Pneumatic tire

Abstract

To provide a pneumatic tire capable of improving adhesiveness to a tire inner surface of a sealant layer.SOLUTION: There is provided a pneumatic tire which comprises a tread part 1 extending in the tire circumferential direction to form 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 the inner side of these sidewall parts 2 in the tire radial direction, in which a bladder transfer pattern including a plurality of projection strips 9g extending in the tire width direction is formed on a tire inner surface 10 and a release agent is applied to the tire inner surface 10, wherein a sealant layer 20 having a structure in which a band material 21 of a sealant is spirally disposed along the tire circumferential direction is formed on the tire inner surface 10 in the tread part 1, the sealant is composed of a silicone-based composition and the width L1 of the band material 21 satisfies the relationship L1≤L2 relative to the intervals L2 in the tire width direction of the projection strips 9g.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a pneumatic tire having a sealant layer on the inner surface of the tire in the tread portion, and more particularly to a pneumatic tire that makes it possible to improve the adhesion of the sealant layer to the inner surface of the tire. [Background technology]

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

[0003] Conventionally, sealants constituting a sealant layer have generally been rubber compositions mainly composed of butyl rubber (see, for example, Patent Documents 1 to 3). Examples of butyl rubber include butyl rubber (IIR) and halogenated butyl rubbers such as brominated butyl rubber (Br-IIR) and chlorinated butyl rubber (Cl-IIR). Such sealants are applied to the inner surface of a tire in a softened state by heating to a high temperature (see, for example, Patent Document 4). More specifically, a strip of sealant that has been softened by heating to a high temperature is spirally arranged on the inner surface of the tire in the circumferential direction of the tire to form a sealant layer.

[0004] However, if peeling occurs at the edge of the sealant strip, the peeling of the sealant layer can spread from that point, which can lead to a decrease in sealing ability in the event of a puncture. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6583456 [Patent Document 2] Patent No. 6620851 [Patent Document 3] Patent No. 7319533 [Patent Document 4] Patent No. 6124967 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a pneumatic tire that enables improved adhesion of a sealant layer to the inner surface of the tire. [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 tire circumferential direction to form an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on the tire radially inward side of the sidewall portions, and a bladder transfer pattern including a plurality of protrusions extending in the tire width direction is formed on the tire inner surface, and a release agent is applied to the tire inner surface. The tire is characterized in that a sealant layer having a structure in which a strip of sealant is spirally arranged along the tire circumferential direction is formed on the inner surface of the tire in the tread portion, the sealant is made of a silicone-based composition, and a width L1 of the strip and a spacing L2 of the ridges in the tire width direction satisfy the relationship L1≦L2. [Effects of the Invention]

[0008] As a result of extensive research into the adhesion of a sealant layer to the inner surface of a tire, the inventors discovered that if the end of the sealant strip is positioned so as to overlap with a protrusion included in a bladder transfer pattern, the end of the sealant strip is likely to peel off when driving on rough roads, etc., and this led to the present invention.

[0009] Specifically, in the present invention, a pneumatic tire having a bladder transfer pattern formed on its inner surface, the pattern includes a plurality of ridges extending in the tire width direction. A sealant layer is formed on the tire inner surface in the tread portion, the sealant layer having a structure in which a sealant strip is spirally arranged along the tire circumferential direction. The width L1 of the strip satisfies the relationship L1≦L2 relative to the spacing L2 between the ridges in the tire width direction, thereby reducing the frequency with which the ends of the sealant strip overlap with the ridges included in the bladder transfer pattern. This reduces peeling originating from both ends of the strip and improves the adhesion of the sealant layer to the tire inner surface. Furthermore, in pneumatic tires in which a release agent is applied to the tire inner surface, the release agent typically contains a silicone-based composition, which impairs the adhesion of a sealant layer composed of a rubber composition primarily containing butyl rubber to the tire inner surface. In contrast, a sealant layer containing a sealant composed of a silicone-based composition has good compatibility with the release agent, resulting in good adhesion to the tire inner surface coated with the release agent.

