Pneumatic tires

Abstract

To provide a pneumatic tire which makes it possible to exhibit good sealing property in spite of a temperature condition.SOLUTION: There is provided a pneumatic tire which is provided with a sealant layer 10 comprising an adhesiveness sealant material on the inner surface of a tread part 1. A thickness change ratio RG expressed by a following equation (1) is set to be 3% or less and a width change ratio RW expressed by a following equation (2) is set to be 3% or less, when defining the thickness of the sealant layer 10 at 0°C as G0, the thickness of the sealant layer 10 at 50°C as G50, the width of the sealant layer 10 at 0°C as W0, and the width of the sealant layer 10 at 50°C as W50. The equation of (1) is RG=(|G50-G0| / G0)×100, and the equation of (2) is RW=(|W50-W0| / W0)×100.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a self-sealing type pneumatic tire having a sealant layer on the inner surface of the tire. [Background technology]

[0002] It has been proposed to provide a sealant layer on the radially inner side of the inner liner layer in the tread portion of a pneumatic tire (see, for example, Patent Document 1). In such a pneumatic tire, when a foreign object such as a nail penetrates the tread portion, the sealant material constituting the sealant layer flows into the through hole, thereby suppressing the decrease in air pressure and enabling the tire to continue running.

[0003] In the above-mentioned self-sealing type pneumatic tire, if the viscosity of the sealant is low, the sealant can be expected to improve the sealing performance in that the sealant can easily flow into the through-holes, but if the sealant flows toward the tire center due to the influence of heat and centrifugal force applied during driving, and as a result, if the through-holes are out of the tire center region, there is a risk that the sealant will be insufficient and sufficient sealing performance will not be obtained. On the other hand, if the viscosity of the sealant is high, the above-mentioned flow of the sealant can be prevented, but the sealant will not easily flow into the through-holes, and there is a risk that the sealing performance will be reduced. Therefore, when providing a sealant layer on the inner surface of the tire, it is necessary to achieve a good balance between suppressing the flow of the sealant due to driving and ensuring good sealing performance.

[0004] In addition, since sealants are generally made mainly of rubber, their volume tends to change depending on temperature. That is, sealants tend to expand at high temperatures and shrink at low temperatures. In addition, since the viscosity of sealants also depends on temperature, their fluidity tends to change depending on temperature. That is, if the viscosity of the sealant decreases at high temperatures, the sealant may flow and the thickness and width of the sealant layer may vary. Due to such dimensional changes in the sealant layer, for example, if the thickness of the sealant layer decreases, it may become difficult for a sufficient amount of sealant to flow into the through holes, and if the width of the sealant layer decreases, the range in which the sealant layer can exhibit its sealing properties may become narrow. Tires may be used in various environments (cold regions, high temperature regions, regions with large daily ranges, regions with large annual ranges, etc.), and large temperature changes may occur depending on the running speed. Therefore, when providing a sealant layer in a tire, it is required to suppress dimensional changes in the sealant layer (sealant) caused by temperature changes and exhibit good sealing properties regardless of temperature conditions. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2006-152110 A Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a pneumatic tire having a sealant layer on the inner surface of the tire, which is capable of exhibiting good sealing properties regardless of temperature conditions. [Means for solving the problem]

[0007] The pneumatic tire of the present invention for achieving the above object includes a tread portion extending in a circumferential direction of the tire to form an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on the inner side of the sidewall portions in the outer radial direction of the tire, and the pneumatic tire has a sealant layer made of an adhesive sealant material provided on at least the inner surface of the tread portion, the adhesive sealant material being a rubber component 100 parts by mass Crosslinking agents containing sulfur components are used for 0.1 parts by mass ~ 40 parts by mass The thickness of the sealant layer at 0° C. is G0, and the thickness of the sealant layer at 50° C. is G 50 The width of the sealant layer at 0° C. is W0, the width of the sealant layer at 50° C. is W 50 Then, the thickness change rate R is expressed by the following formula (1): G is 3% or less, and the width change rate R W is 3% or less The viscosity η of the adhesive sealant material at 0°C 0 [Unit: kPa·s] and the viscosity η of the adhesive sealant material at 50°C 50 Ratio η to [unit: kPa s] 0 / η 50 is 6.0 or less, and in the adhesive sealant, a proportion A of the toluene insoluble matter represented by the following formula (3) is 30% by mass to 60% by mass. It is characterized by: R G =(|G 50 -G0| / G0)×100 (1) R W =(|W 50 -W0| / W0) × 100 (2) A = (M2 / M1) × 100 (3) (In the formula, M2 is the mass (unit: g) of the toluene insoluble matter remaining after the adhesive sealant material is immersed in toluene and left for one week, and M1 is the initial mass (unit: g) of the adhesive sealant material before it is immersed in toluene.) Effect of the Invention

[0008] The pneumatic tire of the present invention exhibits sealing properties by being provided with the sealant layer as described above. G and the width change rate R W Since the thickness is set sufficiently low, dimensional changes are unlikely to occur even when temperature changes occur, and excellent sealing properties can be exhibited regardless of temperature conditions.

