Pneumatic tire and manufacturing method therefor

Abstract

Provided are: a pneumatic tire that uses a release agent to prevent vulcanization failure while preventing a sealant layer from peeling off; and a manufacturing method therefor. The pneumatic tire comprises: a tread portion 1 that extends in the circumferential direction of the tire and forms an annular shape; a pair of sidewall portions 2 arranged on both sides of the tread portion 1; and a pair of bead portions 3 arranged on the inner sides of the sidewall portions 2 in the radial direction of the tire. In a pneumatic tire having a tire inner surface 10 coated with a release agent 16 containing particles 15, a sealant layer 20 is formed on the tire inner surface 10 in the tread portion 1, a sealant in the sealant layer 20 is composed of a silicone-based composition, and the particles 15 applied to an area for arranging the sealant layer 20 are spread into the sealant layer 20.

Description

Pneumatic tire and manufacturing method thereof

[0001] The present invention relates to a pneumatic tire having a sealant layer on the inner surface of the tire in the tread portion, and a manufacturing method thereof. More specifically, the present invention relates to a pneumatic tire that can prevent vulcanization failure by using a release agent while suppressing peeling of the sealant layer, and a manufacturing method thereof.

[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-based rubber (see, for example, Patent Documents 1 to 3). Examples of butyl-based rubber include butyl rubber (IIR) and halogenated butyl rubbers such as brominated butyl rubber (Br-IIR) and chlorinated butyl rubber (Cl-IIR).

[0004] However, when manufacturing pneumatic tires, a release agent containing particles such as talc or mica is applied to the inner surface of an unvulcanized tire. This release agent remains on the tire's inner surface after vulcanization, resulting in the problem of the sealant layer easily peeling off from the tire's inner surface. For example, it is possible to remove the release agent remaining on the tire's inner surface before forming the sealant layer, but this is undesirable because it increases the number of steps and reduces productivity. Furthermore, instead of applying a release agent to the tire's inner surface, it is possible to prevent the release agent from adhering to the tire's inner surface by providing a release function to the bladder. However, this reduces the release function during continuous production of pneumatic tires, which could lead to vulcanization failures. Therefore, it is still necessary to apply a release agent to the inner surface of an unvulcanized tire, and it is inevitable that the release agent will remain on the tire's inner surface after vulcanization.

[0005] Japanese Patent No. 6583456 Japanese Patent No. 6620851 Japanese Patent No. 7319533

[0006] An object of the present invention is to provide a pneumatic tire that can prevent vulcanization failure by using a release agent while suppressing peeling of the sealant layer, and a method for manufacturing the same.

[0007] In order to achieve the above object, the pneumatic tire of the present invention comprises a tread portion extending circumferentially in a ring-like shape in the tire circumferential direction, a pair of sidewall portions arranged on both sides of the tread portion, and a pair of bead portions arranged radially inward of the sidewall portions, and the tire inner surface is coated with a particle-containing release agent, wherein a sealant layer is formed on the tire inner surface in the tread portion, the sealant in the sealant layer is made of a silicone-based composition, and the particles applied to the area where the sealant layer is arranged are mixed into the sealant layer.

[0008] In order to achieve the above object, the method for manufacturing a pneumatic tire of the present invention comprises the steps of: molding an unvulcanized tire corresponding to a pneumatic tire having a tread portion extending circumferentially in a tire ring-like shape, a pair of sidewall portions arranged on either side of the tread portion, and a pair of bead portions arranged radially inward of the sidewall portions; vulcanizing the unvulcanized tire in a state in which a particulate release agent is applied to the inner surface of the unvulcanized tire to manufacture a pneumatic tire; applying a sealant made of a silicone-based composition to the inner surface of the tire in the tread portion to form a sealant layer; and incorporating the particles applied to the area where the sealant layer is to be disposed into the sealant layer.

