Pneumatic tire

Abstract

To provide a pneumatic tire which can secure sealability under a low temperature environment.SOLUTION: A pneumatic tire includes: an annular tread part 1 extending in a tire circumferential direction; a pair of side wall parts 2 located on both sides of the tread part 1; and a pair of bead parts 4 located on the inner sides of the side wall parts 2 in a tire radial direction. A sealant layer 20 is formed on an inner surface of the tire in the tread part 1, and a glass transition temperature of the sealant constituting the sealant layer 20 is equal to or lower than a glass transition temperature of a cap compound constituting the tread part 1.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 more specifically, to a pneumatic tire that makes it possible to ensure sealing performance even in a low-temperature environment. [Background technology]

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

[0003] Conventionally, the sealant constituting the sealant layer is generally a rubber composition mainly composed of butyl-based rubber (see, for example, Patent Documents 1 to 3). Examples of butyl-based rubber include butyl rubber (IIR) and halogenated butyl rubber such as brominated butyl rubber (Br-IIR) and chlorinated butyl rubber (Cl-IIR). In addition, 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), and therefore a large amount of liquid polymer is blended.

[0004] However, sealants containing a large amount of liquid polymer as described above tend to have a high glass transition temperature Tg, and therefore have the problem that sufficient sealing properties cannot be ensured in a low-temperature environment. In addition, there is a risk that the sealant may crack during driving, making it difficult to ensure the durability of the tire. [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 can ensure sealing performance even in a low-temperature environment. [Means for solving the problem]

[0007] The pneumatic tire of the present invention that achieves the above-mentioned object includes a tread portion extending circumferentially of the tire to form a ring, a pair of sidewall portions arranged on either side of the tread portion, and a pair of bead portions arranged on the radially inward side of the sidewall portions, wherein a sealant layer is formed on the inner surface of the tire in the tread portion, and the glass transition temperature of the sealant that constitutes the sealant layer is lower than or equal to the glass transition temperature of a cap compound that constitutes the tread portion. Effect of the Invention

[0008] In the pneumatic tire of the present invention, the glass transition temperature of the sealant constituting the sealant layer is equal to or lower than the glass transition temperature of the cap compound constituting the tread portion as described above, so that peeling of the sealant in a low-temperature environment can be prevented and sealing properties can be ensured. In the present invention, the "glass transition temperature" of each material (sealant, cap compound, and inner liner compound described below) is defined as the peak temperature when a graph of tan δ against the temperature of each material (temperature curve of tan δ) is drawn (tan δ can be measured using a viscoelasticity spectrometer with an initial strain of 10%, an amplitude of ±2%, and a frequency of 20 Hz).

[0009] In the present invention, it is preferable that the inner liner layer is adjacent to the outer peripheral side of the sealant layer in the tread portion, and the glass transition temperature of the sealant is lower than that of the inner liner compound constituting the inner liner layer. As described above, by setting the glass transition temperature of the sealant constituting the sealant layer not only lower than that of the cap compound constituting the tread portion, but also lower than that of the inner liner compound, the balance of the physical properties of the inner liner layer and the sealant layer is good, which is advantageous in preventing peeling of the sealant in a low temperature environment.

[0010] In the present invention, the glass transition temperature of the sealant is preferably −60° C. or lower. Setting the glass transition temperature of the sealant to a sufficiently low temperature in this manner is advantageous in preventing peeling of the sealant in a low-temperature environment and in ensuring sealing properties.

[0011] In the present invention, the sealant is preferably made of a silicone composition. In addition, the silicone composition is preferably a two-component curing silicone. A sealant made of a silicone composition has a low glass transition temperature, excellent weather resistance, and low temperature dependency of physical properties, so it is advantageous for preventing the sealant from peeling in a low-temperature environment and ensuring sealing properties. In particular, two-component curing silicone has a low viscosity immediately after mixing the two components, so it can be applied even at low temperatures.

[0012] In the present invention, it is preferable that the tan δ of the sealant at 100° C. is 0.5 or less, which can prevent the sealant from distorting during running and affecting the tire balance.

[0013] In the present invention, it is preferable that a belt layer including a belt cord inclined with respect to the tire circumferential direction is embedded in the tread portion, and it is preferable that the distance L from the belt layer to the sealant layer is 10 mm or less at all points of the belt layer located at the innermost side in the tire radial direction. This 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 puncture sealing performance.

