Pneumatic tire

Abstract

To provide a pneumatic tire that makes it possible to ensure good sealing performance and to improve noise reduction performance.SOLUTION: A pneumatic tire includes a tread portion 1, a pair of sidewall portions 2, and a pair of bead portions 3. A sealant layer 20 is formed on a tire inner surface 10 of the tread portion 1, where a sealant of the sealant layer 20 comprises a silicone-based composition, and the sealant layer 20 has a porous structure.SELECTED DRAWING: Figure 2

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 more particularly to a pneumatic tire that ensures good sealing properties and improves quietness. [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 containing 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).

[0004] Meanwhile, with the shift to electric vehicles, there is a demand for reducing noise generated by pneumatic tires. One method for reducing this noise is to install a sound-absorbing sponge made of urethane foam on the inner surface of the tire in the tread area. However, installing a sound-absorbing sponge on the inner surface of the tire makes it impossible to install an effective sealant layer in that area. Therefore, it is difficult to achieve both the sound-absorbing effect of the sound-absorbing sponge and the puncture sealing effect of the sealant layer. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6583456 [Patent Document 2] Patent No. 6620851 [Patent Document 3] Patent No. 7319533 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 ensures good sealing properties and also makes it possible to improve quietness. [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 is characterized in that a sealant layer is formed on the inner surface of the tread portion, the sealant of the sealant layer being composed of a silicone-based composition, and the sealant layer has a porous structure. [Effects of the Invention]

[0008] In the present invention, a sealant layer is formed on the inner surface of the tire in the tread portion, and since the sealant layer has a porous structure, the sealant layer not only exhibits good sealing properties but also contributes to improved noise reduction due to its porous structure. In particular, since a sealant made from a silicone composition has better shape stability when cured than a sealant made from a butyl rubber, it can maintain its porous structure even during driving, effectively improving noise reduction.

[0009] In the present invention, the porous structure of the sealant layer preferably contains closed cells and open cells, and the open cell percentage Co, calculated from the total closed cell volume Vc and the total open cell volume Vo as Co = Vo / (Vc + Vo) × 100%, is preferably in the range of 30% to 80%. By having the open cell percentage Co in this range, it is possible to achieve a good balance between sealing performance and noise reduction.

[0010] In the present invention, the density δ of the sealant layer is 20 kg / m 3 ~200kg / m 3 It is preferable that the density δ of the sealant layer is in the above range. By having the density δ of the sealant layer in the above range, it is possible to improve the balance between sealing performance and noise reduction. The density δ of the sealant layer is the apparent density measured in accordance with JIS-K7222.

[0011] In the present invention, the number of cell bubbles n contained in the sealant layer is preferably in the range of 20 cells / 25 mm to 100 cells / 25 mm. Having the number of cell bubbles n contained in the sealant layer in the above range allows for improved noise reduction without increasing manufacturing costs. The number of cell bubbles n is the number of cells measured in accordance with JIS-K6767. That is, using a 25 mm-long fabric counting glass with graduations every 1 mm, the number of cell bubbles per 25 mm in each direction (width / height / depth) of a test piece of the sealant layer is counted, and the average value is taken as the number of cell bubbles.

[0012] In the present invention, the average thickness t of the sealant layer is preferably in the range of 5 mm to 30 mm. When the average thickness t of the sealant layer is in the above range, it is possible to improve the balance between sealing performance and noise reduction.

[0013] In the present invention, it is preferable that the peak temperature of the sealant's tan δ is in the range of -120°C to -20°C, and that the peak value of the sealant's tan δ is 1.5 or greater. By ensuring that the peak temperature and value of the sealant's tan δ are within the above ranges, vibrations during driving can be attenuated, thereby effectively improving quietness. More specifically, when the frequency (500 Hz to 3000 Hz) of vibrations associated with road noise generated in a tire during driving is converted to a temperature range based on the temperature-frequency conversion rule, the temperature range is approximately -120°C to -20°C. If the sealant's peak value of tan δ is high and its viscosity is high in this temperature range, it can effectively attenuate vibrations associated with road noise during driving. The temperature-frequency conversion rule converts frequency into temperature, utilizing the fact that the viscoelastic behavior of a material changes by a constant factor depending on temperature. The loss tangent tan δ is measured using a viscoelasticity spectrometer in accordance with JIS-K6394 under conditions of a frequency of 10 Hz, an initial strain of 10%, and a dynamic strain of ±2%.

[0014] In the present invention, the silicone-based composition is preferably a two-component curing silicone. Two-component curing silicone allows the circumferential portions of the sealant strip to blend together easily during the curing reaction process, maintaining good sealing properties after curing. Furthermore, two-component curing silicone has low viscosity immediately after mixing the two components, allowing it to be applied even at low temperatures.