[0009] In the present invention, in a pneumatic tire having a particle-containing release agent applied to its inner surface, a sealant layer containing a sealant made of a silicone-based composition is formed on the tire's inner surface in the tread portion, and particles applied to the area where the sealant layer is disposed are mixed into the sealant layer. That is, after a pneumatic tire is manufactured by vulcanizing an unvulcanized tire with a particle-containing release agent applied to its inner surface, when a sealant made of a silicone-based composition is applied to the tire's inner surface in the tread portion to form a sealant layer, the particles applied to the area where the sealant layer is disposed are incorporated into the sealant layer. While particles are not incorporated into the sealant layer in a sealant made of a rubber composition primarily containing butyl rubber, a sealant made of a silicone-based composition acts to incorporate the particles contained in the release agent when the sealant layer is applied and cured. This prevents uneven distribution of release agent particles at the interface between the tire's inner surface and the sealant layer, thereby suppressing peeling of the sealant layer from the tire's inner surface. According to the present invention, it is possible to prevent vulcanization failures by using a release agent, and furthermore, since there is no need to remove the release agent from the inner surface of the tire, there is no reduction in productivity of pneumatic tires.

[0010] In the present invention, it is preferable that the release agent contains a silicone-based composition. By containing a silicone-based composition in the release agent, vulcanization failure can be effectively prevented, and further, the release agent made of the silicone-based composition is easily incorporated into the sealant layer containing the sealant also made of the silicone-based composition, so peeling of the sealant layer can be effectively suppressed.

[0011] In the present invention, the weight of the sealant layer is preferably at least 10 times the weight of the particles applied to the area where the sealant layer is disposed. By making the weight of the sealant layer sufficiently large relative to the weight of the particles, the particles can be easily incorporated into the sealant layer, thereby effectively preventing peeling of the sealant layer.

[0012] In the present invention, the silicone-based composition is preferably a two-component curing silicone. Two-component curing silicones have low viscosity immediately after mixing the two components, making them suitable for application at low temperatures. Furthermore, mixing the two components shortens the mixing time, and stabilizes (uniforms) the thickness of the sealant layer after curing.

[0013] 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, it is preferable that the distance L from the belt layer to the sealant layer be 10 mm or less at all points of the belt layer located at the innermost side in the tire radial direction, 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 puncture sealing performance.

[0014] In the present invention, it is preferable that the ratio of the thickness S of the sealant layer to the distance L from the belt layer located at the innermost side in the tire radial direction to the sealant layer satisfies the relationship S / L ≥ 0.3. By making the thickness S of the sealant layer sufficiently large relative to the distance L, good puncture sealing performance can be ensured.

[0015] In the present invention, it is preferable that a sound-absorbing material be provided along the tire circumferential direction on the tire radially inner side of the sealant layer. In this case, a sound-absorbing effect based on the sound-absorbing material can be obtained, while foreign matter can be prevented from adhering to the sealant layer.

[0016] Fig. 1 is a meridian cross-sectional view showing a pneumatic tire according to an embodiment of the present invention. Fig. 2 is a cross-sectional view showing a main portion of the pneumatic tire of Fig. 1. Fig. 3 is a cross-sectional view showing an enlarged inner liner layer, a release agent layer, and a sealant layer of the pneumatic tire of Fig. 1. Fig. 4 is a cross-sectional view showing a method for manufacturing the pneumatic tire of Fig. 1. Fig. 5 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. 6 is a meridian cross-sectional view showing a pneumatic tire according to another embodiment of the present invention.

[0017] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings, in which: Figures 1 to 3 show a pneumatic tire according to an embodiment of the present invention.

[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 disposed on both sides of the tread portion 1, and a pair of bead portions 3, 3 disposed radially inward of the sidewall portions 2.

[0019] A carcass layer 4 is mounted between the 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, 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 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.

[0021] At least one belt cover layer 8 is disposed on the outer periphery of the belt layer 7, with the aim of improving high-speed durability. The belt cover layer 8 has at least one reinforcing cord arranged at an angle of, for example, 5° or less relative to the tire circumferential direction. The belt cover layer 8 preferably has a jointless structure in which a strip of at least one reinforcing cord, which is 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 above-described tire internal structure shows a typical example of a pneumatic tire, but is not limited thereto. An inner liner layer 9 (air permeation prevention layer) is disposed inside the carcass layer 4 along the carcass layer 4. 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, as shown in FIG. 3 , a release agent 16 containing particles 15 is applied to the tire inner surface 10. In addition to the particles 15, the release agent 16 may optionally contain a silicone-based composition, a surfactant, etc. When applied to the inner surface of an unvulcanized tire, these components are dispersed in water, but the water has evaporated in the vulcanized tire. Examples of the particles 15 include talc, mica, carbon black, alumina, etc. The particles 15 are effective as a release component as long as they are powder-like, and can have a spherical, plate-like, rod-like, or other shape. The maximum dimension of the particles 15 is preferably 1 mm or less. Conductive particles 15 are preferred because they contribute to reducing the electrical resistance of the pneumatic tire.

