Pneumatic tire and method for manufacturing the same

Abstract

Provided are a pneumatic tire and a method for manufacturing the same, which make it possible to enhance the adhesion between the inner surface of the tire and the sealant layer and improve the durability of the tire. In a pneumatic tire including a tread portion 1 extending in the circumferential direction of the tire and forming 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 radial direction of the tire of these sidewall portions 2, the inner surface Ts of the tire has a release layer 10 containing a silicone-based composition, a sealant layer 20 is formed on the inner side in the radial direction of the tire of the release layer 10 in the tread portion 1, the sealant of the sealant layer 20 is composed of a silicone-based composition, and the absolute value of the difference between the contact angle of water with respect to the release layer 10 and the contact angle of water with respect to the sealant layer 20 is 30° or less.

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 enable improvement of the adhesion between the inner surface of the tire and the sealant layer and improvement of 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 drops 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 the compatibility between the inner surface of the tire to which the release agent has adhered and the sealant layer is low, they do not mix well and the adhesion between the inner surface of the tire and the sealant layer is low, which causes a problem of adversely affecting 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 that 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 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. The tire has a release layer containing a silicone-based composition on the inner surface of the tire, a sealant layer is formed on the inner side in the tire radial direction of the release layer in the tread portion, the sealant of the sealant layer is composed of a silicone-based composition, and the absolute value of the difference between the contact angle of water with respect to the release layer and the contact angle of water with respect to the sealant layer is 30° or less.

[0007] 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 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 less.

Effects of the Invention

[0008] The inventor of the present invention has found that when enhancing the adhesion between the inner surface of the tire and the sealant layer, it is effective to use the contact angle of water as an index of the compatibility between members and set the absolute value of the difference in the contact angle within a specific range, and thus the present invention has been achieved.

[0009] In the present invention, a release layer containing a silicone-based composition is provided on the inner surface of the tire, a sealant layer is formed on the inner side in the tire radial direction of the release layer in the tread portion, and the sealant of the sealant layer is composed of a silicone-based composition. Therefore, since both the release layer and the sealant layer contain a silicone-based composition, it contributes to improving compatibility. Furthermore, by setting the absolute value of the difference between the contact angle of water with respect to the release layer and the contact angle of water with respect to the sealant layer within a specific range (30° or less), the compatibility can be made very good. Thereby, 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 thickness of the release layer is in the range of 0.1 μm to 100.0 μm. Thereby, the durability of the tire can be effectively improved.

[0011] It is preferable that the glass transition temperature of the sealant is in the range of -120°C to -40°C. By using a sealant with a low glass transition temperature, the puncture sealing performance under low-temperature environments can be ensured well.

[0012] 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.

[0013] At all locations of the belt layer located on the innermost side in the tire radial direction, it is preferable that the distance L from the 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 to the belt layer, so that good puncture sealing performance can be ensured.

[0014] 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 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

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

BEST MODE FOR CARRYING OUT THE INVENTION

[0016] 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.

[0017] 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.

[0018] 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 between the pair of bead portions 3. 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.

[0019] On one hand, on the outer tire 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 in the range of, for example, 10° to 40°. As the reinforcing cord of the belt layer 7, a steel cord is preferably used.

[0020] On the outer tire 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 in which the reinforcing cords are arranged at an angle of, for example, 5° or less with respect to the tire circumferential direction is arranged. This belt cover layer 8 preferably 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.

[0021] 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.

[0022] In the above pneumatic tire, a release layer 10 formed by applying or transferring a release agent is formed on the inner tire side in the tire radial direction of the tire inner surface Ts. The release layer 10 contains a silicone-based composition. The silicone-based composition includes, for example, a synthetic polymer compound having a main skeleton formed by a siloxane bond.

[0023] Further, a sealant layer 20 is formed so as to be continuous in the tire circumferential direction on the inner side in the tire radial direction of the release layer 10 in the tread portion 1. That is, the sealant layer 20, the 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. The center position of the sealant layer 20 in the tire width direction preferably coincides with the tire equator, but the center position may be shifted 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. 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 by a siloxane bond.

[0024] In such a release layer 10 and sealant layer 20, the contact angle θ of water with respect to the release layer 10 10 and the absolute value of the contact angle θ of water with respect to the sealant layer 20 20 are each preferably in the range of 90° to 120°. The absolute value of the contact angle θ of the release layer 10 10 and the absolute value of the contact angle θ of the sealant layer 20 20 are approximate, and the absolute value of the difference in the contact angle θ 10 , θ 20 |θ 10 - θ 20 | is 30° or less. In particular, the absolute value of the difference |θ 10 - θ 20 | is preferably 20° or less, more preferably 10° or less. The contact angle of water is an index of compatibility, and adherends with close contact angles tend to have high adhesiveness. Therefore, since the absolute value of the difference |θ 10 - θ 20 | is small, the adhesiveness is high, so that the sealant layer 20 can be prevented from falling off or floating during running, which is advantageous for the durability of the tire.