[0010] When the sealant is composed of a rubber composition primarily containing butyl rubber, the sealant cools before the circumferential portions of the sealant strip blend together, resulting in poor integration between the circumferential portions of the sealant strip, resulting in insufficient sealing by the sealant layer. Furthermore, when the circumferential portions of the sealant strip are poorly integrated, the sealant layer is more likely to flow toward the center of the tread due to the centrifugal force generated during tire rotation, which also contributes to reduced sealing. In contrast, when the sealant is composed of a silicone-based composition, the circumferential portions of the sealant strip blend together more easily during the curing reaction process of the silicone-based composition, improving the integration between the circumferential portions of the sealant strip, thereby improving the sealing by the sealant layer. Furthermore, because the circumferential portions of the sealant strip are well integrated, the sealant layer 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 improved sealing. Furthermore, sealants made from silicone-based compositions can be applied at low temperatures; for example, the temperature of the sealant applied to the inner surface of a tire can be lowered to below 70°C, which has the advantage of reducing the effects of heat on the tire and preventing deterioration of tire performance.

[0011] In the present invention, it is preferable that the width L1 of the strip material and the spacing L2 of the ridges in the tire width direction satisfy the relationship 0.2≦L1 / L2≦0.7. This makes it possible to obtain an improved adhesiveness of the sealant layer without deteriorating tire productivity or ride comfort. In particular, it is preferable that both ends of the strip material are positioned so as not to overlap with the ridges. This makes it possible to obtain the maximum improved adhesiveness of the sealant layer.

[0012] In the present invention, in a pneumatic tire in which a convex portion caused by a splice of tire constituent members is formed on the tire inner surface, it is preferable that both end portions of the strip material are arranged in positions that do not overlap the convex portion. If the end portion of the sealant strip material is arranged in a position that overlaps the convex portion caused by the splice of tire constituent members, the end portion of the sealant strip material is likely to peel off, but by arranging both end portions of the strip material in positions that do not overlap the convex portion, peeling starting from both end portions of the strip material can be suppressed and the adhesion of the sealant layer to the tire inner surface can be improved.

[0013] Both ends of the strip are preferably positioned at least 5 mm away from any protrusions due to splices, which effectively improves the adhesion of the sealant layer.

[0014] The tire component is preferably an inner liner layer. Since a convex portion caused by a splice of the inner liner layer significantly affects the adhesiveness of the sealant layer, the adhesiveness of the sealant layer can be effectively improved by separating both ends of the strip material from the convex portion caused by the splice of the inner liner layer.

[0015] In the present invention, the sealant preferably has a storage modulus G' of 20 kPa or less at 100° C. When the sealant has a small storage modulus G' at 100° C., vibration of the sealant layer is suppressed, improving ride comfort.

[0016] In the present invention, it is preferable that the loss modulus G" of the sealant at 100°C is 5 kPa or less. When the loss modulus G" of the sealant at 100°C is small, heat generation in the sealant layer is suppressed, thereby reducing the impact on durability.

[0017] 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 properties.

[0018] In the present invention, the silicone composition is preferably a two-component curing silicone, which has low viscosity immediately after mixing the two components, making it possible to apply the composition even at low temperatures.

