Pneumatic tire and method for manufacturing the same

Abstract

To provide a pneumatic tire which enhances adhesion between a tire inner surface and a sealant layer, and can improve durability of a tire, and a method for manufacturing the same.SOLUTION: A pneumatic tire includes a tread part 1 which extends in a tire circumferential direction and forms an annular shape, a pair of side wall parts 2 arranged on both sides of the tread part 1, and a pair of bead parts 3 arranged inside in a tire radial direction of the side wall parts 2, where a sealant layer 20 is formed on a tire inner surface Ts in the tread part 1; the sealant of the sealant layer 20 is composed of a silicone-based composition; and an amount of silicon of a release agent in at least an arrangement region of the sealant layer 20 is 10.0% or less, or thickness of the release agent in at least the arrangement region of the sealant layer 20 is 100 μm or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a pneumatic tire having a sealant layer on the inner surface of the tire in the tread portion and a method for manufacturing the same, and more particularly to a pneumatic tire and a method for manufacturing the same that enhance the adhesion between the inner surface of the tire and the sealant layer and improve the durability of the tire.

Background Art

[0002] As a pneumatic tire having puncture sealing properties, a tire having a sealant layer made of an adhesive sealant disposed on the inner surface of the tire in the tread portion has been proposed (for example, Patent Document 1). In such a pneumatic tire provided with a sealant layer, when a foreign object such as a nail pierces the tread portion, the adhesive sealant adheres to the foreign object, and as the foreign object falls off, the adhesive sealant is guided to the puncture hole to exhibit a sealing effect.

[0003] On the other hand, in the manufacturing process of a pneumatic tire, when vulcanizing a green tire using a bladder, since the bladder easily adheres to the inner surface of the green tire, a release agent is applied to the inner surface of the green tire to prevent the adhesion between the green tire and the bladder. However, when a large amount of the release agent remains on the inner surface of the tire after vulcanization, there is a problem that the adhesion to the inner surface of the tire is low depending on the type of the sealant of the sealant layer disposed on the inner surface of the tire, which adversely affects the durability of the tire.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of the present invention is to provide a pneumatic tire and a method for manufacturing the same, which can enhance the adhesion between the inner surface of the tire and the sealant layer and improve the durability of the tire.

Means for Solving the Problems

[0006] 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 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. In the pneumatic tire, a sealant layer is formed on the inner surface of the tire in the tread portion, the sealant of the sealant layer is composed of a silicone-based composition, and the amount of silicon of the release agent in at least the arrangement region of the sealant layer is 10.0% or less.

[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 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. In the pneumatic tire, a sealant layer is formed on the inner surface of the tire in the tread portion, the sealant of the sealant layer is composed of a silicone-based composition, and the thickness of the release agent in at least the arrangement region of the sealant layer is 100 μm or less.

[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 the pneumatic tire excluding the sealant layer, when applying a sealant composed of a silicone-based composition 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 set to 70°C or less.

Effects of the Invention

[0009] In the present invention, since the amount of silicon in the release agent in at least the area where the sealant layer is disposed is 10.0% by weight or less, or the thickness of the release agent is 100 μm or less, the release agent adheres in a very small amount or not at all to the inner surface of the tire. Therefore, the risk of cohesive failure of the release agent or interfacial peeling between the release agent and the tire can be reduced on the inner surface of the tire. Moreover, since the sealant of the sealant layer is composed of a silicone-based composition, when the release agent adhering to the inner surface of the tire contains the silicone-based composition, they are likely to adhere to each other, so peeling of the sealant layer hardly occurs. Also, when no release agent adheres to the inner surface of the tire, the sealant layer adheres directly to the inner surface of the tire and is firmly fixed, so peeling of the sealant layer hardly occurs. Further, since a sealant layer containing a sealant composed of a silicone-based composition is formed, it is possible to lower the temperature of the sealant applied to the inner surface of the tire. Therefore, the influence of heat on the tire can be reduced, and deterioration of durability can be avoided. In this way, the adhesiveness between the inner surface of the tire and the sealant layer can be enhanced, and the durability of the tire can be improved.

[0010] In the pneumatic tire of the present invention, it is preferable that the adhesive strength of the sealant layer is in the range of 0.1 N / mm to 10.0 N / mm. While sufficiently ensuring the adhesiveness of the sealant layer during use, separation between the sealant layer and the inner surface of the tire during disposal can be enabled, and the disposal work can be easily performed.

