Pneumatic tire and manufacturing method for the same

Abstract

To provide a pneumatic tire that enables a sealant layer to exert sound absorption effect, 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 a sealant layer 20 having a structure in which band materials 21 of sealant extending in a tire circumferential direction are arranged in parallel is formed on an inner surface 10 of the tire, where thicknesses of the band materials 21 of sealant are ununiform in a width direction of the band materials 21 and the sealant is composed of silicone-based compositions.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a pneumatic tire having a sealant layer on its inner surface and a manufacturing method thereof, and more particularly to a pneumatic tire that enables the sealant layer to exhibit a sound absorbing effect and a manufacturing method thereof. [Background technology]

[0002] It has been proposed to provide a sealant layer in a pneumatic tire radially inward of an inner liner layer in the tread portion of the tire. In such a pneumatic tire, when a foreign object such as a nail penetrates the tread portion, the sealant flows into the through-hole, thereby suppressing a decrease in air pressure and enabling the tire to continue running.

[0003] Conventionally, sealants constituting a sealant layer have generally been rubber compositions mainly composed of butyl rubber (see, for example, Patent Documents 1 to 3). Examples of butyl rubber include butyl rubber (IIR) and halogenated butyl rubbers such as brominated butyl rubber (Br-IIR) and chlorinated butyl rubber (Cl-IIR). Such sealants are applied to the inner surface of a tire in a softened state by heating to a high temperature (see, for example, Patent Document 4). More specifically, a strip of sealant that has been softened by heating to a high temperature is spirally arranged on the inner surface of the tire in the circumferential direction of the tire to form a sealant layer.

[0004] On the other hand, in pneumatic tires, noise is generated due to the tread pattern and structure, and in recent years, there has been a demand for reducing such noise. Therefore, if it is possible to impart a sound-absorbing function to the sealant layer, restrictions on the tread pattern and structure can be reduced, and the degree of freedom in designing pneumatic tires can be increased. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6583456 [Patent Document 2] Patent No. 6620851 [Patent Document 3] Patent No. 7319533 [Patent Document 4] Patent No. 6124967 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a pneumatic tire that is capable of exhibiting a sound absorbing effect due to a sealant layer, and a method for manufacturing the same. [Means for solving the problem]

[0007] In order to achieve the above object, a pneumatic tire of the present invention includes a tread portion extending in a circumferential direction of the tire to form an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on the radially inner side of the sidewall portions, The tire has a sealant layer formed on the inner surface of the tire, which has a structure in which strips of sealant extending in the tire circumferential direction are arranged in parallel, the thickness of the sealant strips is non-uniform in the width direction of the strips, and the sealant is composed of a silicone-based composition.

[0008] In order to achieve the above object, a method for manufacturing a pneumatic tire according to the present invention is a method for manufacturing the above-mentioned pneumatic tire, comprising: After manufacturing a pneumatic tire excluding the sealant layer, When a sealant made of a silicone-based composition is applied to the inner surface of the tire to form the sealant layer, the temperature of the sealant applied to the inner surface of the tire is set to be lower than 70°C. [Effects of the Invention]

[0009] As a result of extensive research into the sound-absorbing effect of a sealant layer, the inventors discovered that by forming irregularities on the surface of the sealant layer, like the wall surface of an anechoic chamber, the sealant layer can effectively absorb noise generated by a pneumatic tire, leading to the present invention.

[0010] Specifically, in the present invention, a sealant layer having a structure in which strips of sealant extending in the tire circumferential direction are arranged in parallel is formed on the inner surface of the tire, and the thickness of the sealant strip is non-uniform in the width direction of the strip, thereby forming irregularities on the surface of the sealant layer, thereby absorbing noise generated by the pneumatic tire. Furthermore, since the sealant is composed of a silicone-based composition, the shape stability of the sealant layer is improved, allowing the sound-absorbing effect of the sealant layer to be maintained for a long period of time. Furthermore, a sealant composed of a silicone-based composition can be applied at low temperatures; for example, the temperature of the sealant applied to the inner surface of the tire can be lowered to below 70°C, which has the advantage of reducing the thermal effects on the tire and preventing deterioration of tire performance.

