Pneumatic Tire and Method for Producing the Same

Abstract

Provided are a pneumatic tire and a method for manufacturing the same that enable good retention of the sealing property by a sealant layer and further enable suppression of peeling of the sealant layer. In a tread portion 1, a plurality of belt layers 7 are embedded that include belt cords inclined with respect to the tire circumferential direction and are arranged such that the belt cords cross each other between the layers. The belt layers 7 include a first belt layer 7A located on the innermost side in the tire radial direction and a second belt layer 7B located on the outside thereof. A sealant layer 20 having a structure in which a strip material 21 of the sealant is spirally arranged along the tire circumferential direction is formed on the inner surface 10 of the tire in the tread portion 1. The sealant is composed of a silicone-based composition. When the angle θ formed by the belt cord of the first belt layer 7A and the belt cord of the second belt layer 7B is 110° or less, the inclination direction of the strip material 21 of the sealant is the same as the inclination direction of the belt cord of the first belt layer 7A. When the angle θ exceeds 110°, the inclination direction of the strip material 21 of the sealant is opposite to the inclination direction of the belt cord of the first belt layer 7A.

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 method for manufacturing the same. More specifically, the present invention relates to a pneumatic tire and a method for manufacturing the same that can maintain good sealing performance by the sealant layer and further suppress peeling of the sealant layer.

Background Art

[0002] In a pneumatic tire, it has been proposed to provide a sealant layer on the inner side in the tire radial direction of the inner liner layer in the tread portion. In such a pneumatic tire, when a foreign object such as a nail pierces the tread portion, the sealant flows into the through-hole, thereby suppressing a decrease in air pressure and enabling driving to be maintained.

[0003] Conventionally, as the sealant constituting the sealant layer, a rubber composition mainly composed of butyl rubber is generally used (see, for example, Patent Documents 1 to 3). Examples of butyl rubber include halogenated butyl rubbers such as brominated butyl rubber (Br-IIR) and chlorinated butyl rubber (Cl-IIR) in addition to butyl rubber (IIR). Such a sealant is applied to the inner surface of the tire in a state of being softened by heating to a high temperature (see, for example, Patent Document 4). More specifically, a sealant layer is formed by spirally arranging a strip material of the sealant in a softened state by heating to a high temperature along the tire circumferential direction on the inner surface of the tire.

[0004] However, in the sealant layer formed as described above, since the sealant cools down before the circumferential portions of the sealant strip material fit together, the integrality of the circumferential portions of the sealant strip material is not good. As a result, there is a problem that the sealing performance by the sealant layer becomes insufficient. In addition, if the integrality of the circumferential portions of the sealant strip material is insufficient, the sealant layer easily flows toward the center side of the tread portion due to the centrifugal force generated during tire rotation, which also causes a decrease in sealing performance.

Prior Art Documents

Patent Document

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0006] An object of the present invention is to provide a pneumatic tire capable of favorably maintaining the sealing property by a sealant layer and further suppressing peeling of the sealant layer, and a method for manufacturing the same.

Means for Solving the Problems

[0007] The pneumatic tire of the present invention for achieving the above object is a pneumatic tire including a tread portion extending in the tire circumferential direction and having 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 inner side in the tire radial direction of these sidewall portions. In the pneumatic tire, the tread portion includes a plurality of belt layers in which belt cords inclined with respect to the tire circumferential direction are embedded and the belt cords cross each other between the layers, and the plurality of belt layers include a first belt layer located on the innermost side in the tire radial direction and a second belt layer located outside the first belt layer. a sealant layer having a structure in which a strip material of the sealant is spirally disposed along the tire circumferential direction is formed on the inner surface of the tire in the tread portion, and the sealant is composed of a silicone-based composition. When the angle formed by the belt cord of the first belt layer and the belt cord of the second belt layer is 110° or less, the inclination direction of the belt material of the sealant with respect to the tire circumferential direction is the same as the inclination direction of the belt cord of the first belt layer with respect to the tire circumferential direction. When the angle formed by the belt cord of the first belt layer and the belt cord of the second belt layer exceeds 110°, the inclination direction of the belt material of the sealant with respect to the tire circumferential direction is opposite to the inclination direction of the belt cord of the first belt layer with respect to the tire circumferential direction.