[0025] In the present invention, the contact angle θ of water 10 , θ 20It is measured in accordance with JIS R3257. For example, using a cut sample obtained by cutting out a product tire along the tire width direction, the contact angle θ of water in the release layer and the sealant layer on the cut sample 10 , θ 20 can be measured. Alternatively, it can also be measured by disassembling the inner surface of the tire and using a sheet sample processed into a sheet shape. Also, a sheet obtained by processing the sealant before applying it to the inner surface of the tire to a certain thickness, or a rubber sheet with a release agent used for the inner surface of the tire attached thereto may be used. Water is dropped onto each of the sample 51 of the release layer and the sample 52 of the sealant layer thus obtained, and the contact angle θ of the water droplet WD 10 , θ 20 can be measured respectively (see FIGS. 3(a) and (b)). In FIG. 3, the case where the contact angle θ 20 is larger than the contact angle θ 10 is illustrated, but the magnitude relationship between the contact angles θ 10 , θ 20 is not limited to this.

[0026] In the pneumatic tire described above, since both the release layer 10 and the sealant layer 20 contain a silicone-based composition, it contributes to improving the compatibility. Further, the absolute value of the difference between the contact angle θ 10 of water with respect to the release layer 10 and the contact angle θ 20 of water with respect to the sealant layer 20, |θ 10 - θ 20 | is set within a specific range (30° or less), so that the compatibility can be made very good. Thereby, the adhesiveness between the inner surface Ts of the tire and the sealant layer 20 can be enhanced, and the durability of the tire can be improved. Here, if the absolute value of the difference |θ 10 - θ 20 | exceeds 30°, since the release layer 10 and the sealant layer 20 are difficult to blend, the adhesiveness between the two decreases, and the durability of the tire tends to decrease.

[0027] In the above pneumatic tire, 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.

[0028] The above-described pneumatic tire can be manufactured by the following method. First, as described above, a pneumatic tire is manufactured that includes a tread portion 1, a pair of sidewall portions 2, and a pair of bead portions 3, and a release layer 10 containing a silicone-based composition is formed on the inner surface Ts of the tire. Here, the method of forming the release layer 10 on the inner surface Ts of the tire is not particularly limited. For example, it can be formed by applying a release agent to the inner surface of the green tire during vulcanization. Next, a sealant made of a silicone-based composition is applied to the inner surface Ts of the tire 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 inner surface Ts of the tire is set to 70°C or lower. If this temperature exceeds 70°C, the distortion generated in the pneumatic tire will increase in the process of applying the sealant to the inner surface Ts of the tire, and the durability of the tire will deteriorate. In particular, the temperature of the sealant when applying the sealant to the inner surface Ts of the tire 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, over-vulcanization of the rubber member is suppressed by the heating during the formation of the sealant layer 20. Also, since the release layer 10 and the sealant layer 20 contain similar materials, they are easily compatible with each other, and the sealant layer 20 can be well adhered to the inner surface Ts of the tire. In addition, since the sealant can be applied with the release agent adhering to the inner surface of the tire, there is no need to perform a process of removing the release agent by buffing or laser treatment, which also leads to an improvement in productivity.

[0029] FIG. 4 shows a specific manufacturing method of a pneumatic tire according to an embodiment of the present invention, and FIG. 5 shows a sealant layer formed on the inner surface of the tire in the tread portion. In FIG. 4, 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 inner surface Ts of the tire, the strip material 21 of the sealant can be spirally arranged on the release layer 10 while being inclined with respect to the tire circumferential direction Tc (see FIG. 5). 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] 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 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-component curable silicone are supplied from the pumps 32 and 33, respectively. Since the two-component curable silicone has a low viscosity immediately after the two liquids are mixed, it can be applied even at low temperatures.

[0031] 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 (e.g., 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 a first liquid and a second liquid in a combination where the curing reaction does not proceed, and are mixed at the time of use. Examples of 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 two-component curable silicone, for example, SST-2650 manufactured by Dow can be used.

[0032] 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 Sh 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 portion of the belt layer 7.