[0009] In addition, the thickness change rate R G" is calculated using formula (1) above, but is specifically found by the following method. That is, at each of 12 equal parts around the inner circumference of the tire, three measurement points are taken: the tire equator and three points 10 mm inward in the tire width direction from each end of the sealant layer. At each measurement point, a needle with a diameter of 0.5 mm is inserted vertically into the sealant layer, and when the tip of the needle reaches the interface between the sealant layer and the inner surface of the tire, a mark is made at the position of the needle that corresponds to the surface of the sealant layer (the surface facing the tire cavity), and the length from the tip of the needle removed from the sealant layer to the aforementioned mark (sealant layer thickness) is measured. "Sealant layer thickness G0 at 0°C" and "sealant layer thickness G 50 The tire's surrounding temperature is set to each temperature condition (0℃ or 50℃) and left for one hour, after which the measurement is performed. 50 The difference (|G 50 -G0|), and the value at the measurement point where this difference is maximum is called the "thickness change rate R G Similarly, the width change rate R W " is calculated by the above formula (2), but specifically, it is obtained by the following method. That is, the inner circumference of the tire is divided into 12 equal parts, and each part is set as a measurement point, and the length between both ends of the sealant layer in the tire width direction (width of the sealant layer) is measured at each measurement point. "The width of the sealant layer at 0°C is W0" and "the width of the sealant layer at 50°C is W 50 The tire's surrounding temperature is set to each temperature condition (0℃ or 50℃) and left for 1 hour, after which the measurement is performed. W0 and W 50 The difference (|W 50 -W0|), and the value at the measurement point where this difference is maximum is called the "width change rate R W "

[0010] In the present invention, the viscosity η0 of the adhesive sealant at 0°C [unit: kPa·s] and the viscosity η 50 [Unit: kPa s] and the ratio η0 / η 50It is preferable that the viscosity is 6 or less. Setting the viscosity in this manner is advantageous for improving the sealing property. In particular, since the change in viscosity with temperature is appropriately small, excellent sealing property can be exhibited regardless of temperature conditions. The viscosity of the adhesive sealant material is a value measured using a rotational viscometer at the specified temperature conditions (0°C, 50°C) in accordance with JIS K6833-1:2008.

[0011] In the present invention, it is preferable that the adhesive sealant is crosslinked. By forming the sealant layer from a pre-crosslinked adhesive sealant in this manner, it is advantageous to prevent deformation of the sealant layer in the tire width direction and the tire circumferential direction.

[0012] In the present invention, the adhesive sealant preferably has a toluene-insoluble content ratio A of 30% to 60% by mass, as represented by the following formula (3). An adhesive sealant having such properties has a crosslink density in an appropriate range and exhibits small dimensional changes due to temperature changes, and is therefore advantageous in exhibiting excellent sealing properties regardless of temperature conditions. A = (M2 / M1) × 100 (3) (In the formula, M2 is the mass (unit: g) of the toluene insoluble matter remaining after the adhesive sealant material is immersed in toluene and left for one week, and M1 is the initial mass (unit: g) of the adhesive sealant material before it is immersed in toluene.)

[0013] In the present invention, a crosslinking agent is blended in the adhesive sealant material, and the crosslinking agent contains a sulfur component. nothing. This improves the adhesion of the adhesive sealant to the inner surface of the tire, which is advantageous in preventing deformation of the sealant layer in the tire width direction and tire circumferential direction (flow of the adhesive sealant).

[0014] In the present invention, it is preferable that the rubber component constituting the adhesive sealant contains butyl rubber. By blending butyl rubber in this manner, the adhesiveness of the adhesive sealant to the inner surface of the tire can be improved, which is advantageous for ensuring good sealing properties.

[0015] In the present invention, it is preferable to provide an auxiliary sheet that covers the surface of the sealant layer. By providing the auxiliary sheet in this manner, the deformation of the sealant layer is restricted by the auxiliary sheet, which is advantageous in suppressing the deformation and flow of the sealant layer. In addition, it is also possible to prevent foreign matter from adhering to the surface of the sealant layer.

[0016] In the following description, the tire dimensions are measured when the tire is mounted on a standard rim, inflated to the standard internal pressure, and loaded with the standard load. The "standard rim" is the rim that is determined for each tire by the standard system including the standard on which the tire is based, for example, the standard rim for JATMA, the "Design Rim" for TRA, or the "Measuring Rim" for ETRTO. The "standard internal pressure" is the air pressure that is determined for each tire by the standard system including the standard on which the tire is based, for example, the maximum air pressure for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "INFLATION PRESSURE" for ETRTO, but is 180 kPa when the tire is for a passenger car. "Normal load" refers to the load determined for each tire by each standard in the system of standards, including the standards on which the tire is based. In the case of JATMA, it is the maximum load capacity, in the case of TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and in the case of ETRTO, it is the "LOAD CAPACITY". However, if the tire is for passenger cars, it is a load equivalent to 88% of the above load. [Brief description of the drawings]

[0017] [Figure 1] 1 is a meridian cross-sectional view showing an example of a pneumatic tire of the present invention. [Diagram 2] FIG. 2 is a meridian cross-sectional view showing another example of a pneumatic tire of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The configuration of the present invention will be described in detail below with reference to the accompanying drawings.

[0019] As shown in FIG. 1, the pneumatic tire of the present invention (self-sealing type pneumatic tire) includes a tread portion 1 extending in the tire circumferential direction to form 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 tire radially inner side of the sidewall portions 2. In FIG. 1, the symbol CL indicates the tire equator. Although not depicted in FIG. 1 because it is a meridian cross section, the tread portion 1, the sidewall portions 2, and the bead portions 3 each extend in the tire circumferential direction to form an annular shape, thereby forming a toroidal basic structure of a pneumatic tire. In addition, other tire components in the meridian cross section also extend in the tire circumferential direction to form an annular shape unless otherwise specified.