[0011] At all locations of the belt layer located at the innermost side in the tire radial direction, the distance L from the belt layer to the sealant layer is preferably 10 mm or less. Thereby, when a foreign object such as a nail penetrates the tread portion, the sealant easily flows to the belt layer, so good puncture sealing performance can be ensured.

[0012] The thickness of the sealant layer is preferably in the range of 2.0 mm to 5.0 mm. Thereby, in addition to the shoulder portion, puncture sealing performance at the center portion can be sufficiently ensured.

[0013] The silicone-based composition constituting the sealant 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.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0015] Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. FIGS. 1 and 2 show a pneumatic tire according to an embodiment of the present invention.

[0016] 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 disposed on both sides of the tread portion 1, and a pair of bead portions 3 disposed on the inner side in the tire radial direction of these sidewall portions 2.

[0017] Between the pair of bead portions 3, at least one layer (one layer in FIG. 1) of carcass layer 4 formed by arranging a plurality of carcass cords in the radial direction is mounted. As the carcass cords constituting the carcass layer 4, organic fiber cords such as nylon and polyester are preferably used. An annular bead core 5 is embedded in each bead portion 3, and 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.

[0018] On one hand, on the outer peripheral side of the carcass layer 4 in the tread portion 1, a plurality of layers (two layers in FIG. 1) of belt layers 7 are embedded. The belt layer 7 includes a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and the reinforcing cords are arranged so as to cross each other between the layers. In the belt layer 7, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is set, for example, in the range of 10° to 40°. As the reinforcing cord of the belt layer 7, a steel cord is preferably used.

[0019] On the outer peripheral side of the belt layer 7, for the purpose of improving high-speed durability, at least one layer (two layers in FIG. 1) of belt cover layer 8 is arranged in which the 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, an organic fiber cord such as nylon or aramid is preferably used.

[0020] Note that the above-described tire internal structure shows a typical example in a pneumatic tire, but is not limited thereto. As a member constituting the tire inner surface Ts, an inner liner layer 9 is arranged along the carcass layer 4.

[0021] In the above pneumatic tire, a sealant layer 20 is formed on the inner surface Ts 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 in the tire width direction 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 balance of the tire. Further, 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.

[0022] In at least the arrangement region of the sealant layer 20 on the inner surface Ts of the tire, the amount of silicon in the release agent is 10.0% by weight or less. In the present invention, when defining the amount of the release agent on the inner surface Ts of the tire, the amount of silicon, which is the main component of a general release agent, is used as an index. The amount of this silicon can be detected using the fluorescent X-ray analysis method. Generally, the fluorescent X-ray analysis method includes the FP method (fundamental parameter method) and the calibration curve method, but the FP method is adopted in the present invention. When measuring the amount of the release agent (silicon), sheet samples (dimensions: width 70 mm, length 100 mm) obtained by peeling the carcass layer and the inner liner layer at a plurality of locations (for example, a total of 7 locations including 4 locations in the tire circumferential direction and 3 locations in the tire width direction) of the pneumatic tire are used, and a total of 5 measurement samples (dimensions: width 13 mm to 15 mm, length 35 mm to 40 mm) including 4 corner locations and 1 center location are extracted from each sheet sample, and the amount of the release agent is measured for each measurement sample using a fluorescent X-ray analyzer. Then, the amount of the release agent for each sheet sample is calculated by averaging the measured values of the 5 measurement samples for each sheet sample, and the calculated value is 10.0% by weight or less for each. Further, fluorescent X-ray particles have a unique energy proportional to the atomic number, and it becomes possible to identify an element by measuring this unique energy. Specifically, the unique energy of silicon is 1.74 ± 0.05 keV. Note that the number of fluorescent X-ray particles (X-ray intensity) of the release agent (silicon) is in the range of 0.1 cps / μA to 1.5 cps / μA.

[0023] Alternatively, in at least the arrangement region of the sealant layer 20 on the inner surface Ts of the tire, the thickness g (see FIG. 2) of the release agent is 100 μm or less. The thickness g of this release agent can be detected using an electron microscope. When measuring the thickness g of the release agent with an electron microscope, a sample cut out from the pneumatic tire along the tire width direction is used, and the thicknesses at a plurality of locations (for example, 4 locations in the tire circumferential direction and 3 locations in the tire width direction) are measured in the sample. Then, the thickness g (average thickness) of the release agent is calculated by averaging the measured values measured at the plurality of locations.

[0024] The mold release agent adhered to the inner surface Ts of the tire preferably contains a silicone-based composition. The silicone-based composition includes, for example, a synthetic polymer compound having a main skeleton formed by siloxane bonds.

