Pneumatic tire and method for manufacturing the same

Abstract

To provide a pneumatic tire that avoids deterioration in tire performance which is caused by impact of heat at the time of formation of a sealant layer and can keep preferable sealability by the sealant layer, and to provide a method for manufacturing the same.SOLUTION: A pneumatic tire includes: a tread part 1 extending in a tire circumferential direction and forming an annular shape; a pair of sidewall parts 2 disposed on both sides of the tread part 1; and a pair of bead parts 3 disposed on tire radial insides of these sidewall parts 2, where a sealant layer 20 is formed in a tire inner surface 10 in the tread part 1; the sealant layer 20 includes a sealant constituted of a silicone-based composition; a belt layer 7 including a belt cord inclined relative to the tire circumferential direction is embedded in the tread part 1; and a distance L from the belt layer 7 to the sealant layer 20 is 10 mm or less in all the parts of the belt layer 7 positioned on the tire radial most-inside.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 a manufacturing method thereof. More specifically, the present invention relates to a pneumatic tire that can avoid deterioration of tire performance due to the influence of heat when forming the sealant layer, and can maintain good sealing properties provided by the sealant layer, and a manufacturing method thereof. [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). Such a sealant is applied to the inner surface of the tire in a state softened by heating to a high temperature (see, for example, Patent Document 4). More specifically, the sealant layer is formed by arranging a strip of the sealant, which has been softened by heating to a high temperature, in a spiral shape along the tire circumferential direction on the inner surface of the tire.

[0004] However, the sealant layer formed as described above has a problem that when a sealant heated to a high temperature is applied to the inner surface of the tire, the tire constituent members embedded in the tread portion are deteriorated due to the influence, and as a result, tire performance such as high-speed durability is deteriorated. Also, even if a sealant layer is provided on the inner surface of the tire in the tread portion, it is difficult to ensure good puncture sealing unless the sealant flows sufficiently into the belt layer when a foreign object such as a nail penetrates the tread portion. [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 and a manufacturing method thereof that can avoid deterioration of tire performance due to the influence of heat when forming a sealant layer and can maintain good sealing properties provided by the sealant layer. [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, a sealant layer is formed on the tire inner surface in the tread portion, and the sealant of the sealant layer is made of a silicone-based composition; A belt layer including a belt cord inclined with respect to the tire circumferential direction is embedded in the tread portion, and the distance L from the belt layer to the sealant layer at the innermost position in the tire radial direction is 10 mm or less at all points of the belt layer.

[0008] In order to achieve the above object, a method for manufacturing a pneumatic tire according to the present invention is a method for manufacturing the above-mentioned pneumatic tire, After manufacturing a pneumatic tire excluding the sealant layer, The present invention is characterized in that when a sealant made of a silicone-based composition is applied to the inner surface of the tire in the tread portion to form the sealant layer, the temperature of the sealant applied to the inner surface of the tire is lowered to less than 70°C. Effect of the Invention

[0009] In the present invention, since a sealant layer containing a sealant made of a silicone-based composition is formed on the tire inner surface in the tread portion, it is possible to lower the temperature of the sealant applied to the tire inner surface. For example, the temperature of the sealant applied to the tire inner surface can be lowered to less than 70°C. Therefore, it is possible to reduce the effect of heat on the tire and avoid deterioration of tire performance, such as high-speed durability. In addition, since 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, when a foreign object such as a nail penetrates the tread portion, the sealant can easily flow into the belt layer, and good puncture sealing properties can be ensured.

[0010] In the present invention, the silicone-based composition is preferably a two-component curing silicone, which has a low viscosity immediately after mixing the two components and can therefore be applied even at low temperatures.

[0011] In the present invention, the glass transition temperature of the sealant is preferably in the range of −120° C. to −40° C. By using a sealant with a low glass transition temperature, good puncture sealing properties can be ensured in a low-temperature environment.