[0020] In the example of Fig. 1, a carcass layer 4 is installed between a pair of left and right bead portions 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is folded back from the inside to the outside of the vehicle around the bead cores 5 and bead fillers 6 arranged in each bead portion 3. The bead fillers 6 are arranged on the outer peripheral side of the bead cores 5, and are enclosed by the main body and folded back portions of the carcass layer.

[0021] A plurality of belt layers 7 (two layers in FIG. 1) are embedded on the outer circumferential side of the carcass layer 4 in the tread portion 1. Of these belt layers 7, the layer with the smallest belt width is called the minimum belt layer 7a, and the layer with the largest belt width is called the maximum belt layer 7b. Each belt layer 7 includes a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and is arranged so that the reinforcing cords cross each other between layers. In these belt layers 7, the inclination angle of the reinforcing cords with respect to the tire circumferential direction is set to, for example, a range of 10° to 40°. A belt reinforcing layer 8 is provided on the outer circumferential side of the belt layer 7 in the tread portion 1. In the illustrated example, two belt reinforcing layers 8 are provided, which are a full cover layer that covers the entire width of the belt layer 7, and an edge cover layer that is further arranged on the outer circumferential side of the full cover layer and covers only the end portion of the belt layer 7. The belt reinforcing layer 8 includes organic fiber cords oriented in the tire circumferential direction, and the angle of the organic fiber cords with respect to the tire circumferential direction is set to, for example, 0° to 5°.

[0022] In the tread portion 1, a tread rubber layer R1 is disposed on the outer peripheral side of the above-mentioned tire constituent members (carcass layer 4, belt layer 7, belt reinforcing layer 8). The tread rubber layer R1 may have a structure in which two types of rubber layers (cap tread layer and under tread layer) with different physical properties are laminated in the tire radial direction. A side rubber layer R2 is disposed on the outer peripheral side (outside in the tire width direction) of the carcass layer 4 in the sidewall portion 2, and a rim cushion rubber layer R3 is disposed on the outer peripheral side (outside in the tire width direction) of the carcass layer 4 in the bead portion 3.

[0023] An inner liner layer 9 is provided on the inner surface of the tire along the carcass layer 4. This inner liner layer 9 is a layer for preventing air filled in the tire from permeating to the outside of the tire. The inner liner layer 9 is composed of, for example, a rubber composition mainly composed of butyl rubber having air permeation prevention properties. Alternatively, it can be composed of a resin layer having a thermoplastic resin as a matrix. In the case of a resin layer, an elastomer component may be dispersed in a thermoplastic resin matrix.

[0024] The present invention relates to a sealant layer 10, which is provided on the inner surface of such a pneumatic tire, as described below. Therefore, the basic structure of the pneumatic tire of the present invention is not limited to the above-mentioned structure as long as it has the sealant layer 10, which is described below. The sealant layer 10 is attached to the inner surface of a pneumatic tire having the above-mentioned basic structure. Specifically, the sealant layer 10 is provided in an area where a foreign object such as a nail may be stuck during driving, that is, on the inner surface of the tire (the tire radial inner side of the inner liner layer 9) corresponding to the ground contact area of ​​the tread portion 1. When a foreign object such as a nail is stuck in the tread portion 1, the sealant material constituting the sealant layer 10 flows into the through hole and seals the through hole, thereby suppressing the decrease in air pressure and enabling driving to be continued.

[0025] For the sealant layer 10 of the present invention, the thickness at 0° C. is G0, the thickness at 50° C. is G 50 In this case, the sealant layer 10 of the present invention has a thickness change rate R represented by the following formula (1): G The characteristic of G0 and G 50 The measurement points are the same, but the measurement temperatures are different, so in the figure, G0 and G 50 The thickness G is used as a symbol to indicate both of these. G Since is set sufficiently low, dimensional changes (changes in thickness) are unlikely to occur even when temperature changes occur, and a sufficient amount of sealant material can be ensured to flow into the through hole regardless of temperature conditions, thereby providing excellent sealing properties. R G =(|G 50 -G0| / G0)×100 (1)

[0026] At this time, the thickness change rate R GIf the thickness of the sealant layer 10 exceeds 3%, the amount of sealant material flowing into the through holes when the thickness of the sealant layer 10 is reduced cannot be sufficiently ensured, and good sealing properties cannot be maintained. The thickness of the sealant layer 10 is not particularly limited, but in a typical pneumatic tire, the thickness G of the sealant layer 10 is preferably, for example, 0.5 mm to 5.0 mm. The thickness of the sealant layer 10 described here is determined based on the above-mentioned G0 and G 50 This thickness is different from the thickness at room temperature (25°C). With this thickness, it is possible to suppress the flow of the sealant during running while ensuring good sealing properties. In addition, the processability when attaching the sealant layer 10 to the inner surface of the tire is also good. If the thickness of the sealant layer 10 is less than 0.5 mm, it is difficult to ensure sufficient sealing properties. If the thickness of the sealant layer 10 exceeds 5.0 mm, the tire weight increases and the rolling resistance deteriorates.