[0025] In FIG. 2, a mold release layer 10 made of a mold release agent is formed on the inner side in the tire radial direction of the tire inner surface Ts, and the mold release agent is adhered to the tire inner surface Ts. That is, the sealant layer 20, the mold release layer 10, and the tire inner surface Ts (inner liner layer 9) are laminated in this order from the inner side in the tire radial direction. Alternatively, as shown in FIG. 5, the mold release layer 10 may not be formed on the tire inner surface Ts, and the structure may be such that no mold release agent adheres to the tire inner surface Ts. That is, the sealant layer 20 and the tire inner surface Ts (inner liner layer 9) are laminated in this order from the inner side in the tire radial direction. In this case, the mold release agent is not applied or transferred to the tire inner surface Ts in the vulcanization process, or the mold release agent is completely removed from the tire inner surface Ts after vulcanization.

[0026] In the above-mentioned pneumatic tire, since at least the amount of silicon in the release agent in the arrangement region of the sealant layer 20 is 10.0% by weight or less, or the thickness of the release agent is 100 μm or less, the release agent adheres to the tire inner surface Ts in a very small amount or not at all. Therefore, the risk of cohesive failure of the release agent or interfacial peeling between the release agent and the tire can be reduced on the tire inner surface Ts. Moreover, since the sealant of the sealant layer 20 is composed of a silicone-based composition, when the release agent adhering to the tire inner surface Ts contains a silicone-based composition, they are likely to adhere to each other, so the peeling of the sealant layer 20 is less likely to occur. Also, when the release agent does not adhere to the tire inner surface Ts at all, the sealant layer 20 is directly adhered to the tire inner surface Ts and firmly fixed, so the peeling of the sealant layer 20 is less likely to occur. In addition, since the sealant layer 20 containing a sealant composed of a silicone-based composition is formed, it is possible to lower the temperature of the sealant applied to the tire inner surface Ts. Therefore, the influence of heat on the tire can be reduced, and the deterioration of durability can be avoided. In this way, the adhesiveness between the tire inner surface Ts and the sealant layer 20 can be enhanced, and the durability of the tire can be improved.

[0027] On the contrary, for example, when the sealant of the sealant layer is made of butyl rubber or natural rubber and the release agent adhering to the tire inner surface contains a silicone-based composition, since their components are different, sufficient adhesiveness cannot be ensured, and the peeling of the sealant layer is likely to occur. Also, when using butyl rubber or natural rubber generally used as a sealant, in the process of arranging the sealant on the tire inner surface, the sealant in a softened state heated to a high temperature is applied to the tire inner surface. Therefore, the tire constituent members embedded in the tread portion are deteriorated by the influence, and as a result, the tire performance such as durability tends to deteriorate.

[0028] In the above-mentioned pneumatic tire, the adhesive strength of the sealant layer 20 to the inner surface Ts of the tire is preferably in the range of 0.1 N / mm to 10.0 N / mm. While sufficiently ensuring the adhesiveness of the sealant layer 20 during use, it enables the separation of the sealant layer 20 from the inner surface Ts of the tire during disposal, and the disposal work can be easily carried out. Here, if the adhesive strength of the sealant layer 20 is less than 0.1 N / mm, the risk of the sealant layer 20 falling off during driving increases. Conversely, if it exceeds 10.0 N / mm, it becomes difficult to peel the sealant layer 20 from the inner surface Ts of the tire during disposal. The adhesive strength of the sealant layer is based on the 90° peel test in JIS Z0237. A cut sample is prepared from a tire having a sealant layer on the inner surface, and the sealant is peeled off from the inner surface of the cut sample at a peel rate of 50 mm / min, and the adhesive strength (peel strength) at that time is measured.

[0029] Also, the thickness S of the sealant layer 20 (see Figure 2) is preferably in the range of 2.0 mm to 5.0 mm. Thereby, in addition to the shoulder portion, the puncture sealing performance at the center portion can be sufficiently ensured. Here, if the thickness S of the sealant layer 20 is less than 2.0 mm, the puncture sealing performance deteriorates. Conversely, if it is greater than 5.0 mm, the sealant layer 20 flows due to the centrifugal force of the tire during driving, and the balance of the tire during driving deteriorates. 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. In each of the photographed images, the thickness of the sealant layer 20 is measured at 5 points, namely, the tire equator position, the outer edge positions (both sides) 10 mm inward in the tire width direction from the end of the sealant layer 20, and the intermediate positions (both sides) between the tire equator position and the outer edge positions, and is calculated from the measurement values at a total of 40 points.

