloxane bonds.

[0024] In the above-described pneumatic tire, in which the side reinforcing layer 11 is arranged in the sidewall portion 2, the sealant that constitutes the sealant layer 20 is composed of a silicone-based composition, so the tire does not become hot when applied, as with conventional sealants made of butyl-based rubber, and therefore the tread portion 1 can be prevented from becoming over-vulcanized, and high-speed durability can be improved while the puncture sealing properties of the sealant layer 20 are maintained.

[0025] The above-described pneumatic tire can be manufactured by the following method. First, a pneumatic tire is manufactured as described above, which includes the tread portion 1, the pair of sidewall portions 2, the pair of bead portions 3, and the side reinforcing layer 11. Next, a sealant is applied to the tire inner surface Ts of the tread portion 1 to form the sealant layer 20.

[0026] FIG. 3 shows a specific method for manufacturing a pneumatic tire according to an embodiment of the present invention, and FIG. 4 shows a sealant layer formed on the tire inner surface in the tread portion. In FIG. 3, a sealant extrusion device 31 mixes sealants supplied from pumps 32 and 33 and continuously discharges the mixed sealant as a strip 21 from a nozzle 34. The sealant extrusion device 31 is configured so that the position of the nozzle 34 can be freely changed. Therefore, by moving the nozzle 34 axially while rotating the tire from a state in which the nozzle 34 is close to the tire inner surface Ts, the sealant strip 21 can be arranged spirally on the tire inner surface Ts while being inclined with respect to the tire circumferential direction Tc (see FIG. 4). The spirally arranged sealant strips 21 are in close contact with each other at their circumferential portions. The spirally arranged sealant strips 21 are integrated to form the sealant layer 20.

[0027] The sealant applied to the tire inner surface Ts is composed of a silicone-based composition. This prevents the sealant layer 20 from flowing during high-speed driving, allowing it to maintain the shape it was in when manufactured. Furthermore, since silicone-based compositions have good fluidity even at low temperatures, the temperature of the sealant applied to the tire inner surface Ts is set to 70°C or lower. This reduces the impact of heat on the tire and prevents deterioration of tire performance. If this temperature is 70°C or higher, the impact of heat on the tire will be greater, which will cause deterioration of tire performance. In particular, the temperature of the sealant applied to the tire inner surface Ts is preferably in the range of 5°C to 40°C, more preferably in the range of 10°C to 35°C, and most preferably in the range of 15°C to 30°C.

[0028] As the silicone-based composition constituting the sealant of the sealant layer 20, one-component curing silicone or two-component curing silicone can be used, but it is particularly preferable to use two-component curing silicone. An example of one-component curing silicone is moisture-curing silicone. Two-component curing silicone is composed of a first component and a second component, and mixing these two components initiates a curing reaction, ensuring the stability of the sealant layer 20 after curing. In the above-mentioned device, the first component and the second component of the two-component curing silicone are supplied from pumps 32 and 33, respectively. Two-component curing silicone has low viscosity immediately after mixing the two components, so it can be applied even at low temperatures.

[0029] Two-component curing silicones are composed of, for example, a condensation-curable silyl-terminated polymer, a silane crosslinker, a condensation catalyst, a filler, and the like. Examples of condensation-curable silyl-terminated polymers include polydialkylsiloxanes, alkylphenylsiloxanes, organic polymers having silyl groups (e.g., silyl polyethers, silyl acrylates), and polyisobutylenes having silyl groups. Examples of silane crosslinkers include alkoxy-functional silanes, oximosilanes, acetoxysilanes, and enoxysilanes. Examples of fillers include iron oxide, titanium dioxide, carbon black, and talc. Examples of condensation catalysts include titanates and zirconates. These condensation-curable silyl-terminated polymers, silane crosslinkers, condensation catalysts, and fillers are stored in a first and second liquid form in a combination that does not promote a curing reaction, and are mixed when used.

[0030] In the above pneumatic tire, the radially outer end 11e of the side reinforcing layer 11 is preferably positioned more inward in the tire width direction than the end 7e of the belt layer 7 that is positioned radially innermost among the multiple belt layers 7. Furthermore, the end 20e of the sealant layer 20 is preferably positioned more outward in the tire width direction than the radially outer end 11e of the side reinforcing layer 11. When a foreign object such as a nail penetrates the shoulder portion, where the tire gauge is thin, the amount of air leakage increases significantly. To address this, the thickness of the sealant layer needs to be increased. However, by arranging the ends of the side reinforcing layer 11 and the sealant layer 20 as described above, the amount of air leakage can be reduced by the side reinforcing layer 11, and therefore sufficient puncture sealing performance in the shoulder portion can be ensured without increasing the thickness of the sealant layer 20.

[0031] In particular, the end 11e of the side reinforcing layer 11 is preferably arranged more inward in the tire width direction than the end 7e of the belt layer 7 by a length equivalent to 5% to 20% of the width of the belt layer 7 that is located radially innermost among the multiple belt layers 7, and more preferably arranged more inward in the tire width direction than the end 7e of the belt layer 7 by a length equivalent to 7% to 15%. Furthermore, the width of the sealant layer 20 is preferably 90% or more of the width of the belt layer 7 that has the largest width among the multiple belt layers 7. Furthermore, the end 20e of the sealant layer 20 is preferably arranged more outward in the tire width direction than the end 7e of the belt layer 7 that has the largest width.