[0024] 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 in 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. At least a portion of the particles 15 applied to the area where the sealant layer 20 is disposed are mixed into the sealant layer 20.

[0025] The above-described pneumatic tire can be manufactured by the following method. First, an unvulcanized tire corresponding to the pneumatic tire having the tread portion 1, a pair of sidewall portions 2, and a pair of bead portions 3 as described above, with the belt layer 7 and belt cover layer 8 embedded in the tread portion 1, is molded, and the unvulcanized tire is vulcanized with a release agent 16 containing particles 15 applied to the inner surface of the unvulcanized tire to manufacture a pneumatic tire. Next, a sealant made of a silicone-based composition is applied to the tire inner surface 10 in the tread portion 1 to form a sealant layer 20. As a result, the particles 15 applied to the area where the sealant layer 20 is to be disposed are incorporated into the sealant layer 20 when the sealant of the sealant layer 20 hardens after application.

[0026] In this manner, in a pneumatic tire in which a release agent 16 containing particles 15 is applied to the tire inner surface 10, a sealant layer 20 containing a sealant made of a silicone-based composition is formed on the tire inner surface 10 in the tread portion 1, and the particles 15 applied to the area where the sealant layer 20 is disposed are mixed into the sealant layer 20. This prevents the particles 15 of the release agent 16 from being unevenly distributed at the interface between the tire inner surface 10 and the sealant layer 20, and suppresses peeling of the sealant layer 20 from the tire inner surface 10. Furthermore, the use of the release agent 16 makes it possible to prevent vulcanization failure, and since there is no need to remove the release agent 16 from the tire inner surface 10, there is no reduction in the productivity of pneumatic tires.

[0027] In the pneumatic tire, it is desirable that the release agent 16 contains a silicone-based composition. By containing a silicone-based composition in the release agent 16, vulcanization failure can be effectively prevented, and further, the release agent 16 made of a silicone-based composition can be easily incorporated into the sealant layer 20 containing a sealant also made of a silicone-based composition, so peeling of the sealant layer 20 can be effectively suppressed.

[0028] In the above pneumatic tire, the weight of the sealant layer 20 is preferably 10 times or more the weight of the particles 15 applied to the area where the sealant layer 20 is disposed. By making the ratio of the weight of the sealant layer 20 to the weight of the particles 15 sufficiently large, the particles 15 are more easily incorporated into the sealant layer 20, thereby effectively preventing peeling of the sealant layer 20. Here, if the ratio of the weight of the sealant layer 20 to the weight of the particles 15 is less than 10 times, the particles 15 are less likely to be incorporated into the sealant layer 20. In particular, the ratio of the weight of the sealant layer 20 to the weight of the particles 15 is preferably 25 times or more, more preferably 50 times or more, with the upper limit being 110 times.

[0029] 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 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 spirally arranged 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.

[0030] In the pneumatic tire described above, a sealant layer 20 having a structure in which a sealant strip 21 is spirally arranged along the tire circumferential direction is formed on the tire inner surface 10 in the tread portion 1. Because the sealant is composed of a silicone-based composition, the circumferential portions of the sealant strip 21 are more easily integrated with each other during the curing reaction process of the silicone-based composition, improving the sealing performance of the sealant layer 20. Furthermore, because the circumferential portions of the sealant strip 21 are more easily integrated with each other, 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.

[0031] Since 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 be lower than 70°C. This reduces the thermal effect on the tire and prevents deterioration of tire performance. If this temperature is 70°C or higher, the thermal effect 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.

[0032] The silicone-based composition constituting the sealant of the sealant layer 20 can be either 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 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 and second components 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 at least five days to fully cure are preferred.

[0033] 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 at the time of use. Examples of two-component curing silicones include those described in Japanese Patent Publication No. 2018-503725 and Japanese Patent Publication No. 2022-550962. As a commercially available two-component curing silicone, for example, SST-2650 manufactured by Dow can be used.