[0011] In the present invention, it is preferable that the sealant layer is disposed at least in the tread portion. By disposing the sealant layer at least in the tread portion, sufficient sealing properties can be exhibited when a foreign object such as a nail penetrates the tread portion. Moreover, since the sealant layer can easily absorb vibrations from the road surface, this is also preferable from the viewpoint of noise reduction.

[0012] In the present invention, it is preferable that the sealant strip is arranged spirally along the tire circumferential direction and the strip is inclined in the same direction relative to the tire circumferential direction. When the sealant strip is arranged spirally along the tire circumferential direction, the strip can be continuously applied to the tire inner surface, which allows for efficient formation of the sealant layer and increases productivity of pneumatic tires.

[0013] In the present invention, the thickness of the sealant strip is preferably greater at one end of the strip than at the other end in the width direction of the strip. In particular, the ratio of the thickness T1 of the sealant strip at one end to the thickness T2 of the sealant strip at the other end preferably satisfies the relationship 0.5≦T1 / T2≦0.9. By having the sealant strip have a shape that approximates a trapezoid, it is possible to effectively absorb noise generated in a pneumatic tire.

[0014] In the present invention, the silicone composition is preferably a two-component curing silicone, which has low viscosity immediately after mixing the two components, making it possible to apply the composition even at low temperatures.

[0015] In the present invention, the average thickness of the sealant layer is preferably in the range of 2.0 mm to 5.0 mm, which makes it possible to ensure sealing properties while suppressing uneven distribution of the sealant layer due to flow of the sealant.

[0016] In the present invention, the glass transition temperature of the sealant is preferably in the range of −120° C. to −40° C. By using a sealant with a low glass transition temperature, good sealing properties can be ensured in low-temperature environments.

[0017] In the present invention, when a belt layer including belt cords inclined with respect to the tire circumferential direction is embedded in the tread portion, the width of the sealant layer is preferably 90% or more of the width of the belt layer located at the innermost position in the tire radial direction. In particular, it is preferable that the end of the sealant layer is located outward in the tire width direction than the end of the belt layer located at the innermost position in the tire radial direction. By making the width of the sealant layer sufficiently large, sufficient sealing performance can be ensured.

[0018] In the present invention, when a belt cover layer including organic fiber cords oriented in the tire circumferential direction on the outer peripheral side of the belt layer is embedded in the tread portion, it is preferable that the end of the sealant layer is disposed on the outer side in the tire width direction than the end of the belt cover layer. By making the width of the sealant layer sufficiently large, sufficient sealing performance can be ensured.

[0019] In the present invention, it is preferable that the distance L from the belt layer located at the innermost position in the tire radial direction to the sealant layer is 10 mm or less at all locations of the belt layer, which makes it easier for the sealant to flow into the belt layer when a foreign object such as a nail penetrates the tread portion, thereby ensuring good sealing properties. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a meridian cross-sectional view showing a pneumatic tire according to an embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing a main part of the pneumatic tire of FIG. [Figure 3] 2 is a plan view showing a belt layer, a belt cover layer, and a sealant layer of the pneumatic tire of FIG. 1. FIG. [Figure 4] 1A to 1C show various cross-sectional shapes of a sealant strip, with (a) to (c) being transverse cross-sectional views. [Figure 5] 2 is a cross-sectional view illustrating a method for manufacturing the pneumatic tire of FIG. 1. [Figure 6] 2 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. 1. FIG. [Figure 7] FIG. 2 is a meridian cross-sectional view showing a pneumatic tire according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the accompanying drawings, in which: Figures 1 to 3 show a pneumatic tire according to an embodiment of the present invention.

[0022] As shown in FIG. 1, the pneumatic tire of this embodiment includes a tread portion 1 extending circumferentially in a ring shape, a pair of sidewall portions 2, 2 arranged on both sides of the tread portion 1, and a pair of bead portions 3, 3 arranged radially inward of the sidewall portions 2.

[0023] A carcass layer 4 is mounted between a pair of bead portions 3, 3. This carcass layer 4 includes a plurality of carcass cords extending in the tire radial direction, and is folded back from the inside to the outside of the tire around a bead core 5 disposed in each bead portion 3. A 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.