[0012] In the present invention, the thickness of the sealant layer is preferably in the range of 2.0 mm to 5.0 mm, which can ensure puncture sealing performance while suppressing deterioration of rolling resistance due to an increase in tire weight and suppressing uneven distribution of the sealant layer due to flow of the sealant.

[0013] 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.

[0014] In the present invention, the sealant layer has a structure in which a strip of sealant is spirally arranged along the tire circumferential direction, and it is preferable that the inclination direction of the sealant strip with respect to the tire circumferential direction is in the opposite phase to the inclination direction of the belt cord of the belt layer located at the innermost side in the tire radial direction with respect to the tire circumferential direction. In a pneumatic tire, plysteer occurs due to the orientation of the belt cord of the belt layer, but the orientation of the sealant strip is also a cause of plysteer. Therefore, by making the inclination direction of the sealant strip with respect to the tire circumferential direction in the opposite phase to the inclination direction of the belt cord of the belt layer located at the innermost side in the tire radial direction with respect to the tire circumferential direction, it is possible to reduce plysteer.

[0015] In the present invention, the width of the sealant layer is preferably 90% or more of the width of the belt layer located at the innermost side in the tire radial direction. In particular, it is preferable that the end of the sealant layer is disposed on the outer side in the tire width direction than the end of the belt layer located at the innermost side in the tire radial direction. By making the width of the sealant layer sufficiently large, puncture of the pneumatic tire can be effectively prevented.

[0016] In the present invention, when a belt cover layer including organic fiber cords oriented in the tire circumferential direction on the outer peripheral side of the belt layer is embedded in the tread portion, it is preferable that the end of the sealant layer is disposed on the outer side in the tire width direction than the end of the belt cover layer. By making the width of the sealant layer sufficiently large, punctures of the pneumatic tire can be effectively prevented.

[0017] 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. [Brief description of the drawings]

[0018] [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] FIG. 2 is a plan view showing a belt layer, a belt cover layer, and a sealant layer of the pneumatic tire of FIG. 1. [Figure 4] 2 is a cross-sectional view showing a method for manufacturing the pneumatic tire of FIG. 1. [Diagram 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. [Figure 6] 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

[0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings, in which: Figures 1 to 3 show a pneumatic tire according to an embodiment of the present invention.

[0020] As shown in FIG. 1, the pneumatic tire of this embodiment includes a tread portion 1 extending circumferentially around the tire to form an annular shape, a pair of sidewall portions 2, 2 arranged on either side of the tread portion 1, and a pair of bead portions 3, 3 arranged radially inward of the sidewall portions 2.

[0021] A carcass layer 4 is fitted 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 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.

[0022] 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 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.

[0023] At least one belt cover layer 8 is arranged on the outer periphery of the belt layer 7, in order to improve high-speed durability, and is made of reinforcing cords arranged at an angle of, for example, 5° or less with respect to the tire circumferential direction. This belt cover layer 8 is preferably of a jointless structure in which a strip material made of at least one reinforcing cord aligned and rubber-coated is continuously wound at an angle of substantially 0° with respect to the tire circumferential direction. As the reinforcing cord of the belt cover layer 8, an organic fiber cord such as nylon or polyethylene terephthalate (PET) is preferably used.

[0024] The above-described tire internal structure shows a typical example of a pneumatic tire, but is not limited thereto. Various grooves including a plurality of main grooves 11 extending in the tire circumferential direction are formed in the tread portion 1.

[0025] In the above pneumatic tire, the sealant layer 20 is formed on the tire inner surface 10 in the tread portion 1 so as to be continuous in the tire circumferential direction. 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 shifted 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 the tire balance. As shown in FIG. 3, the sealant layer 20 has a structure in which a sealant strip 21 is spirally arranged along the tire circumferential direction. The sealant of the sealant layer 20 is composed of a silicone-based composition. The silicone-based composition includes a synthetic polymer compound having a main skeleton formed by a siloxane bond.