[0030] In the above pneumatic tire, as shown in FIG. 2, it is preferable that the distance (shortest distance) L from the belt layer 7 to the sealant layer 20 is 10 mm or less at all positions of the belt layer 7 located at the innermost side in the tire radial direction. Thereby, when a foreign object such as a nail penetrates the tread portion 1, the sealant easily flows to the belt layer 7, so that good puncture sealing performance can be ensured. If there is a portion where the distance L from the belt layer 7 to the sealant layer 20 is greater than 10 mm, the puncture sealing performance in that portion may become insufficient.

[0031] In the above pneumatic tire, the belt cover layer 8 may cover only a part of the belt layer 7 in the tire width direction (for example, the edge portions on both sides of the belt layer in the tire width direction), but it is preferable that it covers the entire area of the belt layer 7 in the tire width direction. Thereby, the durability of the tire can be further improved, and even when a nail is punctured, the amount of air leakage at the shoulder portion can be suppressed, so that the puncture sealing performance can be further improved. In the embodiment of FIG. 1, the belt cover layer 8 located on the inner side in the tire radial direction constitutes a full cover that covers the entire area of the belt layer 7, and the belt cover layer 8 located on the outer side in the tire radial direction constitutes an edge cover that covers only the edge portions of the belt layer 7.

[0032] Next, a method for manufacturing a pneumatic tire of the present invention will be described. Through the vulcanization process described later, a pneumatic tire having the tread portion 1, a pair of sidewall portions 2, and a pair of bead portions 3 as described above is manufactured. Next, a sealant made of a silicone-based composition is applied to the tire inner surface Ts in the tread portion 1 to form a sealant layer 20. At this time, since the silicone-based composition has good fluidity even at low temperatures, the temperature of the sealant applied to the tire inner surface Ts is set to 70 °C or lower. If this temperature exceeds 70 °C, in the process of applying the sealant to the tire inner surface Ts, the distortion generated in the pneumatic tire becomes large, and the durability of the tire deteriorates. In particular, the temperature of the sealant when applying the sealant to the tire inner surface Ts is preferably in the range of 5 °C to 40 °C, more preferably in the range of 10 °C to 35 °C, and most preferably in the range of 15 °C to 30 °C. Thereby, the over-vulcanization of the rubber member due to heating during the formation of the sealant layer 20 is suppressed. Further, when the mold release agent constituting the mold release layer 10 contains a silicone-based composition, since the sealant layer 20 contains a similar material, the two are easily compatible, and the sealant layer 20 can be well adhered to the tire inner surface Ts.

[0033] FIG. 3 shows a specific manufacturing method of a pneumatic tire according to an embodiment of the present invention, and FIG. 4 shows a sealant layer formed on the tire inner surface in the tread portion. In FIG. 3, the sealant extruding device 31 mixes the sealant supplied from the pumps 32 and 33, and continuously discharges the mixed sealant from the nozzle 34 as a strip material 21. The 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 tire inner surface, the strip material 21 of the sealant can be spirally arranged on the tire inner surface while being inclined with respect to the tire circumferential direction Tc (see FIG. 4). 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.

[0034] As the silicone-based composition constituting the sealant of the sealant layer 20, one-part curable silicone or two-part curable silicone can be used, but it is particularly preferable to use two-part curable silicone. Examples of the one-part curable silicone include moisture curable silicone. The two-part curable silicone is composed of a first liquid and a second liquid. By mixing these first and second liquids, the curing reaction starts, and 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-part curable silicone are supplied from pumps 32 and 33, respectively. Since the two-part curable silicone has a low viscosity immediately after the two liquids are mixed, it can be applied even at a low temperature.

[0035] The two-part 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.

[0036] Also, regarding the vulcanization process, the vulcanization method of the green tire is not particularly limited. For example, (a) vulcanizing the green tire using a bladder provided with a coating layer made of a release agent, (b) vulcanizing the green tire using a core instead of a bladder, or (c) vulcanizing the green tire using a normal bladder can be mentioned. In the case of (a) above, it is possible to slightly adhere or not adhere any release agent to the inner surface Ts of the tire after vulcanization. In the case of (b) above, since a release agent is not required, there is no release agent on the inner surface Ts of the tire after vulcanization. On the other hand, in the case of (c) above, a large amount of release agent adheres to the inner surface Ts of the tire after vulcanization, but buffing or laser treatment is performed on the inner surface Ts of the tire after vulcanization, or a film is previously attached to the inner surface of the green tire before vulcanization, and a release agent is applied to the inner surface of the green tire with the film attached, and then the film is peeled off after vulcanizing the green tire using a normal bladder, so that the release agent on the inner surface Ts of the tire can be completely removed.