[0024] On the other hand, multiple belt layers 7 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. These belt layers 7 include multiple belt cords that are inclined with respect to the tire circumferential direction, and are arranged so that the belt cords cross each other between the layers. In the belt layers 7, the inclination angle of the belt 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 belt cords of the belt layers 7.

[0025] At least one belt cover layer 8 is arranged on the outer periphery of the belt layer 7, with the aim of improving high-speed durability, and is made up of reinforcing cords arranged at an angle of, for example, 5° or less relative to the tire circumferential direction. This belt cover layer 8 preferably has a jointless structure in which a strip material made of at least one reinforcing cord that has been 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 polyethylene terephthalate (PET).

[0026] The tire internal structure described above is a typical example of a pneumatic tire, but is not limited to this. Various grooves, including a plurality of main grooves 11 extending in the tire circumferential direction, are formed in the tread portion 1.

[0027] In the pneumatic tire described above, a sealant layer 20 is formed continuously in the tire circumferential direction on the tire inner surface 10 in the tread portion 1. The center position of the sealant layer 20 in the tire width direction preferably coincides with the tire equator, but the center position may be offset from the tire equator to either side in the tire width direction. The distance in the tire width direction between the center position of the sealant layer 20 in the tire width direction and the tire equator is preferably 10 mm or less, more preferably 5 mm or less. This prevents the sealant layer 20 from adversely affecting tire balance. As shown in FIG. 3 , the sealant layer 20 has a structure in which sealant strips 21 extending in the tire circumferential direction Tc are arranged in parallel. More specifically, the sealant layer 20 has a structure in which the sealant strips 21 are arranged spirally along the tire circumferential direction. 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.

[0028] 4(a) to 4(c) show various cross-sectional shapes of the sealant strip. As shown in FIGS. 4(a) to 4(c), the thickness of the sealant strip 21 is non-uniform across the width of the strip 21. More specifically, the thickness of the sealant strip 21 gradually increases from one end of the strip 21 across the width of the strip 21 toward the other, forming a step at the boundary between adjacent circumferential portions of the strip 21 across the tire. In FIG. 4(a), the top surface of the strip 21 (the surface opposite to the surface that contacts the tire inner surface 10) is flat. In FIG. 4(b), the top surface of the strip 21 is a concave curved surface. In FIG. 4(c), the top surface of the strip 21 is a bulged curved surface.

[0029] In the pneumatic tire described above, a sealant layer 20 having a structure in which sealant strips 21 extending in the tire circumferential direction are arranged in parallel is formed on the tire inner surface 10, and the thickness of the sealant strips 21 is uneven across the width of the strips 21, forming irregularities on the surface of the sealant layer 20, thereby absorbing noise generated by the pneumatic tire. Furthermore, since the sealant is composed of a silicone-based composition, the shape stability of the sealant layer 20 is improved, allowing the sound-absorbing effect of the sealant layer 20 to be maintained for a long period of time. Furthermore, a sealant composed of a silicone-based composition can be applied at low temperatures; for example, the temperature of the sealant applied to the tire inner surface can be lowered to below 70°C, which has the advantage of reducing the thermal effects on the tire and preventing deterioration of tire performance.

[0030] In the above pneumatic tire, the sealant layer 20 is disposed at least in the tread portion 1, and in this case, sufficient sealing performance can be exhibited when a foreign object such as a nail penetrates the tread portion 1. Moreover, the sealant layer 20 easily absorbs vibrations from the road surface, which is also preferable from the viewpoint of noise reduction. However, the sealant layer 20 can be disposed in the sidewall portion 2 in addition to the tread portion 1, or it can be disposed only in the sidewall portion 2.

[0031] In the pneumatic tire described above, it is preferable that the sealant strip 21 is arranged spirally along the tire circumferential direction and that the strip 21 is inclined in the same direction relative to the tire circumferential direction. When the sealant strip 21 is arranged spirally along the tire circumferential direction, the strip 21 can be continuously applied to the tire inner surface 10, which allows the sealant layer 20 to be formed efficiently and increases the productivity of pneumatic tires.