[0008] The method for manufacturing a pneumatic tire of the present invention for achieving the above object is a method for manufacturing the above pneumatic tire, after manufacturing a pneumatic tire excluding the sealant layer, when forming the sealant layer by applying a sealant made of a silicone-based composition to the inner surface of the tire in the tread portion, the temperature of the sealant applied to the inner surface of the tire is made lower than 70°C.

Effect of the Invention

[0009] In the present invention, a sealant layer having a structure in which belt materials of the sealant are spirally arranged along the tire circumferential direction is formed on the inner surface of the tire in the tread portion. Since the sealant is composed of a silicone-based composition, the circumferential portions of the sealant belt materials are easily adapted to each other in the curing reaction process of the silicone-based composition, and the integrity between the circumferential portions of the sealant belt materials is improved. Therefore, the sealing performance of the sealant layer can be improved. Also, since the integrity between the circumferential portions of the sealant belt materials is good, it becomes difficult for the sealant layer to flow toward the center side in the tire width direction due to the centrifugal force generated during tire rotation, which also contributes to the improvement of the sealing performance. Furthermore, the sealant made of a silicone-based composition can be applied at a low temperature. For example, since the temperature of the sealant applied to the inner surface of the tire can be made lower than 70°C, there is also an advantage that the influence of heat on the tire can be reduced and the deterioration of tire performance can be avoided.

[0010] Further, when the angle formed by the belt cords of the first belt layer and the belt cords of the second belt layer is 110° or less, the inclination direction of the sealant strip material with respect to the tire circumferential direction is the same as the inclination direction of the belt cords of the first belt layer with respect to the tire circumferential direction, and when the angle formed by the belt cords of the first belt layer and the belt cords of the second belt layer exceeds 110°, the inclination direction of the sealant strip material with respect to the tire circumferential direction is opposite to the inclination direction of the belt cords of the first belt layer with respect to the tire circumferential direction. Therefore, the shearing force applied to the sealant layer due to the change in the angle of the belt cords during grounding can be reduced. Thereby, peeling of the sealant layer can be suppressed.

[0011] In the present invention, the silicone-based composition is preferably a two-component curable silicone. Since the two-component curable silicone has a low viscosity immediately after the two components are mixed, it can be applied even at low temperatures.

[0012] In the present invention, the glass transition temperature of the sealant preferably ranges from -120°C to -40°C. By using a sealant with a low glass transition temperature, it is possible to ensure good puncture sealing performance in a low-temperature environment.

[0013] In the present invention, the thickness of the sealant layer preferably ranges from 2.0 mm to 5.0 mm. Thereby, while ensuring puncture sealing performance, it is possible to suppress the deterioration of rolling resistance due to an increase in tire weight and to suppress the uneven distribution of the sealant layer caused by the flow of the sealant.

[0014] In the present invention, the width of the sealant layer is preferably 90% or more of the width of the first belt layer. In particular, it is preferable that the end portion of the sealant layer is disposed outside the end portion of the first belt layer in the tire width direction. By making the width of the sealant layer sufficiently large, it is possible to effectively prevent punctures in tubeless tires.

[0015] In the present invention, when a belt cover layer including an organic fiber cord 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 portion of the sealant layer is disposed outside the end portion of the belt cover layer in the tire width direction. By sufficiently increasing the width of the sealant layer, it is possible to effectively prevent a puncture of a pneumatic tire.

[0016] In the present invention, in all portions of the first belt layer, it is preferable that the distance L from the first belt layer to the sealant layer is 10 mm or less. Thereby, when a foreign object such as a nail penetrates the tread portion, the sealant easily flows into the belt layer, so that good puncture sealing performance can be ensured.

[0017] In the present invention, it is preferable that the ratio of the thickness S of the sealant layer to the distance L from the first belt layer to the sealant layer satisfies the relationship of S / L≧0.3. By making the thickness S of the sealant layer sufficiently large with respect to the distance L, good puncture sealing performance can be ensured.