[0032] In the pneumatic tire, the thickness of the sealant layer 20 is preferably in the range of 2 mm to 5 mm. This ensures puncture sealing performance while preventing uneven distribution of the sealant layer 20 due to sealant flow. If the thickness of the sealant layer 20 is less than 2 mm, puncture sealing performance will decrease, while if it is greater than 5 mm, uneven distribution of the sealant layer 20 may occur due to sealant flow. The thickness of the sealant layer 20 is the average thickness of the entire sealant layer 20. The thickness of the sealant layer 20 can be calculated from measurements at a total of 40 points, for example, by CT scanning a tire meridian cross section at eight locations around the tire circumference and measuring the thickness of the sealant layer 20 at five points in each image: the tire equator, outer edge positions (on both sides) 10 mm inward in the tire width direction from the edge of the sealant layer 20, and intermediate positions (on both sides) between the tire equator and outer edge positions.

[0033] The average thickness S1 [mm] (see FIG. 2) of the region A1 of the sealant layer 20 that overlaps with the side reinforcing layer 11 in the tire width direction is preferably thinner than the average thickness S2 [mm] (see FIG. 2) of the region A2 of the sealant layer 20 that does not overlap with the side reinforcing layer 11 in the tire width direction. In particular, the ratio S1 / S2 × 100% is preferably set in the range of 50% to 80%. The side reinforcing layer 11 can suppress the amount of air leakage and can assist the puncture sealing performance of the sealant layer 20, so the thickness can be reduced in the region A1 of the sealant layer 20. Reducing the thickness of the sealant layer 20 near the belt edge, which is easily damaged during high-speed driving, contributes to suppressing over-vulcanization, thereby effectively improving high-speed durability. The average thickness S1 is calculated based on the cross-sectional area [mm] of the region A1 of the sealant layer 20 at any tire meridian cross section. 2 ] divided by the length [mm] of the sealant layer 20 measured along the tire inner surface Ts. The average thickness S2 is the thickness obtained by dividing the cross-sectional area [mm 2[mm] by the length [mm] of the sealant layer 20 measured along the tire inner surface Ts. The average thickness S1 and the average thickness S2 are measured in a direction perpendicular to the tire inner surface Ts.

[0034] The average thickness S1 [mm] of the sealant layer 20 in the region A1 and the distance L [mm] (see FIG. 2) from the sealant layer 20 to the carcass layer 4 located at the outermost position in the tire width direction preferably satisfy the relationship S1 / L≧0.2. By making the average thickness S1 of the sealant layer 20 in the region A1 sufficiently large relative to the distance L, good puncture sealing performance can be ensured. If the ratio S1 / L is less than 0.2, the puncture sealing performance deteriorates. Note that the distance L is the shortest distance from the end 20e of the sealant layer 20 in the tire width direction to the outermost layer of the carcass layer 4 located at the outermost position in the tire width direction (if the carcass layer 4 has multiple layers, it includes the thickness of the carcass layer located inside the outermost layer). [Example]

[0035] The tire size was 255 / 40R21 and the tire was equipped with a tread portion, a pair of sidewall portions, and a pair of bead portions, with one carcass layer mounted between the pair of bead portions, with two belt layers arranged on the outer peripheral side of the carcass layer in the tread portion, and a side reinforcing layer with a crescent cross section arranged on the inner side of the carcass layer in the sidewall portion in the tire width direction. In this pneumatic tire, a sealant layer was formed on the inner surface of the tire in the tread portion, and tires of conventional example and examples 1 to 9 were manufactured with the type of sealant, the end positions of the side reinforcing layer, the end positions of the sealant layer, the thickness of the sealant layer, the relationship between the average thickness S1 and the average thickness S2, the ratio S1 / L, the sealant application temperature, and the type of silicone-based composition set as shown in Table 1.

[0036] In Table 1, "inner" in "end position of side reinforcing layer" means that the end of the side reinforcing layer is located more inward in the tire width direction than the end of the belt layer that is located most inward in the tire radial direction among the multiple belt layers. In Table 1, "inner" in "end position of sealant layer" means that the end of the sealant layer is located more inward in the tire width direction than the end of the side reinforcing layer, and "outer" in "end position of sealant layer" means that the end of the sealant layer is located more outward in the tire width direction than the end of the side reinforcing layer.

[0037] These test tires were evaluated for high-speed durability and puncture sealing performance by the following test methods, and the results are shown in Table 1.

[0038] Fast durability: Each test tire was mounted on a wheel with a rim size of 21 x 9.0J and attached to an indoor drum testing machine, with the air pressure set to 360 kPa and a load set to 80% of the maximum load capacity. The tire was driven under the conditions specified in UN R30 up to a speed corresponding to the speed symbol indicated on the tire, and thereafter the speed was increased by 10 km / h every 10 minutes, and the speed reached until the tire broke was measured. The evaluation results were expressed as an index, with the conventional example being set at 100. The higher the index value, the better the high-speed durability.