[0027] Furthermore, regarding the thickness of the sealant layer 10, the thickness at -30°C is -30 , thickness at 80℃ is G 80 In this case, the sealant layer 10 of the present invention has a thickness change rate R represented by the following formula (1′): G The thickness change rate R' is preferably 3% or less, and more preferably 2.5% or less. G If G' is set to be sufficiently small, dimensional changes (changes in thickness) are unlikely to occur even if significant temperature changes occur, and a sufficient amount of sealant material can be ensured to flow into the through hole regardless of temperature conditions, thereby achieving even better sealing properties. -30 , G 80 , R G ' changes only the temperature conditions to G0, G 50 , R G can be found in a similar manner. R G '=(|G 80 -G -30 | / G -30 )×100 (1')

[0028] Similarly, for the sealant layer 10 of the present invention, the width at 0° C. is W0, the width at 50° C. is W50 In this case, the sealant layer 10 of the present invention has a width change rate R represented by the following formula (2): W The characteristic is that W0 and W 50 The measurement points are the same, but the measurement temperatures are different, so in the figure, W0 and W 50 The thickness W is used as a symbol to indicate both of these. W Since is set sufficiently low, dimensional changes (changes in width) are unlikely to occur even when temperature changes occur, and an area that exhibits sealing properties can be sufficiently secured regardless of temperature conditions, thereby enabling excellent sealing properties to be exhibited. R W =(|W 50 -W0| / W0) × 100 (2)

[0029] At this time, the width change rate R W If the difference exceeds 3%, when the width of the sealant layer 10 is reduced, the area covered by the sealant layer 10 (area capable of exerting sealing properties) cannot be sufficiently secured, and good sealing properties cannot be maintained. The width of the sealant layer 10 is not particularly limited, but in a typical pneumatic tire, the width of the sealant layer 10 is preferably equal to or greater than the width Wb of the belt layer 7 (the width of the widest belt layer (maximum belt layer 7b in the illustrated example)). In addition, the protrusion amount w of the sealant layer 10 from the normal line of the carcass line passing through the widthwise end of the widest belt layer (maximum belt layer 7b in the illustrated example) is preferably within 20 mm. The width and protrusion amount w of the sealant layer 10 described here are determined based on the above-mentioned W0 and W 50 Unlike the above, these dimensions are at room temperature (25°C).

[0030] Furthermore, regarding the width of the sealant layer 10, the width at −30° C. is W -30 , the width at 80°C is W 80 In this case, the sealant layer 10 of the present invention has a width change rate R represented by the following formula (2'): W The width change rate R' is preferably 3% or less, and more preferably 2.5% or less. WIf W' is set to be sufficiently small, dimensional changes (changes in width) are unlikely to occur even if significant temperature changes occur, and a sufficient amount of sealant material can be ensured to flow into the through hole regardless of temperature conditions, thereby achieving even better sealing properties. -30 , W 80 , R W ' changes only the temperature conditions to W0, W 50 , W G can be found in a similar manner. R W '=(|W 80 -W -30 | / W -30 )×100 (2')

[0031] The sealant layer 10 can be formed by subsequently attaching an adhesive sealant (hereinafter simply referred to as "sealant") to the inner surface of a vulcanized pneumatic tire. For example, the sealant layer 10 can be formed by attaching a sealant molded into a sheet shape over the entire circumference of the inner surface of the tire, or by attaching a sealant molded into a string or strip shape in a spiral shape to the inner surface of the tire. In this case, it is preferable to use a cross-linked sealant. By using a sealant that has been cross-linked in advance in this way, deformation of the sealant in the tire width direction and tire circumferential direction can be more effectively prevented.

[0032] From the viewpoint of suppressing deformation of the sealant layer 10, as shown in FIG. 2, an auxiliary sheet 11 may be further provided on the surface of the sealant layer 10 (the surface exposed to the tire cavity) to cover the surface of the sealant layer 10. FIG. 2 has a structure common to FIG. 1 except for the auxiliary sheet 11. The presence of such an auxiliary sheet 11 restricts deformation of the sealant layer 10 (flow of the sealant material), which is advantageous in preventing deformation of the sealant material in the tire width direction and tire circumferential direction. In addition, the provision of the auxiliary sheet 11 can prevent foreign matter from adhering to the surface of the sealant layer 10. The material of the auxiliary sheet 11 is not particularly limited, but a resin film such as polyethylene or polyamide can be preferably used. Since the auxiliary sheet 11 mainly suppresses deformation of the sealant layer 10 as described above, it is not necessary for the auxiliary sheet 11 to be a sheet that covers the entire surface of the sealant layer 10, and it may be a material having holes or missing parts in a part such as a mesh or net shape. Furthermore, even when the auxiliary sheet 11 is in the form of a sheet having no holes or missing parts, it does not need to cover the entire surface of the sealant layer 10, and it is sufficient for it to cover at least 80%, and preferably 90% or more, of the surface area of ​​the sealant layer 10 (the area of ​​the surface exposed to the tire cavity).

[0033] In the present invention, the sealant may be a material that is generally used for the sealant layer 10 of a self-sealing type pneumatic tire. However, from the viewpoint of suppressing deformation of the sealant layer 10 due to temperature changes, the viscosity η0 at 0°C [unit: kPa·s] and the viscosity η at 50°C may be set to 0.05 to 0.55 kPa·s. 50 [Unit: kPa s] and the ratio η0 / η 50 Preferably, the viscosity ratio η0 / η1 is 6 or less, and more preferably 4 or less. Using a sealant material with such physical properties is advantageous in improving the sealing performance. In particular, since the change in viscosity with temperature change is small, excellent sealing performance can be achieved regardless of temperature conditions. In this case, the viscosity ratio η0 / η1 is 50 If the viscosity exceeds 6, the processability of the sealant may decrease. 50is not particularly limited, but from the viewpoint of the basic performance of the sealant material (the property of not easily flowing during driving while maintaining good sealing properties), the viscosity η0 should be set to, for example, 2 kPa·s to 100 kPa·s.