[0018] In the present invention, it is preferable that a sound absorbing material is installed along the tire circumferential direction on the inner side in the tire radial direction of the sealant layer. In this case, since the sound absorbing material can be installed with respect to the sealant layer applied at a low temperature, damage to the sound absorbing material can be avoided and its sound absorbing effect can be maintained well.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0020] Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. FIGS. 1 to 4 show a pneumatic tire according to an embodiment of the present invention.

[0021] As shown in FIG. 1, the pneumatic tire of the present embodiment includes a tread portion 1 that extends in the tire circumferential direction and forms an annular 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 on the inner side in the tire radial direction of these sidewall portions 2.

[0022] 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 inner side to the outer side around a bead core 5 disposed in each bead portion 3. A bead filler 6 made of a rubber composition having a triangular cross-section is disposed on the outer periphery of the bead core 5.

[0023] On one side, 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 such that the belt cords cross each other between the layers. The plurality of belt layers 7 include a first belt layer 7A located at the innermost side in the tire radial direction and a second belt layer 7B located outside the first belt layer 7A, and the width of the first belt layer 7A is wider than the width of the second belt layer 7B. In the belt layer 7, the inclination angle of the belt cord with respect to the tire circumferential direction is set in the range of, for example, 10° to 70°. In particular, in the case of a passenger car tire, the inclination angle of the belt cord with respect to the tire circumferential direction is set in the range of, for example, 10° to 40°. As the belt cord of the belt layer 7, a steel cord is preferably used.

[0024] On the outer peripheral side of the belt layer 7, at least one belt cover layer 8 is arranged for the purpose of improving high-speed durability, in which reinforcing cords are arranged at an angle of, for example, 5° or less with respect to the tire circumferential direction. It is desirable that this belt cover layer 8 has a jointless structure in which a strip material formed by rubber-coating at least one reinforcing cord aligned is continuously wound at substantially 0° with respect to the tire circumferential direction. As the reinforcing cord of the belt cover layer 8, organic fiber cords such as nylon and polyethylene terephthalate (PET) are preferably used.

[0025] Note that the above-described tire internal structure shows a typical example in a pneumatic tire, but is not limited thereto. In the tread portion 1, various grooves including a plurality of main grooves 11 extending in the tire circumferential direction are formed.

[0026] In the pneumatic tire described above, a sealant layer 20 is formed on the inner surface 10 of the tread portion 1 so as to be continuous in the tire circumferential direction. It is preferable that the center position of the sealant layer 20 in the tire width direction coincides with the tire equator, but the center position may be shifted toward either one side in the tire width direction from the tire equator. The distance in the tire width direction between the center position of the sealant layer 20 and the tire equator is preferably 10 mm or less, more preferably 5 mm or less. Thereby, the sealant layer 20 does not adversely affect the tire balance. As shown in FIG. 3 or FIG. 4, the sealant layer 20 has a structure in which a sealant strip 21 is arranged in a spiral shape along the tire circumferential direction. The sealant of the sealant layer 20 is composed of a silicone-based composition. The silicone-based composition includes a synthetic polymer compound having a main skeleton formed by siloxane bonds.

[0027] In the pneumatic tire described above, when the angle θ formed by the belt cord of the first belt layer 7A and the belt cord of the second belt layer 7B is 110° or less, as shown in FIG. 3, the inclination direction of the sealant strip 21 with respect to the tire circumferential direction is set in the same direction as the inclination direction of the belt cord of the first belt layer 7A with respect to the tire circumferential direction. Further, when the angle θ formed by the belt cord of the first belt layer 7A and the belt cord of the second belt layer 7B is more than 110°, as shown in FIG. 4, the inclination direction of the sealant strip 21 with respect to the tire circumferential direction is set in the direction opposite to the inclination direction of the belt cord of the first belt layer 7A with respect to the tire circumferential direction. That is, according to the findings of the present inventor, when the angle θ is 110° or less, an angle change occurs such that the cord angle of the first belt layer 7A becomes smaller during grounding, while when the angle θ is more than 110°, an angle change occurs such that the cord angle of the first belt layer 7A becomes larger during grounding. Therefore, by optimizing the inclination direction of the sealant strip 21 with respect to the tire circumferential direction according to the assumed angle change during grounding, the shearing force applied to the sealant layer 20 during grounding can be reduced. Thereby, peeling of the sealant layer 20 can be suppressed.