[0014] In the present invention, it is preferable that a sound absorbing material is provided along the tire circumferential direction on the inner side in the tire radial direction of the sealant layer. In this case, the sound absorbing material can be provided on the sealant layer applied at a low temperature, so that damage to the sound absorbing material can be avoided and the sound absorbing effect can be well maintained.

[0015] In the pneumatic tire of the present invention, after manufacturing the pneumatic tire excluding the sealant layer, a sealant made of a silicone-based composition can be applied to the tire inner surface in the tread portion to form a sealant layer, and at that time, it is preferable to set the temperature of the sealant applied to the tire inner surface lower than 70° C. By lowering the temperature of the sealant applied to the tire inner surface in this manner, heat shrinkage of the belt cover layer due to heating during the formation of the sealant layer is suppressed, thereby reducing distortion occurring in the pneumatic tire and improving its durability. [Brief description 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. [Diagram 2] FIG. 2 is a cross-sectional view showing a main part of the pneumatic tire of FIG. [Diagram 3] 2 is a cross-sectional view showing a method for manufacturing the pneumatic tire of FIG. 1. [Figure 4] 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. [Diagram 5] FIG. 2 is a meridian cross-sectional view showing a pneumatic tire according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The configuration of the present invention will be described in detail below with reference to the accompanying drawings.

[0018] As shown in Fig. 1, the pneumatic tire of this embodiment includes a tread portion 1 that extends in the tire circumferential direction to form an annular shape, a pair of sidewall portions 2 disposed on both sides of the tread portion 1, and a pair of bead portions 3 disposed on the tire radially inward side of the sidewall portions 2. Although not depicted in Fig. 1 because it is a meridian cross section, the tread portion 1, the sidewall portions 2, and the bead portions 3 each extend in the tire circumferential direction to form an annular shape, thereby forming a basic toroidal structure of a pneumatic tire. The following explanation using Fig. 1 is basically based on the meridian cross section shown in the figure, but each tire component extends in the tire circumferential direction to form an annular shape.

[0019] A carcass layer 4 is fitted between a pair of bead portions 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 arranged in each bead portion 3. A bead filler 6 made of a rubber composition having a triangular cross section is arranged on the outer periphery of the bead core 5.

[0020] A plurality of 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 a plurality of belt cords inclined with respect to the tire circumferential direction, and are arranged so that the belt cords cross each other between 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. As the belt cords of the belt layers 7, steel cords are preferably used.

[0021] At least one belt reinforcing layer 8 is disposed on the outer periphery of the belt layer 7 for the purpose of improving high-speed durability. As the belt reinforcing layer 8, for example, as shown in the figure, two layers can be provided: a full cover that covers the entire width of the belt layer 7, and an edge cover that locally covers the end of the belt layer 7. The belt reinforcing layer 8 includes a reinforcing cord oriented in the tire circumferential direction. In the belt reinforcing layer 8, the reinforcing cord is set at an angle of, for example, 0° to 5° with respect to the tire circumferential direction. It is preferable that the belt reinforcing layer 8 has a jointless structure in which a strip material made of at least one reinforcing cord that is aligned and rubber-coated is continuously wound at substantially 0° with respect to the tire circumferential direction. As the reinforcing cord of the belt reinforcing layer 8, an organic fiber cord such as nylon or polyethylene terephthalate (PET) is preferably used.

[0022] An inner liner layer 9 is provided on the inner surface of the tire along the carcass layer 4. This inner liner layer 9 is a layer for preventing air filled in the tire from permeating to the outside of the tire. The inner liner layer 9 is composed of, for example, a rubber composition mainly composed of butyl rubber having air permeation prevention properties. Alternatively, it can be composed of a resin layer having a thermoplastic resin as a matrix. In the case of a resin layer, an elastomer component may be dispersed in a thermoplastic resin matrix.

[0023] In the tread portion 1, a tread rubber layer 11 is disposed on the outer peripheral side of the above-mentioned carcass layer 4, belt layer 7, and belt reinforcing layer 8. The tread rubber layer 11 may have a structure in which two types of rubber layers with different physical properties (a cap tread layer constituting the tread surface of the tread portion 1 and an under tread layer disposed on its inner peripheral side) are laminated in the tire radial direction. A side rubber layer 12 is disposed on the outer peripheral side (outside in the tire width direction) of the carcass layer 4 in the sidewall portion 2, and a rim cushion rubber layer 13 is disposed on the outer peripheral side (outside in the tire width direction) of the carcass layer 4 in the bead portion 3.