[0034] Furthermore, the viscosity of the sealant at -30°C is η -30 [Unit: kPa s], viscosity at 80℃ is η 80 The ratio η when [unit: kPa s] -30 / η 80 is preferably 18 or less, more preferably 12 or less. 80 For example, the viscosity η can be set to 0.5 kPa·s to 30 kPa·s. By setting the viscosity in this way, even if a significant temperature change occurs, the change in viscosity is appropriately small, so that excellent sealing properties can be exhibited regardless of the temperature conditions. -30 , η 80 The viscosity η0, η 50 can be found in a similar manner.

[0035] Furthermore, the sealant used in the present invention preferably has a property that the proportion A of the toluene insoluble matter represented by the following formula (3) is 30% by mass to 60% by mass, and preferably 35% by mass to 50% by mass. A = (M2 / M1) × 100 (3) (In the formula, M2 is the mass (unit: g) of the toluene insoluble matter remaining after the sealant was immersed in toluene and left for one week, and M1 is the initial mass (unit: g) of the sealant before it was immersed in toluene.)

[0036] A sealant material having such characteristics is effective in exhibiting excellent sealing properties regardless of temperature conditions. Specifically, by making the proportion A of the toluene insoluble matter 30% by mass to 60% by mass, the crosslink density can be improved, so that the material can be given a property of small dimensional change with temperature change, and excellent sealing properties can be exhibited regardless of temperature conditions. If the proportion A of the toluene insoluble matter is less than 30% by mass, the crosslink density is low, and the effect of suppressing dimensional change with temperature change cannot be sufficiently obtained. If the proportion A of the toluene insoluble matter exceeds 60% by mass, the crosslink density becomes too high, and there is a risk of the sealing properties being reduced.

[0037] The sealant used in the present invention is not particularly limited in terms of its specific composition as long as it has the above-mentioned characteristics. However, in order to reliably obtain the above-mentioned characteristics, it is preferable that the sealant used in the present invention is composed of a sealant composition having the composition described below.

[0038] In the sealant composition constituting the sealant of the present invention (hereinafter referred to as "sealant composition of the present invention"), the rubber component may contain a butyl-based rubber. The proportion of the butyl-based rubber in the rubber component is preferably 10% by mass or more, more preferably 20% by mass to 90% by mass. By containing the butyl-based rubber in this way, good adhesion to the inner surface of a tire can be ensured. If the proportion of the butyl-based rubber is less than 10% by mass, sufficient adhesion to the inner surface of a tire cannot be ensured.

[0039] In the sealant composition of the present invention, it is preferable to include halogenated butyl rubber as the butyl-based rubber. Examples of halogenated butyl rubber include chlorinated butyl rubber and brominated butyl rubber, and chlorinated butyl rubber can be particularly preferably used. When using chlorinated butyl rubber, the ratio of chlorinated butyl rubber to 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass to 85% by mass. By including halogenated butyl rubber (chlorinated butyl rubber), the reactivity of the rubber component with the crosslinking agent and organic peroxide described below is increased, which is advantageous for ensuring the sealing property and suppressing the flow of the sealant. In addition, the processability of the sealant composition can be improved. If the ratio of chlorinated butyl rubber is less than 5% by mass, the reactivity of the rubber component with the crosslinking agent and organic peroxide described below is not sufficiently improved, and the desired effect cannot be sufficiently obtained.

[0040] In the sealant composition of the present invention, the entire amount of the butyl-based rubber does not need to be halogenated butyl rubber (chlorinated butyl rubber), and non-halogenated butyl rubber can also be used in combination. Examples of non-halogenated butyl rubber include unmodified butyl rubbers that are usually used in sealant compositions, such as BUTYL-065 manufactured by JSR and BUTYL-301 manufactured by LANXESS. When halogenated butyl rubber and non-halogenated butyl rubber are used in combination, the amount of non-halogenated butyl rubber is preferably less than 20% by mass, more preferably less than 10% by mass, based on 100% by mass of the rubber component.

[0041] In the sealant composition of the present invention, it is preferable to use two or more kinds of rubbers in combination as the butyl-based rubber. That is, it is preferable to use chlorinated butyl rubber in combination with other halogenated butyl rubber (e.g., brominated butyl rubber) or non-halogenated butyl rubber. Since the three types of chlorinated butyl rubber, other halogenated butyl rubber (brominated butyl rubber), and non-halogenated butyl rubber have different vulcanization rates, when at least two types are used in combination, the physical properties (viscosity, elasticity, etc.) of the sealant composition after vulcanization are not uniform due to the difference in vulcanization rate. That is, due to the distribution (variation in concentration) of rubbers with different vulcanization rates in the sealant composition, relatively hard parts and relatively soft parts are mixed in the sealant layer after vulcanization. As a result, the flowability is suppressed in the relatively hard parts, and the sealing property is exhibited in the relatively soft parts, which is advantageous for achieving a good balance between these performances.

[0042] In the sealant composition of the present invention, other diene rubbers than butyl rubber can be blended as the rubber component. As the other diene rubbers, rubbers generally used in sealant compositions, such as natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), styrene isoprene butadiene rubber (SIBR), ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), and acrylonitrile butadiene rubber (NBR), can be used. These other diene rubbers can be used alone or as an arbitrary blend.