[0019] In the present invention, the storage modulus G' and loss modulus G" of the sealant are measured in accordance with JIS-K6394 using a viscoelasticity spectrometer (manufactured by Toyo Seiki Seisakusho, Ltd.) under conditions of a frequency of 20 Hz, an initial strain of 10%, a dynamic strain of ±2%, and a temperature of 100°C. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a meridian cross-sectional view showing a pneumatic tire according to an embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing a tread portion of the pneumatic tire of FIG. [Figure 3] 2 is a cross-sectional view illustrating a method for manufacturing the pneumatic tire of FIG. 1. [Figure 4] 2 is a plan view showing a sealant layer formed on the inner surface of the tire in the tread portion of the pneumatic tire of FIG. 1. FIG. [Figure 5] 2 is a plan view showing an inner liner layer and a strip of sealant of the pneumatic tire of FIG. 1. FIG. [Figure 6] 10 is a cross-sectional view showing the state in which the end of the sealant strip does not overlap the protrusion resulting from the splice of the inner liner layer. FIG. [Figure 7] 10 is a cross-sectional view showing an end of a sealant strip overlapping a protrusion resulting from a splice in an inner liner layer. FIG. [Figure 8] FIG. 10 is a meridian cross-sectional view showing a pneumatic tire according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the accompanying drawings, in which: Figures 1 and 2 show a pneumatic tire according to an embodiment of the present invention.

[0022] As shown in FIG. 1, the pneumatic tire of this embodiment includes a tread portion 1 extending circumferentially in a ring shape, a pair of sidewall portions 2, 2 arranged on both sides of the tread portion 1, and a pair of bead portions 3, 3 arranged radially inward of the sidewall portions 2.

[0023] A carcass layer 4 is mounted between a pair of bead portions 3, 3. This carcass layer 4 includes a plurality of carcass cords extending in the tire radial direction, and is folded back from the inside to the outside of the tire around a bead core 5 disposed in each bead portion 3. A bead filler 6 made of a rubber composition and having a triangular cross section is disposed on the outer periphery of the bead core 5.

[0024] On the other hand, multiple belt layers 7 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. These belt layers 7 include multiple belt cords that are inclined with respect to the tire circumferential direction, and are arranged so that the belt cords cross each other between the layers. The multiple belt layers 7 include a first belt layer 7A located on the innermost side in the tire radial direction and a second belt layer 7B located on the outer side of 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 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.

[0025] At least one belt cover layer 8 is arranged on the outer periphery of the belt layer 7, with the aim of improving high-speed durability, and is made up of reinforcing cords arranged at an angle of, for example, 5° or less relative to the tire circumferential direction. This belt cover layer 8 preferably has a jointless structure in which a strip material made of at least one reinforcing cord that has been aligned and rubber-coated is continuously wound at an angle of substantially 0° relative to the tire circumferential direction. The reinforcing cord of the belt cover layer 8 is preferably an organic fiber cord such as nylon or polyethylene terephthalate (PET).

[0026] The tire internal structure described above 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, and the inner surface of the inner liner layer 9 forms the tire inner surface 10. Various grooves, including multiple main grooves 11 extending in the tire circumferential direction, are formed in the tread portion 1. In addition, to ensure mold releasability during tire vulcanization, a mold release agent containing a silicone-based composition is applied to the tire inner surface 10.

[0027] In the pneumatic tire described above, 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 CL, but the center position may be offset from the tire equator CL 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 CL 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 layer 20 has a structure in which a sealant strip 21 is spirally arranged along the tire circumferential direction (see FIG. 4). 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.

[0028] The above-described 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 in which the belt layer 7 and belt cover layer 8 are 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 the sealant layer 20.