[0039] Puncture sealing: Each test tire was mounted on a wheel with a rim size of 21 x 9.0J, and the initial air pressure was set to 250 kPa. The temperature was set to 23°C (room temperature). A nail with a diameter of 4.0 mm was driven into the shoulder, and the nail was then removed. The tire was left for one hour, and the air pressure was then measured again. The evaluation results were expressed as an index, with the conventional example being set at 100. The higher the index value, the better the puncture sealing ability.

[0040] [Table 1]

[0041] As can be seen from Table 1, the pneumatic tires of Examples 1 to 9 were able to improve high-speed durability while ensuring puncture sealing performance compared to the conventional tire.

[0042] The present disclosure includes the following inventions [1] to [7]. Invention [1] is a pneumatic tire comprising a tread portion extending circumferentially in a ring shape, a pair of sidewall portions arranged on both sides of the tread portion, and a pair of bead portions arranged radially inward of the sidewall portions, with at least one carcass layer mounted between the pair of bead portions, with multiple belt layers arranged on the outer periphery of the carcass layer in the tread portion, and a side reinforcing layer with a crescent cross section arranged on the inner side of the carcass layer in the sidewall portions in the tire width direction, wherein a sealant layer is formed on the inner surface of the tire in the tread portion, and the sealant in the sealant layer is composed of a silicone-based composition. Invention [2] is a pneumatic tire according to invention [1], characterized in that the end of the side reinforcing layer is positioned more inward in the tire width direction than the end of the belt layer, and the end of the sealant layer is positioned more outward in the tire width direction than the end of the side reinforcing layer. Invention [3] is the pneumatic tire according to invention [1] or [2], characterized in that the thickness of the sealant layer is in the range of 2 mm to 5 mm. Invention [4] is a pneumatic tire according to any one of inventions [1] to [3], characterized in that the average thickness S1 [mm] of the area of ​​the sealant layer that overlaps with the side reinforcing layer in the tire width direction is thinner than the average thickness S2 [mm] of the area of ​​the sealant layer that does not overlap with the side reinforcing layer in the tire width direction. Invention [5] is a pneumatic tire according to any one of inventions [1] to [4], characterized in that the average thickness S1 [mm] of the region of the sealant layer that overlaps with the side reinforcing layer in the tire width direction and the distance L [mm] from the sealant layer to the carcass layer satisfy the relationship S1 / L≧0.2. Invention [6] is the pneumatic tire according to any one of inventions [1] to [5], characterized in that the silicone composition is a two-component curing silicone. Invention [7] is a method for manufacturing a pneumatic tire according to any one of Inventions [1] to [6], characterized in that after manufacturing a pneumatic tire excluding the sealant layer, when applying a sealant to the inner surface of the tire in the tread portion to form the sealant layer, the temperature of the sealant applied to the inner surface of the tire is set to 70°C or less. [Explanation of symbols]

[0043] 1 Tread section 2 Sidewall 3 Bead section 4 carcass layers 5 bead core 6 Bead filler 7 Belt Layer 11 Side reinforcement layer 20 Sealant Layer CL Tire centerline Ts tire inner surface

Claims

1. A pneumatic tire comprising a tread portion extending in the tire circumferential direction and forming an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed radially inward of the sidewall portions, at least one carcass layer being fitted between the pair of bead portions, a plurality of belt layers being disposed on the outer peripheral side of the carcass layer in the tread portion, and a side reinforcing layer having a crescent cross section being disposed on the inner side of the carcass layer in the sidewall portions in the tire width direction, A pneumatic tire characterized in that a sealant layer is formed on the inner surface of the tire in the tread portion, and the sealant in the sealant layer is composed of a silicone-based composition.

2. 2. The pneumatic tire according to claim 1, wherein an end of the side reinforcing layer is disposed inward in the tire width direction from an end of the belt layer, and an end of the sealant layer is disposed outward in the tire width direction from an end of the side reinforcing layer.

3. 3. The pneumatic tire according to claim 1, wherein the sealant layer has a thickness in the range of 2 mm to 5 mm.

4. 3. The pneumatic tire according to claim 1, wherein an average thickness S1 [mm] of a region of the sealant layer that overlaps with the side reinforcing layer in the tire width direction is thinner than an average thickness S2 [mm] of a region of the sealant layer that does not overlap with the side reinforcing layer in the tire width direction.

5. 3. The pneumatic tire according to claim 1, wherein an average thickness S1 [mm] of a region of the sealant layer that overlaps with the side reinforcing layer in the tire width direction and a distance L [mm] from the sealant layer to the carcass layer satisfy the relationship S1 / L≧0.

2.

6. 3. The pneumatic tire according to claim 1, wherein the silicone-based composition is a two-component curing silicone.

7. A method for manufacturing the pneumatic tire according to claim 1 or 2, After manufacturing a pneumatic tire excluding the sealant layer, a temperature of the sealant applied to the tire inner surface being set to 70°C or lower when forming the sealant layer by applying the sealant to the tire inner surface in the tread portion.

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