[0037] Also, in the case of (a) above, since the cycle time during production can be shortened, the productivity of the tire can be improved, which is preferable. In the case of (a) above, a release agent is previously coated (preferably baked) on the bladder to form a coating layer made of a release agent on the outer surface of the bladder. The step of forming the coating layer on the outer surface of this bladder is carried out, for example, while storing under the conditions of 150°C for 1 hour and 90°C for 4 hours after applying the release agent. Also, the step of forming the coating layer on the outer surface of the bladder is carried out in the range of 1 to 3 times. When the green tire is vulcanized using the bladder thus formed with the coating layer, and if the release agent is transferred to the inner surface Ts of the tire after vulcanization, a release layer 10 (transfer layer) made of a release agent will be formed on the inner surface Ts of the tire, but the release agent is not transferred to the entire surface of the inner surface Ts of the tire and is scattered.

[0038] Particularly, in the step of forming the coating layer on the outer surface of the bladder, the coating time t (hour) and temperature T (°C) of the coating layer satisfy t ≧ 0.00005T 2It is preferable to satisfy the condition of -0.063T + 9.24 and T ≤ 180°C. Further, while satisfying the relational expression between the coating time t and the temperature T described above, it is more preferable that the coating time t is in the range of 1 to 8 hours and T ≤ 160°C is satisfied. Furthermore, it is more preferable that the temperature T is 90°C and the coating time t is 4 hours, and it is most preferable that the temperature T is 150°C and the coating time t is 1 hour. By satisfying such conditions, in the bladder having the coating layer, the time for coating the release agent can be shortened and the shortening of the bladder life can be prevented. Here, the higher the temperature T (°C), the shorter the time for forming the coating layer, but the bladder is likely to deteriorate and the bladder life is shortened.

Example

[0039] 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 is formed on the inner surface of the tire in the tread portion, and the amount of silicon in the release agent, the type of sealant, the adhesive strength of the sealant layer, the distance L, and the thickness of the sealant layer are set as shown in Table 1. Tires of Comparative Examples 1 and 2 and Examples 1 to 10 were manufactured.

[0040] In Table 1, when a release agent is present, the release agent contains a silicone-based composition. Also, in Table 1, the amount of the release agent (silicon) adhered to the inner surface of the tire is the average of the calculated values calculated based on the amounts of the release agent (silicon) measured at 4 locations in the tire circumferential direction and 3 locations in the tire width direction of each test tire after the manufacturing process using an energy dispersive X-ray fluorescence analyzer (EDX-720 manufactured by Shimadzu Corporation). The measurement conditions are a vacuum state, a voltage of 50 kV, a current of 100 μA, an integration time of 50 seconds, and a collimator φ10 mm.

[0041] For these test tires, durability, sealant fluidity, and puncture sealing performance were evaluated by the following test methods, and the results are shown together in Table 1.

[0042] Durability: Each test tire was assembled onto a wheel with a rim size of 19×8.5J, and a running test was carried out on a drum tester under the conditions of an air pressure of 120 kPa, 100% of the maximum load, and a running speed of 80 km / h. The running distance until a failure occurred in the tire was measured. The evaluation results were shown in an index with Comparative Example 1 set as 100. The larger this index value is, the better the durability.

[0043] Sealant fluidity: Each test tire was assembled onto a wheel with a rim size of 19×8.5J, and a running test was carried out on a drum tester under the conditions of an air pressure of 260 kPa and 80% of the maximum load. Specifically, starting from the stopped state, the speed was increased by 3 km / h every 30 minutes. After reaching 185 km / h, it was run for 30 minutes, and the state of the end part of the sealant layer in the tire width direction was visually confirmed. The evaluation results were indicated by "〇" when the end part of the sealant layer in the tire width direction did not flow, and "×" when the end part of the sealant layer in the tire width direction flowed.

[0044] Puncture sealing property: Each test tire was assembled onto a wheel with a rim size of 19×8.5J and mounted on a vehicle with a displacement of 2400 cc. The initial air pressure was set at 230 kPa. A nail with a diameter of 5 mm was driven into the center of the tread part. After running for 10 km, the tire was left for 24 hours with the nail pulled out, and the air pressure was measured again. The evaluation results were indicated by "◎(excellent)" when the air pressure was 210 kPa or more, "〇(good)" when the air pressure was 190 kPa or more and less than 210 kPa, and "△(fair)" when the air pressure was less than 190 kPa.