[0032] In the pneumatic tire, the thickness of the sealant strip 21 is preferably greater at one end of the sealant strip 21 than at the other end of the sealant strip 21 in the width direction. In particular, as shown in FIGS. 4(a) to 4(c), the ratio of the thickness T1 of the sealant strip 21 at one end of the width direction to the thickness T2 of the sealant strip 21 at the other end of the width direction preferably satisfies the relationship 0.5≦T1 / T2≦0.9. The trapezoidal shape of the sealant strip 21 effectively absorbs noise generated in the pneumatic tire. If the value of T1 / T2 is less than 0.5, extrusion of the strip 21 becomes difficult, reducing the productivity of the pneumatic tire. Conversely, if the value is greater than 0.9, the unevenness formed on the surface of the sealant layer 20 becomes small, reducing the noise reduction effect. In particular, the ratio of the thickness T1 of the sealant strip 21 at one end of the width direction to the thickness T2 of the sealant strip 21 at the other end of the width direction preferably satisfies the relationship 0.6≦T1 / T2≦0.8. The thickness T1 of the sealant at one end of the width of the strip 21 and the thickness T2 at the other end are thicknesses measured at positions 10% of the width W of the strip 21 from each end face of the strip 21 in the width direction.

[0033] 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, a pair of sidewall portions 2, and a pair of bead portions 3, and in which the belt layer 7 and belt cover layer 8 are embedded in the tread portion 1. Next, a sealant made of a silicone-based composition is applied to the tire inner surface 10 in the tread portion 1 to form the sealant layer 20.

[0034] FIG. 5 shows a specific manufacturing method for the pneumatic tire of FIG. 1, and FIG. 6 shows a sealant layer formed on the tire inner surface in the tread portion. In FIG. 5, 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 10, the sealant strip 21 can be arranged spirally on the tire inner surface 10 while being inclined with respect to the tire circumferential direction Tc (see the figure). 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. Furthermore, when the sealant strip 21 is continuously extruded from the nozzle 34 of the sealant extrusion device 31, the cross-sectional shape of the strip 21 can be determined based on the shape of the opening of the nozzle 34.

[0035] In the pneumatic tire described above, a sealant layer 20 is formed on the tire inner surface 10 of the tread portion 1, with a sealant strip 21 spirally arranged along the tire circumferential direction. Because the sealant is composed of a silicone-based composition, the circumferential portions of the sealant strip 21 fit together easily during the curing reaction of the silicone-based composition, improving the integrity of the circumferential portions of the sealant strip 21, thereby improving the sealing performance of the sealant layer 20. Furthermore, because the circumferential portions of the sealant strip 21 are well-integrated, the sealant layer 20 is less likely to flow toward the center of the tire width direction due to centrifugal force generated during tire rotation, which also contributes to improved sealing performance. Furthermore, using a silicone-based composition as the sealant for the sealant layer 20 has the advantages of excellent weather resistance and low temperature dependency of physical properties.

[0036] When a sealant made of a rubber composition mainly containing butyl rubber is used, a sealant layer is formed by heating a strip of sealant to a high temperature and softening it, and then spirally arranging it around the tire's inner surface in the circumferential direction. However, in a sealant layer formed in this manner, the sealant cools before the wrapped portions of the sealant strip have time to blend together, resulting in poor unity between the wrapped portions of the sealant strip and resulting in insufficient sealing by the sealant layer.

[0037] Because silicone-based compositions have good fluidity even at low temperatures, it is preferable to set the temperature of the sealant applied to the tire inner surface 10 to below 70°C. This reduces the thermal impact on the tire and prevents deterioration of tire performance. If this temperature is 70°C or higher, the thermal impact on the tire will be greater, which will cause deterioration of tire performance. In particular, it is desirable for the temperature of the sealant applied to the tire inner surface 10 to be 35°C or lower. Furthermore, from the viewpoint of the fluidity of the silicone-based composition, it is preferable for the lower limit of the temperature of the sealant applied to the tire inner surface 10 to be 20°C.