[0043] In the sealant composition of the present invention, it is preferable to add a crosslinking agent. The "crosslinking agent" in the present invention is a crosslinking agent other than organic peroxide, and examples thereof include sulfur, zinc oxide, cyclic sulfide, resin (resin vulcanization), and amine (amine vulcanization). As the crosslinking agent, it is preferable to use one containing a sulfur component (for example, sulfur). By adding a crosslinking agent in this way, it is possible to realize appropriate crosslinking for ensuring sealing properties and preventing the flow of the sealant. The amount of the crosslinking agent is preferably 0.1 to 40 parts by mass, more preferably 0.5 to 20 parts by mass, relative to 100 parts by mass of the above-mentioned rubber component. If the amount of the crosslinking agent is less than 0.1 part by mass, it is essentially the same as not containing the crosslinking agent, and appropriate crosslinking cannot be performed. If the amount of the crosslinking agent is more than 40 parts by mass, the crosslinking of the sealant composition proceeds too much, resulting in a decrease in sealing properties.

[0044] In the sealant composition of the present invention, it is preferable to use the above-mentioned crosslinking agent together with an organic peroxide, rather than using it alone. By blending the crosslinking agent and the organic peroxide together in this way, it is possible to realize an appropriate crosslinking for ensuring the sealing property and preventing the flow of the sealant. The blending amount of the organic peroxide is preferably 1 part by mass to 40 parts by mass, more preferably 1.0 part by mass to 20 parts by mass, relative to 100 parts by mass of the above-mentioned rubber component. If the blending amount of the organic peroxide is less than 1 part by mass, the amount of the organic peroxide is too small and crosslinking cannot be sufficiently performed, and desired physical properties cannot be obtained. If the blending amount of the organic peroxide exceeds 40 parts by mass, crosslinking of the sealant composition proceeds too much, resulting in a decrease in sealing property.

[0045] In using a crosslinking agent and an organic peroxide in combination, the mass ratio A / B of the amount of crosslinking agent A to the amount of organic peroxide B is preferably 5 / 1 to 1 / 200, more preferably 1 / 10 to 1 / 20. By using such a mixing ratio, it is possible to achieve a better balance between ensuring sealing properties and preventing flow of the sealant.

[0046] Examples of organic peroxides include dicumyl peroxide, t-butylcumyl peroxide, benzoyl peroxide, dibenzoyl peroxide, butyl hydroperoxide, p-chlorobenzoyl peroxide, and 1,1,3,3-tetramethylbutyl hydroperoxide. In particular, organic peroxides having a one-minute half-life temperature of 100°C to 200°C are preferred, and among the above-mentioned specific examples, dicumyl peroxide and t-butylcumyl peroxide are particularly preferred. In the present invention, the "one-minute half-life temperature" generally refers to the value described in NOF Corporation's "Organic Peroxide Catalog, 10th Edition." If not described, the value obtained from thermal decomposition in an organic solvent in the same manner as described in the catalog is used.

[0047] It is preferable to compound a crosslinking aid in the sealant composition of the present invention. The crosslinking aid is a compound that acts as a crosslinking reaction catalyst when compounded together with a crosslinking agent containing a sulfur component. By compounding a crosslinking agent and a crosslinking aid, the vulcanization speed can be increased, and the productivity of the sealant composition can be improved. The compounding amount of the crosslinking aid is preferably more than 0 part by mass and less than 1 part by mass, more preferably 0.1 part by mass to 0.9 parts by mass, relative to 100 parts by mass of the rubber component. By suppressing the compounding amount of the crosslinking aid in this way, it is possible to suppress the deterioration (thermal deterioration) of the sealant composition while promoting the crosslinking reaction as a catalyst. If the compounding amount of the crosslinking aid is 1 part by mass or more, the effect of suppressing thermal deterioration cannot be sufficiently obtained. Incidentally, since the crosslinking aid acts as a crosslinking reaction catalyst when compounded together with a crosslinking agent containing a sulfur component as described above, even if it is coexisted with an organic peroxide instead of the sulfur component, it does not act as a crosslinking reaction catalyst, and a large amount of the crosslinking aid must be used, which promotes thermal deterioration.

[0048] The amount of the crosslinking agent is preferably 50% by mass to 400% by mass, more preferably 100% by mass to 200% by mass, of the amount of the crosslinking aid described above. By blending the crosslinking agent and the crosslinking aid in a well-balanced manner, the crosslinking aid can exhibit its catalytic function well, which is advantageous for ensuring both sealing properties and preventing the sealant from flowing. If the amount of the crosslinking agent is less than 50% by mass of the amount of the crosslinking aid, the flowability decreases. If the amount of the crosslinking agent is more than 400% by mass of the amount of the crosslinking aid, the deterioration resistance decreases.

[0049] Examples of the crosslinking aid include sulfenamide-based, thiazole-based, thiuram-based, thiourea-based, guanidine-based, dithiocarbamate-based, aldehyde-amine-based, aldehyde-ammonia-based, imidazoline-based, and xanthogenic acid-based compounds (vulcanization accelerators). Among these, thiazole-based, thiuram-based, guanidine-based, and dithiocarbamate-based vulcanization accelerators can be preferably used. Examples of the thiazole-based vulcanization accelerators include 2-mercaptobenzothiazole and dibenzothiazyl disulfide. Examples of the thiuram-based vulcanization accelerators include tetramethylthiuram monosulfide and tetramethylthiuram disulfide. Examples of the guanidine-based vulcanization accelerators include diphenylguanidine and diorthotolylguanidine. Examples of the dithiocarbamate vulcanization accelerator include sodium dimethyldithiocarbamate, sodium diethyldithiocarbamate, etc. In particular, in the present invention, it is preferable to use a thiazole- or thiuram-based vulcanization accelerator, which can suppress variation in the performance of the resulting sealant composition.