[0045]

Table 1

[0046] As can be seen from Table 1, the pneumatic tires of Examples 1 to 10 had improved durability compared to Comparative Example 1. In contrast, in Comparative Example 2, since the components of the sealant and the mold release agent were different from each other, sufficient adhesiveness could not be ensured, and the durability deteriorated.

[0047] 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 is formed on the inner surface of the tire in the tread portion, and the thickness of the release agent, the type of sealant, the adhesive strength of the sealant layer, the distance L, and the thickness of the sealant layer are set as shown in Table 2. Tires of Comparative Examples 3 and 4 and Examples 11 to 20 were manufactured.

[0048] In Table 2, when a release agent is present, the release agent contains a silicone-based composition. Also, in Table 2, the thickness [μm] of the release agent adhered to the inner surface of the tire is the average of the thicknesses of the release agent measured at four locations in the tire circumferential direction and three locations in the tire width direction of each test tire after the manufacturing process using a scanning electron microscope (SEM-EDX).

[0049] These test tires were evaluated for durability, sealant fluidity, and puncture sealing performance, and the results are shown together in Table 2. In Table 2, the evaluation results of durability are shown as an index with Comparative Example 3 as 100.

[0050]

Table 2

[0051] As can be seen from this Table 2, in Examples 10 to 20, the durability was improved compared to Comparative Example 3. On the other hand, in Comparative Example 4, since the components of the sealant and the release agent were different from each other, sufficient adhesiveness could not be ensured, and the durability deteriorated.

[0052] This disclosure includes the following inventions [1] to [7]. The invention [1] relates to 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 radial direction inner side of these sidewall portions. In the pneumatic tire, a sealant layer is formed on the inner surface of the tire in the tread portion, the sealant of the sealant layer is composed of a silicone-based composition, and the amount of silicon of the release agent in at least the arrangement region of the sealant layer is 10.0% or less. The invention [2] relates to 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 radial direction inner side of these sidewall portions. In the pneumatic tire, a sealant layer is formed on the inner surface of the tire in the tread portion, the sealant of the sealant layer is composed of a silicone-based composition, and the thickness of the release agent in at least the arrangement region of the sealant layer is 100 μm or less. The invention [3] is the pneumatic tire according to invention [1] or [2], characterized in that the adhesive strength of the sealant layer is in the range of 0.1 N / mm to 10.0 N / mm. The invention [4] is the pneumatic tire according to any one of inventions [1] to [3], characterized in that at all locations of the belt layer located at the innermost side in the tire radial direction, the distance L from the belt layer to the sealant layer is 10 mm or less. The invention [5] is the pneumatic tire according to any one of inventions [1] to [5], characterized in that the thickness of the sealant layer is in the range of 2.0 mm to 5.0 mm. The invention [6] is the pneumatic tire according to any one of inventions [1] to [5], characterized in that the silicone-based composition constituting the sealant is a two-component curable silicone. The invention [7] is a method for manufacturing a pneumatic tire according to any one of inventions [1] to [6], wherein after manufacturing a pneumatic tire excluding the sealant layer, when forming the sealant layer by applying a sealant composed 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 set to 70 °C or lower.

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 10 Release layer 20 Sealant layer Ts Inner surface of the tire

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 sealant layer is formed on the inner surface of the tire in the tread portion, the sealant of the sealant layer is composed of a silicone-based composition, and the amount of silicon of the release agent in at least the arrangement region of the sealant layer is 10.0% or less. A pneumatic tire characterized by this.

2. 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 sealant layer is formed on the inner surface of the tire in the tread portion, the sealant of the sealant layer is composed of a silicone-based composition, and the thickness of the release agent in at least the arrangement region of the sealant layer is 100 μm or less. A pneumatic tire characterized by this.

3. The pneumatic tire according to claim 1 or 2, wherein the adhesive strength of the sealant layer is in the range of 0.1 N / mm to 10.0 N / mm.

4. The pneumatic tire according to claim 1 or 2, wherein at all locations of the belt layer located at the innermost side in the tire radial direction, the distance L from the belt layer to the sealant layer is 10 mm or less.

5. 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.

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

7. A method for manufacturing the 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 composed 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 set to 70° C. or lower. A method for manufacturing a pneumatic tire characterized by this.

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