[0038] The silicone-based composition constituting the sealant of the sealant layer 20 can be a one-component curing silicone or a two-component curing silicone, with two-component curing silicone being particularly preferred. Examples of one-component curing silicones include moisture-curing silicone. Two-component curing silicones are composed of a first component and a second component, and mixing these components initiates a curing reaction, ensuring the stability of the sealant layer 20 after curing. In the above-described 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 silicones have low viscosity immediately after mixing, allowing them to be applied even at low temperatures. In particular, two-component curing silicones that take 5 days or more to fully cure are preferred.

[0039] 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.

[0040] In the above pneumatic tire, the glass transition temperature of the sealant of the sealant layer 20 is preferably in the range of -120°C to -40°C. By using a sealant with a low glass transition temperature, good puncture sealing performance in low-temperature environments can be ensured. If the glass transition temperature of the sealant is higher than -40°C, puncture sealing performance in low-temperature environments will be reduced.

[0041] In the above-described pneumatic tire, the average thickness S of the sealant layer 20 is preferably in the range of 2.0 mm to 5.0 mm, as shown in Fig. 2. This ensures puncture sealing performance while preventing uneven distribution of the sealant layer 20 due to sealant flow. If the average thickness S of the sealant layer 20 is less than 2.0 mm, puncture sealing performance will be reduced, while if it is greater than 5.0 mm, uneven distribution of the sealant layer 20 may occur due to sealant flow. The average thickness S of the sealant layer 20 can be calculated from the measurements at the eight locations, for example, by CT scanning a tire meridian cross section at eight locations around the tire circumference, measuring the average thickness (cross-sectional area of ​​the sealant layer 20 / width of the sealant layer 20 measured along the tire inner surface 10) in each of the images.

[0042] In the above pneumatic tire, when a belt layer 7 (7A, 7B) including belt cords inclined with respect to the tire circumferential direction is embedded in the tread portion 1 as shown in FIGS. 1 and 2, The width Ws of the sealant layer 20 is preferably 90% or more of the width Wb of the belt layer 7A located at the innermost position in the tire radial direction. In particular, it is preferable that the end of the sealant layer 20 is located outward in the tire width direction than the end of the belt layer 7A located at the innermost position in the tire radial direction. By making the width Ws of the sealant layer 20 sufficiently larger than the width Wb of the belt layer 7A, punctures in the pneumatic tire can be effectively prevented. Here, if the width Ws of the sealant layer 20 is less than 90% of the width Wb of the belt layer 7A, puncture sealing performance will be reduced.

[0043] For the same reason, when a belt cover layer 8 containing organic fiber cords oriented in the tire circumferential direction on the outer peripheral side of the belt layer 7 is embedded in the tread portion 1, it is preferable that the ends of the sealant layer 20 are positioned further outward in the tire width direction than the ends of the belt cover layer 8. By making the width of the sealant layer 20 sufficiently large, punctures of the pneumatic tire can be effectively prevented.

[0044] In the above pneumatic tire, as shown in Fig. 2, it is preferable that the distance (shortest distance) L from the belt layer 7A located at the innermost position in the tire radial direction to the sealant layer 20 is 10 mm or less at all points of the belt layer 7A. This makes it easier for the sealant to flow into the belt layer 7A when a foreign object such as a nail penetrates the tread portion 1, thereby ensuring good puncture sealing performance. If there is a portion where the distance L from the belt layer 7A to the sealant layer 20 is greater than 10 mm, there is a risk that the puncture sealing performance in that portion will be insufficient.

[0045] In the pneumatic tire, it is preferable that the ratio of the thickness S of the sealant layer 20 to the distance L from the belt layer 7A located at the innermost side in the tire direction to the sealant layer 20 satisfies the relationship S / L≧0.3. By making the thickness S of the sealant layer 20 sufficiently large relative to the distance L, good puncture sealing performance can be ensured. If the ratio S / L is less than 0.3, the puncture sealing performance deteriorates.