[0050] In addition, a compound that actually functions as a crosslinking agent, such as quinone dioxime, may be conveniently called a crosslinking auxiliary, but since the crosslinking auxiliary in the present invention is a compound that functions as a catalyst for the crosslinking reaction by the crosslinking agent as described above, quinone dioxime does not correspond to the crosslinking auxiliary in the present invention.

[0051] The sealant composition of the present invention preferably contains a liquid polymer. By containing a liquid polymer in this way, the viscosity of the sealant composition can be increased, and the sealability can be improved. The amount of the liquid polymer is preferably 50 to 400 parts by mass, more preferably 70 to 200 parts by mass, based on 100 parts by mass of the rubber component. If the amount of the liquid polymer is less than 50 parts by mass, the effect of increasing the viscosity of the sealant composition may not be sufficiently obtained. If the amount of the liquid polymer is more than 400 parts by mass, the flow of the sealant cannot be sufficiently prevented.

[0052] The liquid polymer is preferably capable of co-crosslinking with the rubber component (butyl rubber) in the sealant material composition, and examples thereof include paraffin oil, polybutene oil, polyisoprene oil, polybutadiene oil, polyisobutene oil, aromatic oil, polypropylene glycol, etc. From the viewpoint of suppressing the temperature dependency of the physical properties of the sealant material composition to a low temperature and ensuring good sealing properties in a low temperature environment, paraffin oil, polybutene oil, polyisoprene oil, polybutadiene oil, aromatic oil, and polypropylene glycol are preferred, and paraffin oil is particularly preferred. By using paraffin oil, it is advantageous to set the viscosity for each of the above-mentioned temperatures to an appropriate range. In addition, the molecular weight of the liquid polymer is preferably 800 or more, more preferably 1000 or more, and even more preferably 1200 to 3000. By using a polymer with such a large molecular weight, it is possible to prevent the oil from migrating from the sealant layer provided on the inner surface of the tire to the tire body and affecting the tire.

[0053] The present invention will be further described below with reference to examples, but the scope of the present invention is not limited to these examples. EXAMPLES

[0054] In a pneumatic tire having a tire size of 235 / 40R18, a basic structure shown in FIG. 1 or FIG. 2, and a sealant layer on the inner surface of the tread portion, the thickness change rate RG , thickness change rate R G ', width change rate R W , width change rate R W ', viscosity η -30 , viscosity η0, viscosity η 50 , viscosity η 80 , the ratio η0 / η 50 , ratio η -30 / η 80 Tires of Comparative Examples 1 and 2 and Examples 1 to 8 were produced in which the ratio A of the toluene insoluble matter, the presence or absence of an auxiliary sheet, and the ratio of the area of ​​the auxiliary sheet to the surface area of ​​the sealant layer were set as shown in Table 1.

[0055] Thickness change rate R G is the thickness of the sealant layer at 0°C G0 and the thickness of the sealant layer at 50°C G 50 The thickness was calculated based on the following formula (1). Specifically, at each of 12 equal parts around the inner circumference of the tire, the measurement points were the tire equator and three points 10 mm inward in the tire width direction from each end of the sealant layer, and at each measurement point, a needle with a diameter of 0.5 mm was inserted vertically into the sealant layer, and when the tip of the needle reached the interface between the sealant layer and the inner surface of the tire, a mark was made at the position of the needle corresponding to the surface of the sealant layer (the surface on the tire inner cavity side), and the length from the tip of the needle removed from the sealant layer to the aforementioned mark (sealant layer thickness) was measured, and the "sealant layer thickness G0 at 0°C" and "sealant layer thickness G at 50°C" were calculated. 50 The tire's surrounding temperature is set to each temperature condition (0℃ or 50℃), and the tire is left for one hour. Then, the tire is measured and the G0 and G 50 The difference (|G 50 -G0|), and the value at the measurement point where this difference is maximum is called the "thickness change rate R G " R G =(|G 50 -G0| / G0)×100 (1)

[0056] Thickness change rate R G ' is the thickness of the sealant layer at -30℃ G -30 and the thickness of the sealant layer at 80°C G 80The thickness change rate R was calculated based on the following formula (1'). G It is common to: R G '=(|G 80 -G -30 | / G -30 )×100 (1')

[0057] Width change rate R W is the width of the sealant layer at 0°C W0 and the width of the sealant layer at 50°C W 50 Specifically, the inner circumference of the tire was divided into 12 equal parts, and the length between both ends of the sealant layer in the tire width direction (width of the sealant layer) was measured at each measurement point. The "width of the sealant layer at 0°C is W0" and the "width of the sealant layer at 50°C is W 50 The tire's surrounding temperature is set to each temperature condition (0℃ or 50℃), and the tire is left for one hour. Then, W0 and W 50 The difference (|W 50 -W0|), and the value at the measurement point where this difference is maximum is called the "width change rate R W " R W =(|W 50 -W0| / W0) × 100 (2)

[0058] Width change rate R W ' is the width W of the sealant layer at -30℃ -30 and the width W of the sealant layer at 80°C 80 The thickness change rate R was calculated based on the following formula (2'). W It is common to: R W '=(|W 80 -W -30 | / W -30 )×100 (2')

[0059] Viscosity η -30 is the viscosity of the sealant at -30℃, viscosity η0 is the viscosity of the sealant at 0℃, viscosity η 50is the viscosity of the sealant at 50℃, and viscosity η 80 is the viscosity of the sealant at 80°C, and was measured using a rotational viscometer under each temperature condition in accordance with JIS K6833-1:2008.