[0034] In the above pneumatic tire, the glass transition temperature of the sealant in 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.

[0035] In the above-described 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 ensures puncture sealing performance while suppressing deterioration of rolling resistance due to increased tire weight and suppressing uneven distribution of the sealant layer 20 caused by sealant flow. Here, if the thickness S of the sealant layer 20 is less than 2.0 mm, puncture sealing performance will be reduced. Conversely, if the thickness S is greater than 5.0 mm, increased tire weight will result in deterioration of rolling resistance and uneven distribution of the sealant layer 20 due to sealant flow. The thickness S of the sealant layer 20 is the overall average thickness. The average thickness of the sealant layer 20 can be calculated, for example, by CT scanning eight tire meridian cross sections around the tire and measuring the thickness of the sealant layer 20 at five points in each image: the tire equator, outer edge positions (on both sides) 10 mm inward in the tire width direction from the edge of the sealant layer 20, and intermediate positions (on both sides) between the tire equator and the outer edge positions. This is a total of 40 measurements.

[0036] In the above-described pneumatic tire, as shown in Fig. 1, 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 be 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 is reduced.

[0037] 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.

[0038] In the above-described pneumatic tire, when belt layers 7 (7A, 7B) including belt cords inclined with respect to the tire circumferential direction are embedded in the tread portion 1 as shown in Fig. 2, it is preferable that the distance (shortest distance) L from the belt layer 7A located at the innermost side 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.

[0039] 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, puncture sealing performance deteriorates.

[0040] Figure 6 shows a pneumatic tire according to another embodiment of the present invention. In Figure 6, a sound-absorbing material 40 is installed 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 characteristics 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 effect of the sound-absorbing material 20 can be obtained while preventing foreign matter from adhering to the sealant layer 20.

[0041] In manufacturing a pneumatic tire with a tire size of 255 / 45R19 and including a tread portion, a pair of sidewall portions, and a pair of bead portions, the presence or absence of a release agent applied to the inner surface of the tire, the type of release agent, the constituent material of the sealant layer, the ratio of the weight of the sealant layer to the weight (20 g) of the particles applied to the sealant layer area, the thickness S of the sealant layer, the distance L from the belt layer located at the innermost side in the tire radial direction to the sealant layer, and the ratio S / L were varied as shown in Table 1 (Comparative Examples 1-2 and Examples 1-6). The formulation of the release agent is as shown in Table 2. Note that in Comparative Example 2, instead of applying a release agent to the surface of the tire, a release treatment was performed on the outer surface of the bladder of the tire vulcanizer.

[0042] These test tires were evaluated for vulcanization failure, peeling resistance, and puncture sealing performance by the following test methods. The results are also shown in Table 1.

[0043] Vulcanization failure: The incidence of vulcanization failure was determined when 400 test tires of each type were vulcanized continuously. The evaluation results were indicated by "◎" when the incidence of vulcanization failure was 0%, by "◯" when the incidence of vulcanization failure was more than 0% and less than 1%, by "△" when the incidence of vulcanization failure was 1% or more and less than 5%, and by "×" when the incidence of vulcanization failure was 5% or more.

[0044] Peeling: Each test tire was mounted on a wheel with a rim size of 19 x 8.5J and attached to an indoor drum testing machine (drum diameter 1707 mm), and the tire was driven 6000 km under the following conditions: ambient temperature controlled at 38±3°C, air pressure set to 120 kPa, load set to 120% of the maximum load capacity, and speed set to 80 km / h. After running for 6000 km, the sealant layer on the inner surface of the tire was observed. The evaluation results were indicated by "◎" when there was no lifting or misalignment of the sealant layer, "◯" when there was no lifting of the sealant layer and the misalignment was less than 5 cm, and "×" when there was lifting of the sealant layer or the misalignment was 5 cm or more.

[0045] Puncture sealing ability: Each test tire was mounted on a wheel with a rim size of 19 x 8.5J, the initial air pressure was set to 250 kPa, a nail with a diameter of 4.0 mm was driven into the tread portion, the nail was removed, and the tire was left for 1 hour after which the air pressure was measured again and the rate of pressure drop relative to the initial air pressure was determined. The evaluation results were indicated by "◎" when the pressure drop rate was 2% or less, "◯" when the pressure drop rate was more than 2% and 7% or less, "△" when the pressure drop rate was more than 7% and 20% or less, and "×" when the pressure drop rate was more than 20%.