[0029] FIG. 3 shows a specific manufacturing method for the pneumatic tire of FIG. 1, and FIG. 4 shows a sealant layer formed on the tire inner surface in the tread portion. In FIG. 3, a sealant extrusion device 31 mixes sealants supplied from pumps 32 and 33 and continuously discharges the mixed sealant as a strip 21 from a nozzle 34. The sealant extrusion device 31 is configured so that the position of the nozzle 34 can be freely changed. Therefore, by moving the nozzle 34 in the axial direction of the tire while rotating the tire from a state in which the nozzle 34 is close to the tire inner surface 10, the sealant strip 21 can be arranged spirally on the tire inner surface 10 while being inclined with respect to the tire circumferential direction Tc (see FIG. 4). 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] FIG. 5 shows the inner liner layer and sealant strip of the pneumatic tire of FIG. 1. In the pneumatic tire, as shown in FIG. 5, a bladder transfer pattern including multiple ridges 9g extending in the tire width direction Tw is formed on the tire inner surface 10. The protrusions 9g protrude from the tire inner surface 10 typically in the range of 0.2 mm to 0.4 mm. Furthermore, the spacing L2 between the ridges 9g in the tire width direction Tw typically in the range of 5.0 mm to 15.0 mm. During tire vulcanization, the tire inner surface 10 is pressed by a rubber bladder, and the outer surface of the bladder has multiple fine grooves formed in a stripe pattern to prevent air pockets. Therefore, a bladder transfer pattern including multiple ridges 9g is formed on the tire inner surface 10. These ridges 9g affect the adhesion of the sealant layer 20.

[0031] Therefore, width L1 of sealant strip 21 is set so as to satisfy the relationship L1≦L2 with respect to the spacing L2 of protrusions 9g in the tire width direction Tw. If ends E1, E2 of sealant strip 21 are positioned so as to overlap with protrusions 9g included in the bladder transfer pattern, ends E1, E2 of strip 21 are likely to peel off, but by setting width L1 of strip 21 to be equal to or less than spacing L2 of protrusions 9g in the tire width direction Tw, it is possible to reduce the frequency with which ends E1, E2 of sealant strip 21 overlap with protrusions 9g included in the bladder transfer pattern. For example, if the width L1 of the strip 21 is greater than the spacing L2 of the protrusions 9g in the tire width direction Tw, each end E1, E2 of the strip 21 will be positioned to straddle multiple protrusions 9g. However, if the width L1 of the strip 21 is equal to or less than the spacing L2 of the protrusions 9g in the tire width direction Tw, each end E1, E2 of the strip 21 will overlap only one protrusion 9 or will not overlap any protrusions 9 at all. As a result, the adhesion of the sealant layer 20 can be improved. The both end portions E1, E2 of the strip 21 refer to the portions extending from both ends of the strip 21 up to 5 mm in the longitudinal direction of the strip 21.

[0032] In the pneumatic tire described above, when a bladder transfer pattern including multiple ridges 9g extending in the tire width direction is formed on the tire inner surface 10, 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, and the width L1 of the strip 21 satisfies the relationship L1≦L2 relative to the spacing L2 of the ridges 9g in the tire width direction, thereby reducing the frequency with which the ends E1, E2 of the sealant strip 21 overlap with the ridges 9g included in the bladder transfer pattern. This suppresses peeling originating from both ends E1, E2 of the strip 21 and improves the adhesion of the sealant layer 20 to the tire inner surface 10. Furthermore, in a pneumatic tire in which a release agent is applied to the tire inner surface 10, the sealant layer 20 containing a sealant made of a silicone-based composition has good compatibility with the release agent, and therefore good adhesion to the tire inner surface 10 to which the release agent is applied.

[0033] Furthermore, in the above-described pneumatic tire, 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 of the tread portion 1. Since the sealant is composed of a silicone-based composition, the circumferential portions of the sealant strip 21 are easily fitted together during the curing reaction process of the silicone-based composition, improving the unity of the circumferential portions of the sealant strip 21, thereby improving the sealing performance of the sealant layer 20. Furthermore, because the circumferential portions of the sealant strip 21 are well-integrated, the sealant layer 20 is less likely to flow toward the center of the tire width direction due to centrifugal force generated during tire rotation, which also contributes to improved sealing performance. Furthermore, when a silicone-based composition is used as the sealant for the sealant layer 20, it has the advantages of excellent weather resistance and low temperature dependency of physical properties.