[0024] The above-described internal structure of a tire is a typical example of a pneumatic tire, and the tire of the present invention is not limited thereto. Various grooves such as multiple main grooves extending in the tire circumferential direction and lug grooves extending in the tire width direction can be formed in the tread portion 1.

[0025] In the above pneumatic tire, a sealant layer 20 is formed continuously in the tire circumferential direction on the tire inner surface (the inner peripheral side of the inner liner layer 9) in the tread portion 1. The sealant of the sealant layer 20 can be composed of a rubber composition mainly containing a butyl-based rubber or a silicone-based composition, and it is particularly preferable to use a silicone-based composition. As the butyl-based rubber, for example, in addition to butyl rubber (IIR), halogenated butyl rubber such as brominated butyl rubber (Br-IIR) and chlorinated butyl rubber (Cl-IIR) can be used. The silicone-based composition includes a synthetic polymer compound having a main skeleton formed by a siloxane bond.

[0026] The sealant constituting the sealant layer 20, whether it is composed of the above-mentioned rubber composition or silicone-based composition, is set so that its glass transition temperature is equal to or lower than the glass transition temperature of the cap compound constituting the tread portion 1, and preferably lower than the glass transition temperature of the cap compound. The cap compound refers to the rubber (vulcanized rubber) constituting the tread portion 1 (particularly the cap tread layer). Since the glass transition temperature of the sealant is low in this way, peeling of the sealant in a low-temperature environment can be prevented and sealing properties can be ensured.

[0027] The glass transition temperature of the sealant is preferably lower than the glass transition temperature of the capping compound and lower than the glass transition temperature of the inner liner compound constituting the inner liner layer 9. This provides a good balance of physical properties between the adjacent inner liner layer and sealant layer, which is advantageous in preventing peeling of the sealant in a low-temperature environment. The inner liner compound refers to the rubber (vulcanized rubber) or resin constituting the inner liner layer 9.

[0028] The glass transition temperature of the sealant may satisfy the above-mentioned relationship, but is preferably -60°C or lower, more preferably -90°C or lower, and even more preferably -90°C to -120°C. In this way, setting the glass transition temperature of the sealant to a sufficiently low temperature is advantageous for preventing the sealant from peeling off in a low-temperature environment and ensuring the sealability. If the glass transition temperature of the sealant exceeds -60°C, the effect of preventing the sealant from peeling off in a low-temperature environment and ensuring the sealability becomes limited. The glass transition temperature of the sealant can be set by adjusting the type and amount of liquid polymer (e.g., paraffin oil or aromatic oil) blended in the rubber composition or silicone-based composition constituting the sealant.

[0029] The glass transition temperatures of the cap compound and the inner liner compound are not particularly limited as long as they satisfy the above-mentioned relationship, but the glass transition temperature of the cap compound may be set to, for example, -20°C to -60°C, and the glass transition temperature of the inner liner compound may be set to, for example, -30°C to -60°C.

[0030] The sealant of the present invention not only has a glass transition temperature that satisfies the above relationship, but also has a tan δ at 100° C. that is preferably 0.5 or less, and more preferably 0.5 to 0.3. This can prevent the sealant layer 20 from distorting during running and affecting tire balance. If the tan δ at 100° C. of the sealant exceeds 0.5, the steering stability decreases.

[0031] The above-mentioned pneumatic tire can be manufactured by the following method. First, a pneumatic tire is manufactured, 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 the belt cover layer 8 are embedded in the tread portion 1, as described above. Next, a sealant is applied to the tire inner surface (the inner peripheral side of the inner liner layer 9) in the tread portion 1 to form a sealant layer 20. At that time, since the sealant satisfies the above-mentioned physical properties and has good fluidity even at low temperatures, the temperature of the sealant applied to the tire inner surface can be lowered to less than 70°C. This makes it possible to suppress the thermal shrinkage of the belt cover layer 8 caused by heating during the formation of the sealant layer 20. If this temperature is 70°C or higher, the distortion caused in the pneumatic tire increases, and durability deteriorates. In particular, it is desirable that the temperature of the sealant applied to the tire inner surface be 40°C or lower. From the viewpoint of fluidity at low temperatures, it is preferable that the sealant is made of a silicone-based composition. Also, from the viewpoint of fluidity of the silicone-based composition, the lower limit of the temperature of the sealant applied to the tire inner surface is preferably 20°C.