[0015] In the present invention, when a plurality of belt layers including belt cords inclined with respect to the tire circumferential direction and arranged so that the belt cords cross each other between layers are embedded in the tread portion, it is preferable that the sealant layer be arranged over an area wider than the narrowest belt layer among the plurality of belt layers. By arranging the sealant layer over an area wider than the narrowest belt layer, good sealing properties can be ensured. [Brief explanation of the drawings]

[0016] [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 a cross-sectional view showing a sealant layer formed on the inner surface of the pneumatic tire of FIG. 1. FIG. [Figure 3] 1 is a graph showing the relationship between the temperature and tan δ of the sealant of the present invention. [Figure 4] 2 is a cross-sectional view illustrating a method for manufacturing the pneumatic tire of FIG. 1. [Figure 5] 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. DETAILED DESCRIPTION OF THE INVENTION

[0017] The configuration of the present invention will be described in detail below with reference to the accompanying drawings. Fig. 1 shows a pneumatic tire according to an embodiment of the present invention, and Fig. 2 shows a sealant layer formed on the inner surface of the pneumatic tire.

[0018] 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.

[0019] 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.

[0020] 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. The multiple belt layers 7 include a belt layer 7A located on the innermost side in the tire radial direction and a belt layer 7B located outside the belt layer 7A, and the width of the belt layer 7A is wider than the width of the belt layer 7B. 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.

[0021] 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).

[0022] 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.

[0023] In the above-described pneumatic tire, 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. The sealant of the sealant layer 20 is composed of a silicone-based composition. The silicone-based composition contains a synthetic polymer compound having a main skeleton formed by siloxane bonds. As shown in FIG. 2, the sealant layer 20 has a porous structure. The porous structure of the sealant layer 20 includes closed cells 22 (shaded areas) that do not communicate with the tire cavity and open cells 23 (non-shaded areas) that communicate with the tire cavity. One example of a method for forming a porous structure is to mix and disperse a foaming agent in the sealant, and generate bubbles by thermal decomposition or chemical reaction of the foaming agent.

[0024] In the pneumatic tire described above, a sealant layer 20 is formed on the tire inner surface 10 in the tread portion 1, and since the sealant layer 20 has a porous structure, the sealant layer 20 not only exhibits good sealing properties but also contributes to improved noise reduction due to its porous structure. That is, during normal driving, the sealant layer 20, which has a porous structure, exhibits a sound-absorbing effect, and in the event of a puncture, the air bubbles in the sealant layer 20 collapse due to the pressure difference between the inside and outside of the tire, allowing the sealant to flow into the puncture hole and exhibit excellent sealing properties. In particular, a sealant made from a silicone-based composition has superior shape stability when cured compared to a sealant made from a butyl-based rubber, and therefore can maintain its porous structure even during driving, thereby effectively improving noise reduction.

[0025] In the above-described pneumatic tire, the porous structure of the sealant layer 20 includes closed cells 22 and open cells 23, and the open cell percentage Co, calculated from the total volume Vc of the closed cells 22 and the total volume Vo of the open cells 23, is preferably in the range of 30% to 80%. Having the open cell percentage Co in the above range allows for a well-balanced improvement in sealing performance and noise reduction. If the open cell percentage Co is less than 30%, the improvement in noise reduction is reduced, while if it exceeds 80%, the improvement in sealing performance is reduced. It is particularly desirable for the open cell percentage Co to be in the range of 50% to 70%.

[0026] In the above pneumatic tire, the density δ of the sealant layer 20 is 20 kg / m 3 ~200kg / m 3 When the density δ of the sealant layer 20 is in the above range, it is possible to improve the balance between sealing performance and noise reduction. 3 If it is less than 200 kg / m, the percentage of air bubbles will be high, and the effect of improving the sealing property will decrease. 3 If the density δ of the sealant layer 20 is more than 40 kg / m, the occupancy rate of the air bubbles is low, and the effect of improving noise reduction is reduced. 3 ~150kg / m 3 It is desirable that the temperature is in the range of

[0027] In the above pneumatic tire, the number of cell counts n contained in the sealant layer 20 is preferably in the range of 20 cells / 25 mm to 100 cells / 25 mm. Basically, the larger the number of cell count n, the more advantageous it is for noise reduction. By having the number of cell count n contained in the sealant layer 20 in the above range, noise reduction can be improved without increasing manufacturing costs. Here, if the number of cell count n contained in the sealant layer 20 is less than 20 cells / 25 mm, the noise reduction improvement effect decreases, and conversely, if it exceeds 100 cells / 25 mm, processing becomes difficult, increasing manufacturing costs. In particular, the number of cell count n contained in the sealant layer 20 is preferably in the range of 30 cells / 25 mm to 100 cells / 25 mm.