[0034] Because silicone-based compositions have good fluidity even at low temperatures, it is preferable to set the temperature of the sealant applied to the tire inner surface 10 to below 70°C. This reduces the thermal impact on the tire and prevents deterioration of tire performance. If this temperature is 70°C or higher, the thermal impact on the tire will be greater, which will cause deterioration of tire performance. In particular, it is desirable for the temperature of the sealant applied to the tire inner surface 10 to be 35°C or lower. Furthermore, from the viewpoint of the fluidity of the silicone-based composition, it is preferable for the lower limit of the temperature of the sealant applied to the tire inner surface 10 to be 20°C.

[0035] In the pneumatic tire, the width L1 of the strip 21 and the spacing L2 of the ridges 9g in the tire width direction Tw preferably satisfy the relationship 0.2≦L1 / L2≦0.7. This improves the adhesiveness of the sealant layer 20 without compromising tire productivity or ride comfort. If the L1 / L2 ratio is less than 0.2, the sealant application time increases and the strip 21 becomes more susceptible to tearing, reducing tire productivity. Conversely, if the L1 / L2 ratio is greater than 0.7, tire balance is affected, resulting in a worsening of ride comfort. In particular, it is preferable that both end portions E1 and E2 of the strip 21 are positioned so as not to overlap the ridges 9g. This maximizes the adhesiveness improvement of the sealant layer 20.

[0036] In the pneumatic tire, the inner liner layer 9, which is one of the tire constituent members, is formed by joining sheet materials together in an annular shape along the tire circumferential direction, and both ends of the sheet materials in the tire circumferential direction Tc are spliced ​​together to form a convex portion 9s on the tire inner surface 10 resulting from the splice and extending in the tire width direction Tw (see FIG. 4). The protruding height of the convex portion 9s from the tire inner surface 10 is 0.2 mm or more, generally in the range of 0.2 mm to 0.5 mm. In addition to the inner liner layer 9, the carcass layer 4 can also be used as a tire constituent member to be spliced.

[0037] When forming a sealant layer 20 by spirally applying a sealant strip 21 to the tire inner surface 10 in the tread portion 1 along the tire circumferential direction, it is preferable that, as shown in Figure 4, both the end E1 on the application start side of the sealant strip 21 and the end E2 on the application end side are positioned so as not to overlap with the convex portion 9s caused by the splice of the inner liner layer 9 (tire constituent member).

[0038] Fig. 6 shows a state in which the end of the sealant strip does not overlap the convex portion caused by the splice of the inner liner layer, while Fig. 7 shows a state in which the end of the sealant strip overlaps the convex portion caused by the splice of the inner liner layer. As shown in Fig. 7, if ends E1 and E2 of sealant strip 21 overlap convex portion 9s caused by the splice of inner liner layer 9, a portion of strip 21 will not contact tire inner surface 10, making peeling more likely to occur. In contrast, as shown in Fig. 6, by not overlapping ends E1 and E2 of sealant strip 21 with convex portion 9s caused by the splice of inner liner layer 9, peeling of strip 21 can be suppressed.

[0039] In the above-described pneumatic tire, when a convex portion 9s caused by a splice of the inner liner layer 9 (tire constituent member) is formed on the tire inner surface 10, a sealant layer 20 having a structure in which a strip of sealant 21 is arranged spirally along the tire circumferential direction is formed on the tire inner surface 10 in the tread portion 1, and both end portions E1, E2 of the strip 21 are arranged in positions that do not overlap with the convex portion 9s, thereby suppressing peeling starting from both end portions E1, E2 of the strip 21 and improving the adhesion of the sealant layer 20 to the tire inner surface 10.

[0040] In the above pneumatic tire, both end portions E1, E2 of the strip material 21 are preferably positioned at a distance of 5 mm or more from the protruding portion 9s. That is, as shown in FIG. 4, the distance D from the protruding portion 9s to each of the end portions E1, E2 of the strip material 21 is preferably 5 mm or more. By sufficiently separating the end portions E1, E2 of the strip material 21 from the protruding portion 9s caused by the splice, the adhesiveness of the sealant layer 20 can be effectively improved. If the distance D is less than 5 mm, the adhesiveness improvement effect is reduced. In particular, it is desirable that the distance D from the protruding portion 9s to each of the end portions E1, E2 of the strip material 21 be 10 mm or more.