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

[0029] FIG. 5 shows a specific manufacturing method of the pneumatic tire of FIG. 1, and FIG. 6 shows the sealant layer formed on the inner surface of the tire in the tread portion. In FIG. 5, the sealant extruding device 31 is configured to mix the sealant supplied from the pumps 32 and 33 and continuously discharge the mixed sealant as a strip material 21 from the nozzle 34. This sealant extruding device 31 is configured such that the position of the nozzle 34 is displaceable. Therefore, by moving the nozzle 34 in the tire axial direction while rotating the tire from a state where the nozzle 34 is close to the inner surface 10 of the tire, the strip material 21 of the sealant can be spirally arranged on the inner surface 10 of the tire while being inclined with respect to the tire circumferential direction Tc (see FIG. 6). The circumferential portions of the strip material 21 of the sealant arranged in a spiral shape are in close contact with each other. The strip material 21 of the sealant arranged in this spiral shape is 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 on the tire inner surface 10 in the tread portion 1 is formed. Since the sealant is composed of a silicone-based composition, the circumferential portions of the sealant strip 21 are more likely to fit together in the curing reaction process of the silicone-based composition, and the integrity between the circumferential portions of the sealant strip 21 is improved. Therefore, the sealing performance of the sealant layer 20 can be improved. Further, since the integrity between the circumferential portions of the sealant strip 21 is good, it becomes difficult for the sealant layer 20 to flow toward the center side in the tire width direction due to the centrifugal force generated during tire rotation, and this also contributes to the improvement of the sealing performance. Furthermore, when a silicone-based composition is used as the sealant of the sealant layer 20, it has the advantages of excellent weather resistance and low temperature dependence of physical properties.

[0031] 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 lower than 70°C. Thereby, the influence of heat on the tire can be reduced, and the deterioration of tire performance can be avoided. When this temperature is 70°C or higher, the influence of heat on the tire becomes large, which becomes a factor in deteriorating tire performance. In particular, it is desirable that the temperature of the sealant applied to the tire inner surface 10 is 35°C or lower. Also, from the viewpoint of the fluidity of the silicone-based composition, the lower limit value of the temperature of the sealant applied to the tire inner surface 10 is preferably 20°C.

[0032] As the silicone-based composition constituting the sealant of the sealant layer 20, one-component curable silicone or two-component curable silicone can be used, but it is particularly preferable to use two-component curable silicone. Examples of the one-component curable silicone include moisture-curable silicone. The two-component curable silicone is composed of a first liquid and a second liquid. By mixing these first liquid and second liquid, the curing reaction starts, and the stability as the sealant layer 20 is ensured after curing. In the above-described apparatus, the first liquid and the second liquid of the two-component curable silicone are respectively supplied from pumps 32 and 33. Since the two-component curable silicone has a low viscosity immediately after the two liquids are mixed, it can be applied even at a low temperature. In particular, it is preferable that the two-component curable silicone has a period of up to complete curing of 5 days or more.

[0033] The two-component curable silicone is composed of, for example, a condensation-curable silyl-terminated polymer, a silane crosslinking agent, a condensation catalyst, a filler, etc. Examples of the condensation-curable silyl-terminated polymer include polydialkylsiloxane, alkylphenylsiloxane, an organic polymer having a silyl group (for example, silyl polyether, silyl acrylate), polyisobutylene having a silyl group, etc. Examples of the silane crosslinking agent include alkoxy-functional silane, oximosilane, acetoxysilane, enoxysilane, etc. Examples of the filler include iron oxide, titanium dioxide, carbon black, talc, etc. Examples of the condensation catalyst include titanate, zirconate, etc. These condensation-curable silyl-terminated polymer, silane crosslinking agent, condensation catalyst, and filler are stored in a state divided into the first liquid and the second liquid in a combination in which the curing reaction does not proceed, and are mixed at the time of use. Examples of the two-component curable silicone include those described in Japanese Patent Application Laid-Open No. 2018-503725 and Japanese Patent Application Laid-Open No. 2022-550962. As a commercially available product of the two-component curable silicone, for example, SST-2650 manufactured by Dow can be used.