[0032] FIG. 3 shows a specific manufacturing method of the pneumatic tire of FIG. 1, and FIG. 4 shows the sealant layer 20 formed on the inner surface of the tire 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 from a nozzle 34 as a strip 21. This 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 inner surface of the tire, the strip 21 of sealant can be arranged in a spiral shape on the inner surface of the tire while being inclined with respect to the tire circumferential direction Tc (see FIG. 4). The spirally arranged sealant strip 21 has its circumferential portions in close contact with each other. The sealant strip 21 arranged in a spiral shape is integrated to form the sealant layer 20.

[0033] 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. One-component curing silicone is, for example, moisture-curing silicone. Two-component curing silicone is composed of a first liquid and a second liquid, and a curing reaction begins by mixing these first liquid and second liquid, and the stability of the sealant layer 20 is ensured after curing. In the above-mentioned device, the first liquid and the second liquid of the two-component curing silicone are supplied from pumps 32 and 33, respectively. Since the viscosity of two-component curing silicone is low immediately after mixing the two liquids, it can be applied even at low temperatures.

[0034] The two-component curing silicone is composed of, for example, a condensation curable silyl-terminated polymer, a silane crosslinking agent, a condensation catalyst, a filler, and the like. Examples of the condensation curable silyl-terminated polymer include polydialkylsiloxane, alkylphenylsiloxane, organic polymers having a silyl group (e.g., silyl polyether, silyl acrylate), and polyisobutylene having a silyl group. Examples of the silane crosslinking agent include alkoxy-functional silane, oximosilane, acetoxysilane, and enoxysilane. Examples of the filler include iron oxide, titanium dioxide, carbon black, and talc. Examples of the condensation catalyst include titanate and zirconate. These condensation curable silyl-terminated polymers, silane crosslinking agents, condensation catalysts, and fillers are stored in a state in which they are separated into a first liquid and a second liquid in a combination that does not cause a curing reaction to proceed, and are mixed when used.

[0035] In the above pneumatic tire, the width Ws of the sealant layer 20 is preferably 90% or more of the width Wb of the belt layer 7. By making the width Ws of the sealant layer 20 sufficiently larger than the width Wb of the belt layer 7, punctures in the pneumatic tire can be effectively prevented. Here, if the width Ws of the sealant layer 20 is smaller than 90% of the width Wb of the belt layer 7, the puncture sealing performance decreases.

[0036] In the above pneumatic tire, as shown in FIG. 2, the thickness S of the sealant layer 20 is preferably in the range of 2.0 mm to 5.0 mm. This can ensure puncture sealing performance while preventing deterioration of durability due to increased tire weight. If the thickness S of the sealant layer 20 is less than 2.0 mm, the puncture sealing performance decreases, and conversely, if it is greater than 5.0 mm, the durability may deteriorate due to increased tire weight. The thickness S of the sealant layer 20 is the overall average thickness. Such an average thickness of the sealant layer 20 can be calculated from the measured values ​​at a total of 40 points, for example, by photographing the tire meridian cross section at eight points on the tire circumference by CT scanning, and measuring the thickness of the sealant layer 20 at five points in each photographed image, namely, the tire equator position, the outer edge positions (both sides) 10 mm toward the inner side in the tire width direction from the edge of the sealant layer 20, and the intermediate positions (both sides) between the tire equator position and the outer edge position.

[0037] In the above pneumatic tire, as shown in Fig. 2, it is preferable that the distance (shortest distance) L from the belt layer 7 to the sealant layer 20 is 10 mm or less at all points of the belt layer 7 located at the innermost side in the tire radial direction. This makes it easier for the sealant to flow into the belt layer 7 when a foreign object such as a nail penetrates the tread portion 1, thereby ensuring good puncture sealing properties. If there is a part where the distance L from the belt layer 7 to the sealant layer 20 is greater than 10 mm, there is a risk that the puncture sealing properties at that part will be insufficient.