[0026] In the above pneumatic tire, a belt layer 7 (7A, 7B) including a belt cord inclined with respect to the tire circumferential direction is embedded in the tread portion 1. As shown in FIG. 2, in all parts of the belt layer 7A located at the innermost side in the tire radial direction, the distance L from the belt layer 7A to the sealant layer 20 is 10 mm or less.

[0027] In the above-mentioned pneumatic tire, since the sealant layer 20 containing the sealant made of a silicone-based composition is formed on the tire inner surface 10 in the tread portion 1, it is possible to lower the temperature of the sealant applied to the tire inner surface 10. For example, the temperature of the sealant applied to the tire inner surface 10 can be lowered below 70°C. Therefore, it is possible to reduce the effect of heat on the tire and avoid deterioration of tire performance, such as high-speed durability. In addition, since the distance L from the belt layer 7A to the sealant layer 20 is 10 mm or less at all points of the belt layer 7A located at the innermost side in the tire radial direction, when a foreign object such as a nail penetrates the tread portion 1, the sealant easily flows into the belt layer 7A, and good puncture sealing properties can be ensured. If there is a part 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 properties at that part will be insufficient.

[0028] The above-mentioned pneumatic tire can be manufactured by the following method. First, a pneumatic tire is manufactured as described above, which includes the tread portion 1, a pair of sidewall portions 2, and a pair of bead portions 3, and has the belt layer 7 and belt cover layer 8 embedded in the tread portion 1. Next, a sealant made of a silicone-based composition is applied to the tire inner surface 10 in the tread portion 1 to form a sealant layer 20.

[0029] FIG. 4 shows a specific manufacturing method of the pneumatic tire of FIG. 1, and FIG. 5 shows a sealant layer formed on the inner surface of the tire 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 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 tire axial direction while rotating the tire from a state in which the nozzle 34 is close to the inner surface 10 of the tire, the sealant strip 21 can be arranged in a spiral shape on the inner surface 10 of the tire while being inclined with respect to the tire circumferential direction Tc (see FIG. 5). 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.

[0030] In the above-mentioned pneumatic tire, a sealant layer 20 having a structure in which a sealant strip 21 is arranged spirally along the tire circumferential direction is formed on the tire inner surface 10 in the tread portion 1, and the sealant is composed of a silicone-based composition, so that the circumferential portions of the sealant strip 21 become easily compatible with each other in the curing reaction process of the silicone-based composition, and the integrity of the circumferential portions of the sealant strip 21 is improved, thereby improving the sealing property of the sealant layer 20. In addition, since the integrity of the circumferential portions of the sealant strip 21 is good, the sealant layer 20 is less likely to flow toward the center in the tire width direction due to the centrifugal force generated during tire rotation, which also contributes to improving the sealing property. Furthermore, when a silicone-based composition is used as the sealant of the sealant layer 20, there is an advantage that it has excellent weather resistance and has low temperature dependency of physical properties.

[0031] When using a sealant made of a rubber composition mainly containing butyl-based rubber, a sealant layer is formed by heating a strip of sealant, which has been softened by being heated to a high temperature, to a spiral shape in the circumferential direction of the tire on the inner surface of the tire. However, in the sealant layer formed in this manner, the sealant cools before the wrapped portions of the sealant strip become familiar with each other, and therefore the integrated nature of the wrapped portions of the sealant strip is poor, resulting in insufficient sealing by the sealant layer.

[0032] Since the silicone-based composition has 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 effect of heat on the tire and prevents deterioration of tire performance. If the temperature is 70°C or higher, the effect of heat on the tire increases, which causes deterioration of tire performance. In particular, it is preferable that the temperature of the sealant applied to the tire inner surface 10 is 35°C or lower. In addition, from the viewpoint of the fluidity of the silicone-based composition, the lower limit of the temperature of the sealant applied to the tire inner surface 10 is 20°C.