[0034] In the pneumatic tire described above, it is preferable that the glass transition temperature of the sealant in the sealant layer 20 is in the range of -120°C to -40°C. By using a sealant with a low glass transition temperature, it is possible to ensure good puncture sealing performance in a low-temperature environment. If the glass transition temperature of the sealant is higher than -40°C, the puncture sealing performance in a low-temperature environment will deteriorate.

[0035] In the pneumatic tire described above, as shown in FIG. 2, it is preferable that the thickness S of the sealant layer 20 is in the range of 2.0 mm to 5.0 mm. Thereby, while ensuring puncture sealing performance, it is possible to suppress the deterioration of rolling resistance due to an increase in tire weight, and to suppress the uneven distribution of the sealant layer 20 caused by the flow of the sealant. Here, if the thickness S of the sealant layer 20 is less than 2.0 mm, the puncture sealing performance will deteriorate. Conversely, if it is greater than 5.0 mm, the rolling resistance will deteriorate due to an increase in tire weight, and there is a risk of uneven distribution of the sealant layer 20 due to the flow of the sealant. 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, for example, by photographing the tire meridian cross-section at 8 locations on the tire circumference using a CT scan, and measuring the thickness of the sealant layer 20 at 5 points in each of the photographed images, 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 positions, and then calculating from the measured values at a total of 40 points.

[0036] In the pneumatic tire described above, as shown in FIG. 1, it is preferable that the width Ws of the sealant layer 20 is 90% or more of the width Wb of the first belt layer 7A located at the innermost side in the tire radial direction. In particular, it is preferable that the end portion of the sealant layer 20 is disposed outside the tire width direction from the end portion of the first belt layer 7A located at the innermost side 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, it is possible to effectively prevent the pneumatic tire from being punctured. Here, if the width Ws of the sealant layer 20 is less than 90% of the width Wb of the first belt layer 7A, the puncture sealing performance will deteriorate.

[0037] For the same reason, when a belt cover layer 8 including an organic fiber cord 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 end portion of the sealant layer 20 is disposed outside the end portion of the belt cover layer 8 in the tire width direction. By making the width of the sealant layer 20 sufficiently large, it is possible to effectively prevent a puncture of the pneumatic tire.

[0038] In the above pneumatic tire, as shown in FIG. 2, at all locations of the first belt layer 7A located at the innermost side in the tire radial direction, it is preferable that the distance (shortest distance) L from the first belt layer 7A to the sealant layer 20 is 10 mm or less. Thereby, when a foreign object such as a nail penetrates the tread portion 1, the sealant easily flows to the first belt layer 7A, so that good puncture sealing performance can be ensured. If there is a portion where the distance L from the first belt layer 7A to the sealant layer 20 is greater than 10 mm, the puncture sealing performance in that portion may become insufficient.

[0039] 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 first belt layer 7A located at the innermost side in the tire radial direction to the sealant layer 20 satisfies the relationship of S / L≧0.3. By making the thickness S of the sealant layer 20 sufficiently large with respect to the distance L, good puncture sealing performance can be ensured. If the ratio S / L is less than 0.3, the puncture sealing performance deteriorates.

[0040] FIG. 7 shows a pneumatic tire according to another embodiment of the present invention. In FIG. 7, a sound absorbing material 40 is installed along the tire circumferential direction on the inner side in the tire radial direction of the sealant layer 20. The sound absorbing material 40 is composed of a porous material having continuous bubbles and has predetermined sound absorbing characteristics based on the 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 adhered onto the sealant layer 20 based on the adhesiveness of the sealant layer 20 after the formation of the sealant layer 20. In this case, since the sound absorbing material 40 is installed with respect to the sealant layer 20 applied at a low temperature, damage to the sound absorbing material 40 can be avoided and its sound absorbing effect can be maintained well.