[0041] In the above pneumatic tire, the tire component in which the convex portions 9s caused by the splice are taken into consideration is preferably the inner liner layer 9. The convex portions 9s caused by the splice of the inner liner layer 9 significantly affect the adhesiveness of the sealant layer 20, and therefore, by separating both ends E1, E2 of the strip material 21 from the convex portions 9s caused by the splice of the inner liner layer 9, the adhesiveness of the sealant layer 20 can be effectively improved.

[0042] The silicone-based composition constituting the sealant of the sealant layer 20 can be a one-component curing silicone or a two-component curing silicone, with two-component curing silicone being particularly preferred. Examples of one-component curing silicones include moisture-curing silicone. Two-component curing silicones are composed of a first component and a second component, and mixing these components initiates a curing reaction, ensuring the stability of the sealant layer 20 after curing. In the above-described device, the first component and the second component of the two-component curing silicone are supplied from pumps 32 and 33, respectively. Two-component curing silicones have low viscosity immediately after mixing, allowing them to be applied even at low temperatures. In particular, two-component curing silicones that take 5 days or more to fully cure are preferred.

[0043] Two-component curing silicones are composed of, for example, a condensation-curable silyl-terminated polymer, a silane crosslinker, a condensation catalyst, a filler, and the like. Examples of condensation-curable silyl-terminated polymers include polydialkylsiloxanes, alkylphenylsiloxanes, organic polymers having silyl groups (e.g., silyl polyethers, silyl acrylates), and polyisobutylenes having silyl groups. Examples of silane crosslinkers include alkoxy-functional silanes, oximosilanes, acetoxysilanes, and enoxysilanes. Examples of fillers include iron oxide, titanium dioxide, carbon black, and talc. Examples of condensation catalysts include titanates and zirconates. These condensation-curable silyl-terminated polymers, silane crosslinkers, condensation catalysts, and fillers are stored in a first and second liquid form in a combination that does not promote a curing reaction, and are mixed when used.

[0044] In the pneumatic tire, it is preferable that the storage modulus G' of the sealant at 100°C is 20 kPa or less. When the storage modulus G' of the sealant at 100°C is small, vibration of the sealant layer 20 is suppressed, improving ride comfort. If the storage modulus G' of the sealant at 100°C is greater than 20 kPa, the effect of improving ride comfort decreases. In particular, it is preferable that the storage modulus G' of the sealant at 100°C is in the range of 5 kPa to 15 kPa.

[0045] In the above pneumatic tire, it is preferable that the loss modulus G" of the sealant at 100°C is 5 kPa or less. When the sealant has a small loss modulus G" at 100°C, heat generation in the sealant layer 20 is suppressed, thereby reducing the impact on durability. If the loss modulus G" of the sealant at 100°C is greater than 5GP, the effect of improving durability decreases. In particular, it is preferable that the loss modulus G" of the sealant at 100°C is in the range of 1 kPa to 3 kPa.

[0046] In the pneumatic tire described above, the thickness S of the sealant layer 20 is preferably in the range of 2.0 mm to 5.0 mm, as shown in FIG. 2 . This ensures puncture sealing performance while suppressing deterioration in 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 decreased 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 a tire meridian cross section at eight locations around the tire circumference, 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.

[0047] In the above pneumatic tire, as shown in Fig. 2, it is preferable that the distance (shortest distance) L from the belt layer 7A located at the innermost position 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.

[0048] 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, the puncture sealing performance deteriorates.