[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 can be, for example, moisture-curing silicone. Two-component curing silicone is composed of a first liquid and a second liquid, and a curing reaction starts 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 the two-component curing silicone is low immediately after mixing the two liquids, it can be applied even at low temperatures. In particular, it is preferable that the two-component curing silicone is one that takes 5 days or more to completely cure.

[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 (for example, 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 glass transition temperature of the sealant of the sealant layer 20 is preferably in the range of -120°C to -40°C. By using a sealant with a low glass transition temperature, good puncture sealing properties can be ensured in low temperature environments. If the glass transition temperature of the sealant is higher than -40°C, the puncture sealing properties in low temperature environments are reduced.

[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 ensures puncture sealing performance while suppressing deterioration of rolling resistance due to an increase in tire weight and suppressing uneven distribution of the sealant layer 20 due to the flow of the sealant. If the thickness S of the sealant layer 20 is smaller than 2.0 mm, the puncture sealing performance decreases, and conversely, if it is larger than 5.0 mm, the rolling resistance may deteriorate due to an increase in tire weight and uneven distribution of the sealant layer 20 may occur due to the flow of the sealant. The thickness S of the sealant layer 20 is the average thickness of the entire tire. The average thickness of the sealant layer 20 can be calculated from the measured values ​​at a total of 40 points by, for example, photographing the tire meridian cross section at eight points on the circumference of the tire using a CT scan, 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 inward 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, 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 radial direction to the sealant layer 20 satisfies the relationship S / L≧0.3. By making the thickness S of the sealant layer 20 sufficiently large relative to the distance L, good puncture sealing performance can be ensured. If the ratio S / L is less than 0.3, the puncture sealing performance is reduced.

[0038] In the above pneumatic tire, when the belt layer 7 (7A, 7B) including the belt cord inclined with respect to the tire circumferential direction is embedded in the tread portion 1 as shown in Fig. 3, it is preferable that the inclination direction of the sealant strip material 21 with respect to the tire circumferential direction is in the opposite phase to the inclination direction of the belt cord of the belt layer 7A located at the innermost side in the tire radial direction with respect to the tire circumferential direction. In a pneumatic tire, plysteer occurs due to the orientation of the belt cord of the belt layer 7, but the orientation of the sealant strip material 21 also causes plysteer. Therefore, by making the inclination direction of the sealant strip material 21 with respect to the tire circumferential direction in the opposite phase to the inclination direction of the belt cord of the belt layer 7A located at the innermost side in the tire radial direction with respect to the tire circumferential direction, it is possible to reduce plysteer.

[0039] In the above 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 preferably that the end of the sealant layer 20 is disposed on the outer side 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 of 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 7A, the puncture sealing performance is reduced.

[0040] For the same reason, when a belt cover layer 8 containing organic fiber cords oriented in the tire circumferential direction on the outer circumferential side of the belt layer 7 is embedded in the tread portion 1, it is preferable that the end of the sealant layer 20 is disposed on the outer side in the tire width direction than the end 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.

[0041] FIG. 6 shows a pneumatic tire according to another embodiment of the present invention. In FIG. 6, 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. EXAMPLES

[0042] In a pneumatic tire having a tire size of 255 / 45R19 and including a tread portion, a pair of sidewall portions, and a pair of bead portions, a sealant layer having a structure in which a sealant strip is spirally arranged along the tire circumferential direction was formed on the tire inner surface of the tread portion, and tires of Comparative Examples 1-2 and Examples 1-6 were manufactured with variously different constituent materials of the sealant layer, thickness S of the sealant layer, ratio of the width of the sealant layer to the width of the belt layer, inclination direction of the sealant strip, distance L from the belt layer located at the innermost position in the tire radial direction to the sealant layer, and ratio S / L as shown in Table 1. In addition, a conventional tire not provided with a sealant layer on the tire inner surface of the tread portion was prepared.