[0038] FIG. 5 shows a pneumatic tire according to another embodiment of the present invention. In FIG. 5, a sound-absorbing material 40 is provided along the tire circumferential direction on the tire radially inner side of the sealant layer 20. The sound-absorbing material 40 is made of a porous material having open cells, and has a predetermined sound-absorbing characteristic based on its porous structure. It is preferable to use foamed polyurethane as the porous material of the sound-absorbing material 40. The sound-absorbing material 40 is attached onto the sealant layer 20 based on the adhesiveness of the sealant layer 20 after the sealant layer 20 is formed. In this case, the sound-absorbing material 40 is provided on the sealant layer 20 applied at a low temperature, so that damage to the sound-absorbing material 40 can be avoided and its sound-absorbing effect can be well maintained.

[0039] The present invention will be further described below with reference to examples, but the scope of the present invention is not limited to these examples. EXAMPLES

[0040] Tires of Comparative Examples 1 to 3 and Examples 1 to 5 were manufactured with a tire size of 255 / 45R19, with different sealant formulations, cap compound types, and inner liner compound types as shown in Table 1. The formulations of the cap compounds and inner liner compounds are shown in Tables 2 and 3, and the numbers are listed in the column for the type of each material in Table 1. In all tires, the thickness S of the sealant layer was 3 mm, and the distance L from the belt layer to the sealant layer was 8 mm.

[0041] Table 1 also lists the glass transition temperature Tg (unit: °C) of each of the sealant, cap compound, and inner liner compound. The glass transition temperature Tg of each material is defined as the peak temperature when a graph of tan δ against temperature (temperature curve of tan δ) of each material is drawn, and tan δ was measured using a viscoelasticity spectrometer (manufactured by Toyo Seiki Seisakusho) with an initial strain of 10%, an amplitude of ±2%, and a frequency of 20 Hz.

[0042] Furthermore, Table 1 shows the tire destruction temperature (the test temperature used to evaluate the low-temperature sealability described later) measured by the following method.

[0043] Tire Destruction Temperature Each test tire was mounted on a wheel with a rim size of 8.5J, aired to 230 kPa, and attached to a test vehicle. The tire was then driven for 30 minutes at a speed of 60 km / h on a test road surface equipped with three φ9.5 mm cleats at a test temperature of 0°C. After that, the test temperature was lowered by 5°C every 30 minutes, and the tire was driven until it failed. The temperature at which the tire failed was recorded as the "tire failure temperature."

[0044] The low temperature sealability of these test tires was evaluated by the following test method, and the results are shown in Table 1.

[0045] Low temperature sealing Each test tire was mounted on a wheel with a rim size of 8.5J, the air pressure was set to 230kPa, and the tire was mounted on a test vehicle, and a nail with a diameter of 5mm was driven into the main groove of the tread under the "tire destruction temperature" conditions of each test tire, and the vehicle was driven at a speed of 60km / h with the nail still in place for one hour, after which the nail was removed and the tire was left to stand for 24 hours under the "tire destruction temperature" environment of each test tire, after which the air pressure was measured. The evaluation results were shown on a three-point scale as follows: 3: Air pressure after standing is 200kPa or more 2: Air pressure after standing is 150kPa or more and less than 200kPa 1: Air pressure after standing is less than 150kPa

[0046] [Table 1]

[0047] The types of raw materials used in Table 1 are shown below. Silicone rubber 1: Shin-Etsu Chemical Co., Ltd. KE-551-U Silicone rubber 2: Two-component curing silicone, DOW DOWSIL SE930 Butyl rubber: JSR CHLOROBUTYL1066 Paraffin oil: Kaneda Hi-Cole K-350 Aromatherapy oil: Idemitsu Kosan Diana Process Oil AH-58

[0048] [Table 2]

[0049] [Table 3]

[0050] The types of raw materials used in Tables 2 and 3 are shown below. NR: Natural rubber, SIR20 SBR1: Styrene butadiene rubber, Zeon Nipol 1502 SBR2: Styrene butadiene rubber, Zeon Nipol 9548 CB: Carbon black, Degussa-Huels Carbon Black N772 Adhesive: Yasuhara Chemical YS Resin PX1000 Butyl rubber: JSR CHLOROBUTYL1066 Process oil: Idemitsu Kosan Diana Process Oil NP250 Paraffin oil: Kaneda Hi-Col K-350 Sulfur: Tsurumi Chemical Industry Co., Ltd. Kinkaji Oil-filled Powdered Sulfur

[0051] As is clear from Table 1, Examples 1 to 5 exhibited excellent low-temperature sealing properties while preventing peeling of the sealant in a low-temperature environment. On the other hand, Comparative Examples 1 to 3 could not exhibit sufficient sealing properties in a low-temperature environment because the glass transition temperature of the sealant was higher than the glass transition temperature of the cap compound.