Example

[0041] 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 on the inner surface of the tire in the tread portion is formed. Tires of Comparative Examples 1 to 2 and Examples 1 to 5 were manufactured with various differences in the constituent material of the sealant layer, the thickness S of the sealant layer, the ratio of the width of the sealant layer to the width of the belt layer, the inclination direction of the sealant strip, the distance L from the belt layer located at the innermost side in the tire radial direction to the sealant layer, and S / L as shown in Table 1. Also, a tire of Conventional Example 1 having no sealant layer on the inner surface of the tire in the tread portion was prepared. The angle θ (belt cord crossing angle) formed by the belt cord of the first belt layer and the belt cord of the second belt layer is as shown in Table 1.

[0042] Regarding the inclination direction of the sealant strip, the case where the inclination direction of the sealant strip with respect to the tire circumferential direction is in the same phase as the inclination direction of the belt cord of the belt layer located at the innermost side in the tire radial direction is indicated by "same", and the case where 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 is indicated by "reverse".

[0043] For these test tires, the rolling resistance, peelability, and puncture sealing property were evaluated by the following test methods, and the results are shown together in Table 1.

[0044] Rolling resistance: Each test tire was assembled on a wheel with a rim size of 19×8.5J and mounted on a rolling resistance tester. With the air pressure set at 210 kPa, the rolling resistance was measured in accordance with JIS-D4234. The evaluation results were shown as an index with the reciprocal of the measured value, with Conventional Example 1 taken as 100. The larger this index value, the smaller the rolling resistance.

[0045] Peelability: Each test tire was assembled onto a wheel with a rim size of 19×8.5J and mounted on an indoor drum tester (drum diameter 1707 mm). After driving for 6000 km under the conditions of controlling the ambient temperature at 38±3°C, setting the air pressure at 120 kPa, setting the load at 120% of the maximum load capacity, and setting the speed at 80 km / h, the sealant layer on the inner surface of the tire was observed. The evaluation results were indicated as "◎" when there was no lifting or displacement in the sealant layer, "○" when there was no lifting in the sealant layer and the displacement was less than 5 cm, and "×" when there was lifting in the sealant layer or the displacement was 5 cm or more.

[0046] Puncture sealing performance: Each test tire was assembled onto a wheel with a rim size of 19×8.5J, the initial air pressure was set at 250 kPa, a nail with a diameter of 4.0 mm was driven into the tread part, and after leaving the tire for 1 hour with the nail pulled out, the air pressure was measured again, and the pressure drop rate relative to the initial air pressure was determined. The evaluation results were indicated as "◎" 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%.

[0047]

Table 1

[0048] As can be seen from Table 1, the tires of Examples 1 to 5 all had good puncture sealing performance. In contrast, for the tire of Comparative Example 1, since a sealant mainly composed of butyl rubber was used to form a sealant layer having a structure in which the belt material of the sealant was arranged spirally along the tire circumferential direction, the integrality between the circumferential portions of the sealant belt material was not good. As a result, the sealing performance by the sealant layer was insufficient. In the tire of Comparative Example 2, when the angle θ formed by the belt cord of the first belt layer and the belt cord of the second belt layer was 110° or less, since the inclination direction of the belt material of the sealant with respect to the tire circumferential direction was opposite to the inclination direction of the belt cord of the first belt layer with respect to the tire circumferential direction, the peelability of the sealant layer was slightly reduced compared to Examples 1 to 5.

[0049] Next, in a pneumatic tire having a tread portion, a pair of sidewall portions, and a pair of bead portions with a tire size of 255 / 45R19, a sealant layer having a structure in which the belt material of the sealant was arranged spirally along the tire circumferential direction was formed on the inner surface of the tire in the tread portion. Tires of Comparative Examples 11 to 12 and Examples 11 to 15 were manufactured with various differences in the constituent material of the sealant layer, the thickness S of the sealant layer, the ratio of the width of the sealant layer to the width of the belt layer, the inclination direction of the belt material of the sealant, the distance L from the belt layer located at the innermost side in the tire radial direction to the sealant layer, and S / L as shown in Table 2. Also, a tire of Conventional Example 11 without a sealant layer on the inner surface of the tire in the tread portion was prepared. The angle θ (the intersection angle of the belt cords) formed by the belt cord of the first belt layer and the belt cord of the second belt layer is as shown in Table 2.