[0043] Regarding the inclination direction of the sealant strip, when the inclination direction of the sealant strip with respect to the tire circumferential direction is in phase with the inclination direction of the belt cord of the belt layer located at the innermost side in the tire radial direction, the inclination direction is indicated as "same phase," and when the inclination direction of the sealant strip with respect to the tire circumferential direction is in opposite phase with the inclination direction of the belt cord of the belt layer located at the innermost side in the tire radial direction, the inclination direction is indicated as "opposite phase."

[0044] These test tires were evaluated for rolling resistance, high-speed durability, plysteer, and puncture sealing performance by the following test methods. The results are shown in Table 1.

[0045] Rolling resistance: Each test tire was mounted on a wheel with a rim size of 19 x 8.5J and attached to a rolling resistance tester, and the rolling resistance was measured in accordance with JIS-D4234 at an air pressure of 210kPa. The evaluation results were expressed as an index using the reciprocal of the measured value, with the conventional example being set at 100. The higher the index value, the lower the rolling resistance.

[0046] Fast durability: Each test tire was mounted on a wheel with a rim size of 19 x 8.5J, the air pressure was set to 360kPa, and the tire was mounted on an indoor drum testing machine (drum diameter 1707mm). The ambient temperature was controlled at 38±3°C, and the tire was loaded with 88% of the maximum JATMA load. The running speed was increased from 120km / h in increments of 10km / h, and the tire was run for 20 minutes at each speed, and the running distance until the tire was destroyed was measured. The evaluation results were expressed as an index with the conventional example being 100. The higher the index value, the better the high-speed durability.

[0047] Pricetea: Each test tire was mounted on a wheel with a rim size of 19 x 8.5J and attached to a uniformity tester, and the plysteer was measured in accordance with JIS-D4233 at an air pressure of 200kPa. The evaluation results were expressed as an index using the reciprocal of the measured value, with the conventional example being set at 100. The higher the index value, the smaller the plysteer.

[0048] Puncture sealing: 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, the nail was removed, and the tire was left for one hour, after which the air pressure was measured again and the rate of pressure drop from the initial air pressure was calculated. The evaluation results are shown as follows: if the pressure drop rate was 2% or less, it is indicated with "◎", if the pressure drop rate was more than 2% and less than 7%, it is indicated with "○", if the pressure drop rate was more than 7% and less than 20%, it is indicated with "△", and if the pressure drop rate was more than 20%, it is indicated with "X".

[0049] [Table 1]

[0050] As can be seen from Table 1, all of the tires of Examples 1 to 6 had good puncture sealing properties and maintained good high-speed durability. In contrast, the tire of Comparative Example 1 had a sealant layer containing a sealant mainly made of butyl rubber, and therefore the high-speed durability was deteriorated due to the influence of heat generated when forming the sealant layer, and the puncture sealing properties of the sealant layer were insufficient. In addition, the tire of Comparative Example 2 had insufficient puncture sealing properties of the sealant layer because the distance L from the belt layer located at the innermost side in the tire radial direction to the sealant layer was too large.