[0046]

[0047]

[0048] As can be seen from Table 1, the tires of Examples 1 to 6 almost never experienced vulcanization failure, and peeling of the sealant layer was sufficiently suppressed. In contrast, the tire of Comparative Example 1 had a particulate release agent applied to the inner surface of the tire, and used a sealant made of butyl rubber, so peeling of the sealant layer was evident. Furthermore, the tire of Comparative Example 2 had a release treatment applied to the outer surface of the bladder, which prevented the use of a release agent, resulting in a high incidence of vulcanization failure during continuous vulcanization.

[0049] REFERENCE SIGNS LIST 1 tread portion 2 sidewall portion 3 bead portion 4 carcass layer 5 bead core 6 bead filler 7 belt layer 8 belt cover layer 9 inner liner layer 10 tire inner surface 15 particles 16 release agent 20 sealant layer 21 sealant strip 40 sound absorbing material

Claims

1. A pneumatic tire comprising a tread portion extending circumferentially in an annular shape, a pair of sidewall portions disposed on either side of the tread portion, and a pair of bead portions disposed radially inward of the sidewall portions, the tire inner surface being coated with a particle-containing release agent, the pneumatic tire being characterized in that a sealant layer is formed on the tire inner surface in the tread portion, the sealant in the sealant layer is made of a silicone-based composition, and the particles coated in the area where the sealant layer is disposed are mixed into the sealant layer.

2. The pneumatic tire according to claim 1, wherein the release agent contains a silicone-based composition.

3. The pneumatic tire according to claim 1 or 2, characterized in that the weight of the sealant layer is 10 times or more the weight of the particles applied to the area where the sealant layer is disposed.

4. The pneumatic tire according to any one of claims 1 to 3, characterized in that the silicone composition is a two-component curing silicone.

5. A pneumatic tire as described in any one of claims 1 to 4, characterized in that a belt layer including belt cords inclined relative to the tire circumferential direction is embedded in the tread portion, and the distance L from the belt layer located at the innermost side in the tire radial direction to the sealant layer is 10 mm or less at all points of the belt layer.

6. The pneumatic tire according to claim 5, characterized in that the ratio of the thickness S of the sealant layer to the distance L from the belt layer located at the innermost side in the tire radial direction to the sealant layer satisfies the relationship S / L≧0.

3.

7. A pneumatic tire according to any one of claims 1 to 6, characterized in that a sound absorbing material is provided along the circumferential direction of the tire on the radially inner side of the sealant layer.

8. A method for producing a pneumatic tire, comprising the steps of: molding an unvulcanized tire corresponding to a pneumatic tire having a tread portion extending circumferentially in a ring shape, a pair of sidewall portions arranged on either side of the tread portion, and a pair of bead portions arranged radially inward of the sidewall portions; vulcanizing the unvulcanized tire in a state in which a particulate-containing release agent is applied to the inner surface of the unvulcanized tire to produce a pneumatic tire; applying a sealant made of a silicone-based composition to the inner surface of the tire in the tread portion to form a sealant layer; and incorporating the particles applied to the area in which the sealant layer is disposed into the sealant layer.

9. The method for producing a pneumatic tire according to claim 8, characterized in that the release agent contains a silicone-based composition.

10. The method for manufacturing a pneumatic tire according to claim 8 or 9, characterized in that the weight of the sealant layer is 10 times or more the weight of the particles applied to the area where the sealant layer is disposed.

11. The method for producing a pneumatic tire according to any one of claims 8 to 10, characterized in that the silicone composition is a two-component curing type silicone.

12. A method for manufacturing a pneumatic tire as described in any one of claims 8 to 11, characterized in that a belt layer including belt cords inclined relative to the tire circumferential direction is embedded in the tread portion, and 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.

13. The method for manufacturing a pneumatic tire according to claim 12, characterized in that the ratio of the thickness S of the sealant layer to the distance L from the belt layer located at the innermost side in the tire radial direction to the sealant layer satisfies the relationship S / L ≧ 0.

3.

14. The method for manufacturing a pneumatic tire according to any one of claims 8 to 13, characterized in that a sound absorbing material is provided along the circumferential direction of the tire on the radially inner side of the sealant layer.

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