[0028] In the above pneumatic tire, the average thickness t of the sealant layer 20 is preferably in the range of 5 mm to 30 mm (see FIG. 2). By having the average thickness t of the sealant layer 20 in the above range, it is possible to improve the sealing performance and noise reduction in a well-balanced manner. Here, if the average thickness t of the sealant layer 20 is less than 5 mm, the effect of improving the sealing performance is reduced, and conversely, if it exceeds 30 mm, it becomes difficult to maintain the shape of the porous structure, and the effect of improving the noise reduction is reduced. In particular, it is desirable that the average thickness t of the sealant layer 20 is in the range of 10 mm to 20 mm.

[0029] Figure 3 shows the relationship between the temperature and tangent δ of the sealant layer in the present invention. As shown in Figure 3, the peak temperature Tp of tangent δ of the sealant layer 20 is in the range of -120°C to -20°C, and the peak value Vp of tangent δ of the sealant layer 20 is 1.5 or more. The peak temperature Tp and peak value Vp of tangent δ of the sealant layer 20 can be adjusted based on, for example, the degree of crosslinking of the sealant or the amount of liquid polymer added to the sealant. Examples of liquid polymers include liquid polybutene, liquid isobutene, liquid polyisoprene, liquid polybutadiene, liquid poly-α-olefin, liquid ethylene-propylene copolymer, and liquid ethylene-butylene copolymer.

[0030] As described above, when the peak temperature Tp of tan δ of the sealant layer 20 is in the range of −120°C to −20°C and the peak value Vp of tan δ of the sealant layer 20 is 1.5 or more, vibrations during driving can be damped, thereby effectively improving quietness. If the peak temperature Tp of tan δ of the sealant layer 20 is outside the above range, the effect of improving quietness decreases. In particular, it is desirable that the peak temperature Tp of tan δ of the sealant layer 20 is in the range of −90°C to −60°C. If the peak value Vp of tan δ of the sealant layer 20 is less than 1.5, the effect of improving quietness decreases. There are no particular limitations on the upper limit of the peak value Vp of tan δ of the sealant layer 20, but it may be, for example, 3.0 or less.

[0031] In the above pneumatic tire, the tan δ(V 100 ) is preferably in the range of 0.2 to 0.6. This optimizes the flow characteristics of the sealant layer 20 during running, and allows the sealant layer 20 to maintain good sealing properties and flow resistance. If the tan δ at 100°C of the sealant layer 20 is less than 0.2, the effect of improving the sealing properties is reduced, and conversely, if it is greater than 0.6, the flow resistance is reduced.

[0032] The above-described pneumatic tire can be manufactured by the following method. First, a pneumatic tire having a tread portion 1, a pair of sidewall portions 2, and a pair of bead portions 3 is manufactured as described above. Next, a sealant made of, for example, a silicone-based composition is applied to the tire inner surface 10 of the tread portion 1 to form a sealant layer 20. At this time, a foaming agent is dispersed in the sealant to give the sealant layer 20 a porous structure.

[0033] FIG. 4 shows a specific manufacturing method for the pneumatic tire of FIG. 1, and FIG. 5 shows a sealant layer formed on the tire inner surface in the tread portion. In FIG. 4, 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 in the axial direction of the tire 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 FIG. 5). 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] In the above pneumatic tire, when multiple belt layers 7 are embedded in the tread portion 1, the multiple belt layers 7 including belt cords inclined with respect to the tire circumferential direction and arranged so that the belt cords cross each other between the layers, it is preferable that the sealant layer 20 be arranged over an area wider than the narrowest belt layer 7B of the multiple belt layers 7, as shown in Fig. 1. In Fig. 1, the sealant layer 20 is arranged so as to protrude outward in the tire width direction from both edge portions Eb, Eb of the belt layer 7B in the tire width direction. By arranging the sealant layer 20 over an area wider than the narrowest belt layer 7B, good sealing properties can be ensured. [Example]

[0040] In a pneumatic tire having a tire size of 255 / 40R21 and equipped with a tread portion, a pair of sidewall portions, and a pair of bead portions, a sealant layer was formed on the inner surface of the tire in the tread portion, and tires of Conventional Example, Comparative Examples 1-2, and Examples 1-15 were produced with various variations in the constituent material of the sealant layer, the presence or absence of a porous structure in the sealant layer, the open cell ratio Co of the sealant layer, the density δ of the sealant layer, the number of cell cells n of the sealant layer, the average thickness t of the sealant layer, the peak temperature of tan δ of the sealant, the peak value of tan δ of the sealant, and the ratio of the width of the sealant layer to the width of the narrowest belt layer, as shown in Tables 1 and 2.

[0041] These test tires were evaluated for noise reduction and sealing performance by the following test methods, and the results are shown in Tables 1 and 2.