[0051] The present disclosure includes the following inventions [1] to

[12] . The invention [1] relates to 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 sealant layer is formed on the tire inner surface in the tread portion, and the sealant of the sealant layer is made of a silicone-based composition; The pneumatic tire is 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 at all points of the belt layer located at the innermost side in the tire radial direction is 10 mm or less. Invention [2] is the pneumatic tire according to invention [1], characterized in that the silicone-based composition is a two-component curing silicone. The invention [3] is the pneumatic tire according to the invention [1] or [2], characterized in that the glass transition temperature of the sealant is in the range of -120°C to -40°C. The invention [4] is the pneumatic tire according to any one of the inventions [1] to [3], wherein the thickness of the sealant layer is in the range of 2.0 mm to 5.0 mm. Invention [5] is a pneumatic tire according to any one of inventions [1] to [4], characterized in that the ratio of a thickness S of the sealant layer to a distance L from a belt layer located at the innermost side in the tire radial direction to the sealant layer satisfies the relationship S / L ≧ 0.3. Invention [6] is a pneumatic tire according to any one of inventions [1] to [5], characterized in that the sealant layer has a structure in which a strip of the sealant is spirally arranged along the tire circumferential direction, and the inclination direction of the sealant strip with respect to the tire circumferential direction is in opposite phase to the inclination direction of the belt cord of the belt layer located at the innermost side in the tire radial direction with respect to the tire circumferential direction. Invention [7] is a pneumatic tire according to any one of inventions [1] to [6], characterized in that the width of the sealant layer is 90% or more of the width of the belt layer located at the innermost side in the tire radial direction. Invention [8] is a pneumatic tire according to invention [7], characterized in that an end of the sealant layer is positioned outer in the tire width direction than an end of a belt layer located at the innermost side in the tire radial direction. Invention [9] is the pneumatic tire according to invention [8], characterized in that a belt cover layer including organic fiber cords oriented in the tire circumferential direction on the outer circumferential side of the belt layer is embedded in the tread portion, and an end of the sealant layer is positioned outward in the tire width direction than an end of the belt cover layer. Invention

[10] is a pneumatic tire according to any one of inventions [1] to [9], characterized in that a sound-absorbing material is provided along the tire circumferential direction on the radially inner side of the sealant layer. The invention

[11] is a method for producing a pneumatic tire according to any one of the inventions [1] to [9], After manufacturing a pneumatic tire excluding the sealant layer, This is a method for manufacturing a pneumatic tire, characterized in that when a sealant made of a silicone-based composition is applied to the inner surface of the tire in the tread portion to form the sealant layer, the temperature of the sealant applied to the inner surface of the tire is lowered to below 70°C. Invention

[12] is a manufacturing method for a pneumatic tire according to invention

[11] , 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. [Explanation of symbols]

[0052] 1 Tread section 2 Sidewall 3 Bead section 4 Carcass layer 5 Bead Core 6 Bead Filler 7 Belt layer 8 Belt cover layer 10 Tire inner surface 20 Sealant Layer 21 Sealant Strip 40 Sound absorbing material

Claims

1. A pneumatic tire 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 sealant layer is formed on the tire inner surface in the tread portion, and the sealant of the sealant layer is made of a silicone-based composition, 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 at all points of the belt layer located at the innermost side in the tire radial direction is 10 mm or less.

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

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

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

5. 3. The pneumatic tire according to claim 1, wherein a ratio of a thickness S of the sealant layer to a distance L from a belt layer located at the innermost side in the tire radial direction to the sealant layer satisfies a relationship of S / L≧0.

3.

6. 3. The pneumatic tire according to claim 1, wherein the sealant layer has a structure in which a strip of the sealant is spirally arranged along the tire circumferential direction, and an inclination direction of the strip of the sealant with respect to the tire circumferential direction is in opposite phase to an inclination direction of a belt cord of a belt layer located at the innermost side in the tire radial direction with respect to the tire circumferential direction.

7. 3. The pneumatic tire according to claim 1, wherein a width of the sealant layer is 90% or more of a width of a belt layer located at the innermost side in the tire radial direction.

8. The pneumatic tire according to claim 7, wherein an end portion of the sealant layer is disposed on the outer side in the tire width direction than an end portion of a belt layer positioned on the innermost side in the tire radial direction.

9. 9. The pneumatic tire according to claim 8, wherein a belt cover layer including organic fiber cords oriented in the tire circumferential direction on an outer circumferential side of the belt layer is embedded in the tread portion, and an end of the sealant layer is disposed outside in the tire width direction relative to an end of the belt cover layer.

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

11. 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.

12. The method for manufacturing a pneumatic tire according to claim 11, characterized in that a sound absorbing material is provided along a circumferential direction of the tire on an inner side in a radial direction of the tire of the sealant layer.

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