[0049] In the above-described pneumatic tire, multiple belt layers 7 are embedded in the tread portion 1. The belt layers 7 include belt cords that are inclined relative to the tire circumferential direction and are arranged so that the belt cords cross each other between the layers. When these belt layers 7 include a first belt layer 7A located at the innermost position in the tire radial direction and a second belt layer 7B located at the outermost position in the tire radial direction, 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 7B located at the outermost position in the tire radial direction. In particular, it is preferably that the end of the sealant layer 20 is 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 7B, good sealing performance can be ensured.

[0050] FIG. 8 shows a pneumatic tire according to another embodiment of the present invention. In FIG. 8, a sound-absorbing material 40 is disposed 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 properties 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 based on the adhesiveness of the sealant layer 20. In particular, when the sealant of the sealant layer 20 is composed of a silicone-based composition, the sound-absorbing material 40 is disposed on the sealant layer 20, which is applied at a low temperature, thereby avoiding damage to the sound-absorbing material 40 and maintaining its sound-absorbing effect. [Example]

[0051] 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, on whose inner surface a bladder transfer pattern including a plurality of ridges extending in the tire width direction is formed, and on whose inner surface a release agent is applied, is formed a sealant layer having a structure in which a strip of sealant is spirally arranged along the tire circumferential direction on the inner surface of the tread portion of the tire, and tires of Comparative Examples 1-2 and Examples 1-5 are produced in which the constituent materials of the sealant layer, the width L1 of the sealant strip, the spacing L2 of the ridges in the tire width direction, the ratio L1 / L2, the number of ridges overlapping with the ends of the strip, and the distance D from the convex portions formed on the inner surface of the tire due to the splice of the inner liner layer to the ends of the sealant strip are varied as shown in Table 1. A two-component curing silicone was used as the silicone composition for the sealant, and the storage modulus G' at 100°C was 10 kPa, and the loss modulus G" at 100°C was 3 kPa. The thickness S of the sealant layer was 3.5 mm.

[0052] The adhesion of the sealant layer and the ride comfort of these test tires were evaluated by the following test methods. The results are also shown in Table 1.

[0053] Sealant layer adhesion: Each test tire was mounted on a wheel with a rim size of 19 x 8.5J and attached to a drum testing machine equipped with 9.5 mm high cleats on the outer periphery of the drum. A running test was conducted under conditions of 140 kPa air pressure, 100% of the maximum load capacity, a speed of 60 km / h, and a distance of 1,000 km. After the test, the percentage of peeling within a 100 mm range from the edge of the sealant strip was measured. The evaluation results were indicated as follows: a peeling percentage of 0% was indicated as "○ (pass)," a peeling percentage of less than 5% was indicated as "△ (pass)," and a peeling percentage of 5% or more was indicated as "× (fail)."

[0054] Ride comfort: Each test tire was mounted on a 19x8.5J rim wheel and mounted on a 2400cc class test vehicle, with the air pressure set to 210kPa and the load set to 100% of the maximum load capacity, and a sensory evaluation was conducted by a test driver on a paved test course. The evaluation results were expressed as an index, with a tire without a sealant layer being set at 100. The higher the index value, the better the ride comfort.

[0055] [Table 1]

[0056] As can be seen from Table 1, the tires of Examples 1 to 5 had good adhesion of the sealant layer to the tire inner surface. In contrast, the tire of Comparative Example 1 used a sealant made of butyl rubber, and therefore had poor adhesion of the sealant layer to the tire inner surface. Furthermore, the tire of Comparative Example 2 had poor adhesion of the sealant layer to the tire inner surface because the width L1 of the sealant strip was larger than the spacing L2 of the ridges in the tire width direction.