[0052] The present disclosure includes the following inventions. Invention [1] A pneumatic tire having a tread portion extending in a circumferential direction of the tire 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 radially inner side of the sidewall portions, A pneumatic tire comprising: a sealant layer formed on the inner surface of the tire in the tread portion; and a sealant constituting the sealant layer having a glass transition temperature lower than the glass transition temperature of a cap compound constituting the tread portion. Invention [2] A pneumatic tire as described in invention [1], characterized in that an inner liner layer is adjacent to the outer circumferential side of the sealant layer in the tread portion, and the glass transition temperature of the sealant is lower than the glass transition temperature of an inner liner compound constituting the inner liner layer. Invention [3] A pneumatic tire according to invention [1] or [2], characterized in that the glass transition temperature of the sealant is -60°C or lower. Invention [4] The invention [1] characterized in that the sealant is made of a silicone-based composition. The pneumatic tire according to any one of claims 1 to 3. Invention [5] The pneumatic tire according to invention [4], wherein the silicone-based composition is a two-component curing silicone. Invention [6] The pneumatic tire according to any one of inventions [1] to [5], wherein the sealant has a tan δ of 0.5 or less at 100°C. Invention [7] A pneumatic tire according to any one of inventions [1] to [6], characterized in that a belt layer including a belt cord inclined with respect to the tire circumferential direction is embedded in the tread portion, and a distance L from the belt layer to the sealant layer is 10 mm or less at all points of the belt layer located at the innermost side in the tire radial direction. Invention [8] The pneumatic tire according to any one of inventions [1] to [7], characterized in that a sound absorbing material is provided along the tire circumferential direction on the radially inner side of the sealant layer. Invention [9] A method for producing a pneumatic tire according to any one of Inventions [1] to [8], After manufacturing a pneumatic tire excluding the sealant layer, A method for manufacturing a pneumatic tire, comprising: applying a sealant made of a silicone-based composition to an inner surface of the tire in the tread portion to form the sealant layer, the method comprising the steps of: lowering a temperature of the sealant applied to the inner surface of the tire to less than 70°C. [Explanation of symbols]

[0053] 1 Tread section 2 Sidewall 3 Bead section 4 Carcass layer 5 Bead Core 6 Bead Filler 7 Belt layer 8 Belt cover layer 9 Inner liner layer 11 Tread rubber layer 12 Side rubber layer 13 Rim cushion rubber layer 20 Sealant Layer 40 Sound absorbing material

Claims

1. A pneumatic tire including 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, A pneumatic tire characterized in that a sealant layer is formed on the inner surface of the tire in the tread portion, and the glass transition temperature of the sealant constituting the sealant layer is lower than the glass transition temperature of a cap compound constituting the tread portion.

2. 2. The pneumatic tire according to claim 1, wherein an inner liner layer is adjacent to the outer circumferential side of the sealant layer in the tread portion, and the glass transition temperature of the sealant is lower than the glass transition temperature of an inner liner compound constituting the inner liner layer.

3. 3. The pneumatic tire according to claim 1, wherein the sealant has a glass transition temperature of −60° C. or lower.

4. 3. The pneumatic tire according to claim 1, wherein the sealant is made of a silicone-based composition.

5. 5. The pneumatic tire according to claim 4, wherein the silicone composition is a two-component curing silicone.

6. 3. The pneumatic tire according to claim 1, wherein the sealant has a tan δ at 100° C. of 0.5 or less.

7. 3. The pneumatic tire according to claim 1, wherein a belt layer including a belt cord inclined with respect to a tire circumferential direction is embedded in the tread portion, and a distance L from the belt layer to the sealant layer is 10 mm or less at all points of the belt layer located at the innermost side in the tire radial direction.

8. 3. The pneumatic tire according to claim 1, further comprising a sound absorbing material disposed along a circumferential direction of the tire on an inner side in a radial direction of the tire of the sealant layer.

9. A method for manufacturing the pneumatic tire according to claim 1 or 2, After manufacturing a pneumatic tire excluding the sealant layer, A method for manufacturing a pneumatic tire, comprising: applying a sealant made of a silicone-based composition to an inner surface of the tire in the tread portion to form the sealant layer, the method comprising the steps of: lowering a temperature of the sealant applied to the inner surface of the tire to less than 70°C.

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