[0042] Quiet: Each test tire was mounted on a 21x9.0J rim wheel, inflated to 270kPa, and mounted on an SUV (2000cc displacement). The vehicle was driven at a speed of 100km / h on a paved road, and the road noise was evaluated by the driver. The evaluation results were expressed as an index, with the conventional tire being set at 100. The higher the index value, the better the quietness.

[0043] Sealability: Each test tire was mounted on a wheel with a rim size of 21 x 9.0J, the initial air pressure was set to 270 kPa, a 4.0 mm diameter nail was driven into the tread, the nail was removed, and the tire was left for one hour under a load of 100% of its maximum load capacity, after which the air pressure was measured again. The evaluation results are shown as follows: an air pressure of 240 kPa or more is indicated by "◎", an air pressure of 200 kPa or more but less than 240 kPa is indicated by "◯", an air pressure of 150 kPa or more but less than 200 kPa is indicated by "△", and an air pressure of less than 150 kPa is indicated by "X".

[0044] [Table 1]

[0045] [Table 2]

[0046] As can be seen from Tables 1 and 2, the tires of Examples 1 to 15 were able to ensure good sealing properties and improve noise reduction compared to the conventional tires. In contrast, the tire of Comparative Example 1 used a sealant made of diene rubber, so no improvements in sealing properties and noise reduction were achieved. Furthermore, the tire of Comparative Example 2 did not have a porous sealant layer, so no improvements in noise reduction were achieved.

[0047] The present disclosure encompasses the following inventions [1] to [8]. 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 is formed on the inner surface of the tire in the tread portion, the sealant of the sealant layer being composed of a silicone-based composition, and the sealant layer has a porous structure. Invention [2] is the pneumatic tire according to invention [1], characterized in that the porous structure of the sealant layer contains closed cells and open cells, and the open cell percentage Co, calculated from the total volume Vc of the closed cells and the total volume Vo of the open cells as Co = Vo / (Vc + Vo) × 100%, is in the range of 30% to 80%. Invention [3] is a method for manufacturing a sealant layer having a density δ of 20 kg / m 3 ~200kg / m 3 The pneumatic tire according to the invention [1] or [2] is characterized in that the range of Invention [4] is a pneumatic tire according to any one of inventions [1] to [3], characterized in that the number n of air cells contained in the sealant layer is in the range of 20 cells / 25 mm to 100 cells / 25 mm. Invention [5] is the pneumatic tire according to any one of inventions [1] to [4], characterized in that the average thickness t of the sealant layer is in the range of 5 mm to 30 mm. Invention [6] is a pneumatic tire according to any one of inventions [1] to [5], characterized in that the peak temperature of tan δ of the sealant is in the range of -120°C to -20°C, and the peak value of tan δ of the sealant is 1.5 or more. Invention [7] is the pneumatic tire according to any one of inventions [1] to [6], characterized in that the silicone composition is a two-component curing silicone. Invention [8] is a tire in which a plurality of belt layers are embedded in the tread portion, the belt layers including belt cords inclined with respect to the tire circumferential direction and arranged so that the belt cords cross each other between the layers, The pneumatic tire according to any one of inventions [1] to [7] is characterized in that the sealant layer is disposed in an area wider than the narrowest belt layer among the plurality of belt layers. [Explanation of symbols]

[0048] 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 22 Closed bubbles 23 Open bubbles

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 characterized in that a sealant layer is formed on the inner surface of the tire in the tread portion, the sealant of the sealant layer being composed of a silicone-based composition, and the sealant layer having a porous structure.

2. 2. The pneumatic tire according to claim 1, wherein the porous structure of the sealant layer includes closed cells and open cells, and an open cell percentage Co calculated from a total volume Vc of the closed cells and a total volume Vo of the open cells according to the equation Co = Vo / (Vc + Vo) × 100% is in the range of 30% to 80%.

3. The density δ of the sealant layer is 20 kg / m 3 ~200 kg / m 3 3. The pneumatic tire according to claim 1, wherein the range is 0.1 to 1.

0.

4. 3. The pneumatic tire according to claim 1, wherein the number n of cells contained in the sealant layer is in the range of 20 cells / 25 mm to 100 cells / 25 mm.

5. 3. The pneumatic tire according to claim 1, wherein the sealant layer has an average thickness t in the range of 5 mm to 30 mm.

6. 3. The pneumatic tire according to claim 1, wherein the sealant has a peak tan δ temperature in the range of −120° C. to −20° C., and a peak tan δ value of the sealant is 1.5 or more.

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

8. a plurality of belt layers are embedded in the tread portion, the belt layers including belt cords inclined with respect to the tire circumferential direction and arranged so that the belt cords cross each other between the layers; 3. The pneumatic tire according to claim 1, wherein the sealant layer is disposed over an area wider than the narrowest belt layer among the plurality of belt layers.

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