[0057] The present disclosure includes the following inventions [1] to

[10] . Invention [1] is a pneumatic tire comprising a tread portion extending in the tire circumferential direction and forming an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on the tire radially inward side of the sidewall portions, in which a bladder transfer pattern including a plurality of protrusions extending in the tire width direction is formed on the tire inner surface, and a release agent is applied to the tire inner surface, The pneumatic tire is characterized in that a sealant layer having a structure in which a strip of sealant is spirally arranged along the tire circumferential direction is formed on the inner surface of the tire in the tread portion, the sealant is made of a silicone-based composition, and a width L1 of the strip and a spacing L2 between the ridges in the tire width direction satisfy the relationship L1≦L2. Invention [2] is a pneumatic tire according to invention [1], characterized in that the width L1 of the strip material satisfies the relationship 0.2≦L1 / L2≦0.7 with respect to the spacing L2 of the ridges in the tire width direction. Invention [3] is a pneumatic tire according to invention [1] or [2], characterized in that both ends of the strip material are positioned so as not to overlap with the protrusions. Invention [4] is a pneumatic tire according to any one of inventions [1] to [3], characterized in that in a pneumatic tire in which a convex portion caused by a splice of tire constituent members is formed on the inner surface of the tire, both ends of the strip material are positioned so as not to overlap the convex portion. Invention [5] is a pneumatic tire according to invention [4], characterized in that both end portions of the strip material are positioned at a distance of 5 mm or more from the convex portion. Invention [6] is the pneumatic tire according to invention [4] or [5], characterized in that the tire constituent member is an inner liner layer. Invention [7] is the pneumatic tire according to any one of inventions [1] to [6], characterized in that the storage modulus G' of the sealant at 100° C. is 20 kPa or less. Invention [8] is the pneumatic tire according to any one of inventions [1] to [7], characterized in that the loss modulus G" of the sealant at 100°C is 5 kPa or less. Invention [9] is the pneumatic tire according to any one of inventions [1] to [8], characterized in that the thickness of the sealant layer is in the range of 2.0 mm to 5.0 mm. An invention

[10] is the pneumatic tire according to any one of inventions [1] to [9], characterized in that the silicone composition is a two-component curing silicone. [Explanation of symbols]

[0058] 1 Tread section 2 Sidewall 3 Bead section 4 carcass layers 5 bead core 6 Bead filler 7 Belt Layer 8 Belt cover layer 9 Inner liner layer 9s convex part 9g protrusion 10 Tire inner surface 20 Sealant Layer 21 Sealant Strip E1, E2 End of strip material

Claims

1. A pneumatic tire comprising a tread portion extending in a tire circumferential direction to form an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on the tire radially inward side of the sidewall portions, wherein a bladder transfer pattern including a plurality of protrusions extending in the tire width direction is formed on the tire inner surface, and a release agent is applied to the tire inner surface, a sealant layer having a structure in which a strip of sealant is spirally arranged along the tire circumferential direction formed on the tire inner surface in the tread portion, the sealant being composed of a silicone-based composition, and a width L1 of the strip of sealant relative to a spacing L2 of the protrusions in the tire width direction satisfying the relationship L1≦L2.

2. 2. The pneumatic tire according to claim 1, wherein the width L1 of the strip material and the spacing L2 of the ridges in the tire width direction satisfy the relationship 0.2≦L1 / L2≦0.

7.

3. 3. The pneumatic tire according to claim 1, wherein both end portions of the strip material are arranged in positions that do not overlap with the ridges.

4. 2. The pneumatic tire according to claim 1, wherein a convex portion caused by a splice of tire constituent members is formed on the inner surface of the tire, and both end portions of the strip material are arranged in positions that do not overlap the convex portion.

5. 5. The pneumatic tire according to claim 4, wherein both end portions of the strip material are positioned at a distance of 5 mm or more from the protruding portion.

6. The pneumatic tire according to claim 4 or 5, wherein the tire component is an inner liner layer.

7. 3. The pneumatic tire according to claim 1, wherein the sealant has a storage modulus G' at 100° C. of 20 kPa or less.

8. 3. The pneumatic tire according to claim 1, wherein the sealant has a loss modulus G" at 100°C of 5 kPa or less.

9. 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.

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

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