[0050] For these test tires, the rolling resistance, peelability, and puncture sealing performance were evaluated by the above-described test method, and the results are shown together in Table 2. However, the evaluation criteria for the rolling resistance were based on Conventional Example 11.

[0051]

Table 2

[0052] As can be seen from Table 2, all of the tires of Examples 11 to 15 had good puncture sealing performance. On the other hand, in the tire of Comparative Example 11, when forming a sealant layer having a structure in which the belt material of the sealant is arranged spirally along the tire circumferential direction, a sealant mainly composed of butyl rubber is used. Therefore, the integrality between the circumferential portions of the sealant belt material is not good, and as a result, the sealing performance by the sealant layer was insufficient. In the tire of Comparative Example 12, when the angle θ formed by the belt cord of the first belt layer and the belt cord of the second belt layer exceeds 110°, since the inclination direction of the belt material of the sealant with respect to the tire circumferential direction is the same as the inclination direction of the belt cord of the first belt layer with respect to the tire circumferential direction, the peelability of the sealant layer was slightly lower than that of Examples 11 to 15.

Explanation of Signs

[0053] 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 10 Tire inner surface 20 Sealant layer 21 Belt material of sealant 40 Sound-absorbing material

Claims

1. In a pneumatic tire comprising a tread portion extending in the tire circumferential direction to form an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on the inner side in the tire radial direction of these sidewall portions, a plurality of belt layers including belt cords inclined with respect to the tire circumferential direction and arranged such that the belt cords cross each other between layers are embedded in the tread portion, and the plurality of belt layers include a first belt layer located at the innermost side in the tire radial direction and a second belt layer located outside the first belt layer, a sealant layer having a structure in which a strip material of the sealant is spirally arranged along the tire circumferential direction on the inner surface of the tire in the tread portion, and the sealant is composed of a silicone-based composition, when the angle formed by the belt cord of the first belt layer and the belt cord of the second belt layer is 110° or less, the inclination direction of the strip material of the sealant with respect to the tire circumferential direction is the same as the inclination direction of the belt cord of the first belt layer with respect to the tire circumferential direction, and when the angle formed by the belt cord of the first belt layer and the belt cord of the second belt layer exceeds 110°, the inclination direction of the strip material of the sealant with respect to the tire circumferential direction is opposite to the inclination direction of the belt cord of the first belt layer with respect to the tire circumferential direction. A pneumatic tire characterized by this.

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

3. The pneumatic tire according to claim 1 or 2, wherein the glass transition temperature of the sealant is in the range of -120°C to -40°C.

4. The pneumatic tire according to claim 1 or 2, wherein the thickness of the sealant layer is in the range of 2.0 mm to 5.0 mm.

5. The pneumatic tire according to claim 1 or 2, wherein the width of the sealant layer is 90% or more of the width of the first belt layer.

6. The pneumatic tire according to claim 5, wherein the end portion of the sealant layer is disposed outside the end portion of the first belt layer in the tire width direction.

7. A pneumatic tire according to claim 6, wherein a belt cover layer including an organic fiber cord oriented in the tire circumferential direction is embedded in the tread portion on the outer peripheral side of the belt layer, and an end portion of the sealant layer is disposed outside the end portion of the belt cover layer in the tire width direction.

8. The pneumatic tire according to claim 1 or 2, wherein in all portions of the first belt layer, a distance L from the first belt layer to the sealant layer is 10 mm or less.

9. The pneumatic tire according to claim 8, wherein a ratio of a thickness S of the sealant layer to a distance L from the first belt layer to the sealant layer satisfies a relationship of S / L ≧ 0.

3.

10. The pneumatic tire according to claim 1 or 2, wherein a sound-absorbing material is installed along the tire circumferential direction on the inner side in the tire radial direction of the sealant layer.

11. A method for manufacturing a pneumatic tire according to claim 1 or 2, after manufacturing a pneumatic tire excluding the sealant layer, when forming the sealant layer by applying a sealant made of a silicone-based composition to the inner surface of the tire in the tread portion, the temperature of the sealant applied to the inner surface of the tire is made lower than 70°C.

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

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