[0046] FIG. 7 shows a pneumatic tire according to another embodiment of the present invention. In FIG. 7, a sound-absorbing material 40 is disposed along the tire circumferential direction on the tire radially inward side of the sealant layer 20. The sound-absorbing material 40 is made of a porous material with open cells and has predetermined sound-absorbing properties based on its porous structure. Polyurethane foam is preferably used as the porous material for the sound-absorbing material 40. After the sealant layer 20 is formed, the sound-absorbing material 40 is attached to the sealant layer 20 using the adhesiveness of the sealant layer 20. In this case, the sound-absorbing material 40 is disposed on the sealant layer 20, which is applied at a low temperature, so damage to the sound-absorbing material 40 is avoided and its sound-absorbing effect can be maintained. The sound-absorbing material 40 is disposed intermittently along the tire circumferential direction. This allows the sound-absorbing effect of the sealant layer 20 to be exerted in areas where the sound-absorbing material 40 is not present. [Example]

[0047] In a pneumatic tire having a tire size of 205 / 55R16 and equipped with a tread portion, a pair of sidewall portions, and a pair of bead portions, a sealant layer having a structure in which a strip of sealant is spirally arranged along the tire circumferential direction is formed on the inner surface of the tire in the tread portion, and tires of the conventional example, comparative example 1, and examples 1 to 9 were produced with various variations as shown in Table 1 in terms of the constituent material of the sealant layer, the thickness ratio T1 / T2 of the thickness T1 at one end of the sealant strip in the width direction to the thickness T2 at the other end, the average thickness S of the sealant layer, the ratio of the width of the sealant layer to the width of the belt layer, the difference in the width of the sealant layer to the width of the belt cover layer, and the distance L from the belt layer located at the innermost position in the tire radial direction to the sealant layer.

[0048] These test tires were evaluated for quietness, sealing ability, and productivity by the following test methods, and the results are shown in Table 1.

[0049] Quiet: Each test tire was mounted on a 16x6.5J rim wheel, air-pressurized to 250kPa, and fitted to a test vehicle (small electric vehicle), and the acceleration passing noise (dB) was measured when the tire was driven on a paved road. The evaluation results were expressed as an index using the reciprocal of the measured value, with the conventional example being set at 100. The higher the index value, the better the quietness.

[0050] Sealability: Each test tire was mounted on a 16x6.5J rim wheel and initially inflated to 250kPa. A 4.0mm nail was driven into the tread, the nail was removed, and the tire was left for one hour before the air pressure was measured again to determine the rate of pressure drop relative to the initial air pressure. The evaluation results were indicated by a "◎" if the rate of pressure drop was 2% or less, a "○" if the rate was more than 2% but less than 7%, a "△" if the rate was more than 7% but less than 20%, and an "×" if the rate of pressure drop was more than 20%.

[0051] Productivity: For each test tire, the time required to apply the sealant strip to the tire's inner surface and form a sealant layer was measured. The evaluation results were expressed as an index using the reciprocal of the measurement value, with the conventional example being set at 100. A higher index value indicates higher productivity.

[0052] [Table 1]

[0053] As can be seen from Table 1, the tires of Examples 1 to 9 all had good noise reduction properties compared to Conventional Example 1 and Comparative Example 1, and the effect of reducing noise generated from the tire based on the structure of the sealant layer was confirmed.

[0054] The present disclosure includes the following inventions [1] to

[12] . Invention [1] is a pneumatic tire having 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 on the tire radially inner side of the sidewall portions, The pneumatic tire is characterized in that a sealant layer having a structure in which strips of sealant extending in the tire circumferential direction are arranged in parallel is formed on the inner surface of the tire, the thickness of the sealant strips is non-uniform in the width direction of the strips, and the sealant is composed of a silicone-based composition. Invention [2] is the pneumatic tire according to invention [1], characterized in that the sealant layer is disposed at least in the tread portion. Invention [3] is a pneumatic tire according to invention [1] or [2], characterized in that the sealant strip is arranged spirally along the tire circumferential direction, and the strip is inclined in the same direction relative to the tire circumferential direction. Invention [4] is a pneumatic tire according to any one of inventions [1] to [3], characterized in that the thickness of the sealant strip is greater at one end side of the strip in the width direction than at the other end side of the strip. Invention [5] is a pneumatic tire according to any one of inventions [1] to [4], characterized in that the ratio of the thickness T1 of the sealant strip at one end to the thickness T2 at the other end satisfies the relationship 0.5≦T1 / T2≦0.9. 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 the pneumatic tire according to any one of inventions [1] to [6], characterized in that the average thickness of the sealant layer is in the range of 2.0 mm to 5.0 mm. Invention [8] is the pneumatic tire according to any one of inventions [1] to [7], characterized in that the glass transition temperature of the sealant is in the range of -120°C to -40°C. Invention [9] is a pneumatic tire according to any one of inventions [1] to [8], characterized in that a belt layer including belt cords inclined relative to the tire circumferential direction is embedded in the tread portion, and the width of the sealant layer is 90% or more of the width of the belt layer located at the innermost position in the tire radial direction. Invention