[0033] In the above-mentioned pneumatic tire, it is preferable that the thickness g (see Fig. 2) of the release layer 10 is in the range of 0.1 μm to 100.0 μm. By appropriately setting the thickness g of the release layer 10 in this way, the durability of the tire can be effectively improved. Here, if the thickness g of the release layer 10 is less than 0.1 μm, it becomes difficult to blend with the sealant layer 20, and the durability of the tire deteriorates. Conversely, if it is greater than 100.0 μm, when the tire is deformed and applied to the release layer 10, the deformation of the release layer 10 becomes significant, the destruction of the release layer 10 is promoted, and there is a risk that the sealant layer 20 will fall off. The thickness g of the release layer 10 is the average thickness. Such a thickness g of the release layer 10 can be detected, for example, using an electron microscope. When measuring the thickness g of the release layer 10 with an electron microscope, a cut sample obtained by cutting the 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) in the cut sample are measured, and the thickness g of the release layer 10 can be calculated by averaging the measured values measured at these plurality of locations.

[0034] Also, it is preferable that the thickness S (see Fig. 2) of the sealant layer 20 is in the range of 2.0 mm to 5.0 mm. Thereby, in addition to the shoulder portion Sh, 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, and conversely, if it is greater than 5.0 mm, the sealant layer 20 flows due to the centrifugal force of the tire, and the balance of the tire during running 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 by CT scan at 8 locations on the tire circumference, and measuring the thickness of the sealant layer 20 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 20e of the sealant layer 20, and the intermediate positions (both sides) between the tire equator position and the outer edge positions, in each of the photographed images, and calculating from the measured values at a total of 40 points.

[0035] In the above pneumatic tire, as shown in FIG. 2, at all positions of the belt layer 7 located at the innermost side in the tire radial direction, it is preferable that the distance (shortest distance) L from the belt layer 7 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 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 at that portion may become insufficient.

[0036] FIG. 6 shows a pneumatic tire according to another embodiment of the present invention. In FIG. 6, 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 closed cells 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

[0037] 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 release layer containing a silicone-based composition is provided on the inner surface of the tire, and a sealant layer is formed on the inner surface of the tire in the tread portion, and the contact angle θ 10 , θ 20 The tires of Comparative Example and Examples 1 to 7 were manufactured in which the absolute value of the difference, the type of sealant, the thickness g of the release layer, and the distance L were set as shown in Table 1.

[0038] Regarding these test tires, the durability and puncture sealing performance were evaluated by the following test methods, and the results are also shown in Table 1.

[0039] Durability: Each test tire was assembled onto a wheel with a rim size of 19×8.5J, and after conducting a running test on a drum tester under the conditions of an air pressure of 120 kPa, 100% of the maximum load, a running speed of 80 km, and a running distance of 6000 km, the state of the sealant layer was visually confirmed. The evaluation results were indicated as "◎(excellent)" when there was no lifting in the sealant layer and the sealant function could be exerted, "○(good)" when there was a slight lift in the sealant layer but the sealant function could be exerted, and "×(unacceptable)" when the sealant layer had peeled off.

[0040] Puncture sealing property: Each test tire was assembled onto a wheel with a rim size of 19×8.5J. Under the conditions of an initial air pressure of 250 kPa and a temperature of 23°C, a nail with a diameter of 5 mm was driven into the tread portion, and then the tire was left for two weeks with the nail removed, and the air pressure was measured. The evaluation results were indicated by an index with the reciprocal of the measured value, with the conventional example taken as 100. The larger this index value, the better the puncture sealing property.

[0041]

Table 1

[0042] As can be seen from Table 1, the pneumatic tires of Examples 1 to 7 had improved durability compared to the conventional example.

Explanation of symbols

[0043] 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 tire θ 10 ,θ 20 Contact angle of water

Claims

1. In a pneumatic tire comprising 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, it has a release layer containing a silicone-based composition on the inner surface of the tire, a sealant layer is formed on the inner side in the tire radial direction of the release layer in the tread portion, the sealant of the sealant layer is composed of a silicone-based composition, and the absolute value of the difference between the contact angle of water with respect to the release layer and the contact angle of water with respect to the sealant layer is 30° or less. A pneumatic tire characterized by this.

2. The pneumatic tire according to claim 1, wherein the thickness of the release layer is in the range of 0.1 μm to 100.0 μm.

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 silicone-based composition constituting the sealant is a two-component curable silicone.

5. 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.

6. 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.

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 less. A method for manufacturing a pneumatic tire characterized by this.

8. The method for manufacturing a pneumatic tire according to claim 7, 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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