[0060] The proportion A (mass%) of the toluene insoluble matter was calculated from the mass M2 (unit: g) of the toluene insoluble matter remaining after the sealant was immersed in toluene and left for one week, and the initial mass M1 (unit: g) of the sealant before it was immersed in toluene, using the following formula (3). A = (M2 / M1) × 100 (3)

[0061] In all the examples, the width of the belt layer was 195 mm, the width of the sealant layer (width at 25° C.) was 215 mm (1.10% of the width of the belt layer), and the thickness of the sealant layer (thickness at 25° C.) was 3 mm.

[0062] The test tires were evaluated for extrusion speed, processability, and sealability by the following test methods. The results are shown in Table 1.

[0063] Sealing ability After each test tire was left to stand for 24 hours under the temperature conditions described below, it was mounted on a wheel with a rim size of 18 x 8.5J and mounted on a test vehicle, and a nail with a diameter of 4.0 mm was driven into the tread part under conditions of an initial air pressure of 250 kPa and a load of 8.5 kN. Furthermore, the tire was left to stand for 1 hour under the temperature conditions described below, and the air pressure was measured after the nail was removed. The temperature conditions were -30°C, 0°C, 50°C, and 80°C, and tests were performed under each temperature condition. The temperature conditions when the nail was driven in were the same as those when the tire was left to stand before and after the nail was driven in. The evaluation results were shown in the following four stages. If the evaluation result was "○" or "◎", it means that sufficient sealing properties were exhibited, and if it was "◎", it means that particularly excellent sealing properties were exhibited. ◎: Air pressure after standing is 240kPa or more and 250kPa or less ○: Air pressure after standing is 230kPa or more and less than 240kPa △: Air pressure after standing is 200kPa or more and less than 230kPa ×: Air pressure after standing is less than 200 kPa

[0064] Sealant fluidity The test tire was mounted on a wheel with a rim size of 18 x 8.5J and attached to a drum testing machine, and the tire was driven for one hour at an air pressure of 220kPa, a load of 8.5kN, and a speed of 150km / h, and the sealant flow state after the run was examined. The evaluation results were evaluated by drawing 20 x 40 5mm squares on the surface of the sealant layer before the run, and counting the number of squares whose shape was distorted after the run. If no sealant flow was observed (0 distorted squares), it was indicated with a "○", if the number of distorted squares was less than 1 / 4 of the total, it was indicated with a "△", and if the number of distorted squares was 1 / 4 or more of the total, it was indicated with an "X".

[0065] [Table 1]

[0066] As is clear from Table 1, the pneumatic tires of Examples 1 to 8 exhibited excellent sealing properties regardless of temperature conditions. The pneumatic tires of Examples 1 to 8 also had good fluidity, and the flow of the sealant was suppressed after driving. In particular, in the tires of Examples 1 to 5 equipped with the auxiliary sheet, no flow of the sealant was observed at all, and the fluidity was particularly excellent. On the other hand, in Comparative Examples 1 and 2, the thickness change rate R G and the width change rate R W As a result, sufficient sealing and fluidity could not be ensured. [Explanation of symbols]

[0067] 1 Tread section 2 Sidewall 3 Bead section 4 Carcass layer 5 Bead Core 6 Bead Filler 7 Belt layer 8 Belt reinforcement layer 9 Inner liner layer 10 Sealant Layer 11 Booster seat R1 Tread rubber layer R2 Side rubber layer R3 rim cushion rubber layer CL Tire Equator

Claims

1. A pneumatic tire comprising a tread portion extending in a circumferential direction of the tire to form an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on the inner side of the sidewall portions in the outer radial direction of the tire, and a sealant layer made of an adhesive sealant material is provided on at least the inner surface of the tread portion, The adhesive sealant is made of a sealant composition in which 0.1 to 40 parts by mass of a crosslinking agent containing a sulfur component is blended with respect to 100 parts by mass of a rubber component, The thickness of the sealant layer at 0° C. is G 0 The thickness of the sealant layer at 50° C. is G 50 The width of the sealant layer at 0° C. is W 0 The width of the sealant layer at 50° C. is W 50 Then, the thickness change rate R is expressed by the following formula (1): G is 3% or less, and the width change rate R W a ratio η 0 / η 50 of a viscosity η 0 (unit: kPa·s) of the adhesive sealant at 0°C to a viscosity η 50 (unit: kPa·s) of the adhesive sealant at 50°C is 6.0 or less, and a proportion A of a toluene-insoluble matter in the adhesive sealant, as represented by the following formula (3), is 30 to 60 mass%: R G =(|G 50 -G 0 | / G 0 )×100 (1) R W =(|W 50 -W 0 | / W 0 )×100 (2) A=(M2 / M1)×100 (3) (In the formula, M2 is the mass (unit: g) of the toluene insoluble matter remaining after the adhesive sealant material is immersed in toluene and left to stand for one week, and M1 is the initial mass (unit: g) of the adhesive sealant material before it is immersed in toluene.)

2. 2. The pneumatic tire of claim 1, wherein the adhesive sealant material is crosslinked.

3. 3. The pneumatic tire according to claim 1, wherein a rubber component constituting the adhesive sealant material contains butyl rubber.

4. 4. The pneumatic tire according to claim 1, further comprising an auxiliary sheet for covering a surface of the sealant layer.

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