[10] is a pneumatic tire according to invention [9], characterized in that a belt cover layer including organic fiber cords oriented in the tire circumferential direction on the outer peripheral side of the belt layer is embedded in the tread portion, and an end of the sealant layer is positioned outward in the tire width direction from an end of the belt cover layer. Invention

[11] is the pneumatic tire according to invention [9] or

[10] , characterized in that the distance L from the belt layer located at the innermost position in the tire radial direction to the sealant layer is 10 mm or less at all points of the belt layer. Invention

[12] is a method for manufacturing a pneumatic tire according to any one of Inventions [1] to

[11] , After manufacturing a pneumatic tire excluding the sealant layer, This is a method for manufacturing a pneumatic tire, characterized in that when a sealant made of a silicone-based composition is applied to the inner surface of the tire to form the sealant layer, the temperature of the sealant applied to the inner surface of the tire is lowered to below 70°C. [Explanation of symbols]

[0055] 1 Tread section 2 Sidewall 3 Bead section 4 carcass layers 5 bead core 6 Bead filler 7 Belt Layer 8 Belt cover layer 10 Tire inner surface 20 Sealant Layer 21 Sealant Strip 40 Sound-absorbing material

Claims

1. A pneumatic tire having a tread portion extending in a tire circumferential direction to form an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on the tire radially inner side of the sidewall portions, A pneumatic tire comprising: a sealant layer formed on the inner surface of the tire; the sealant layer having a structure in which strips of sealant extending in the tire circumferential direction are arranged in parallel; the thickness of the sealant strips is non-uniform in the width direction of the strips; and the sealant is composed of a silicone-based composition.

2. 2. The pneumatic tire according to claim 1, wherein the sealant layer is disposed at least in the tread portion.

3. 3. The pneumatic tire according to claim 1, wherein the sealant strip is arranged spirally along the tire circumferential direction, and the strip is inclined in the same direction relative to the tire circumferential direction.

4. 3. The pneumatic tire according to claim 1, wherein the thickness of the sealant strip is greater at one end of the strip than at the other end in the width direction of the strip.

5. 5. The pneumatic tire according to claim 4, wherein a ratio of a thickness T1 at the one end of the sealant strip to a thickness T2 at the other end satisfies the relationship 0.5≦T1 / T2≦0.

9.

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

7. 3. The pneumatic tire according to claim 1, wherein the sealant layer has an average thickness in the range of 2.0 mm to 5.0 mm.

8. 3. The pneumatic tire according to claim 1, wherein the sealant has a glass transition temperature in the range of -120°C to -40°C.

9. 3. The pneumatic tire according to claim 1, wherein a belt layer including belt cords inclined relative to the tire circumferential direction is embedded in the tread portion, and the width of the sealant layer is 90% or more of the width of the belt layer located at the innermost side in the tire radial direction.

10. 10. The pneumatic tire according to claim 9, wherein a belt cover layer including organic fiber cords oriented in the tire circumferential direction on an outer peripheral side of the belt layer is embedded in the tread portion, and an end of the sealant layer is disposed outward in the tire width direction from an end of the belt cover layer.

11. The pneumatic tire according to claim 9, wherein the distance L from the belt layer located at the innermost position in the tire radial direction to the sealant layer is 10 mm or less at all points of the belt layer.

12. A method for manufacturing the pneumatic tire according to claim 1 or 2, After manufacturing a pneumatic tire excluding the sealant layer, a sealant layer formed on the inner surface of the tire by applying a sealant made of a silicone-based composition to the inner surface of the tire, the sealant having a temperature lower than 70°C.

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