Sealant material composition and pneumatic tires

Abstract

A sealing material composition forming a sealant layer disposed on an inner surface of a pneumatic tire, the sealing material composition comprising: 1 part to 40 parts by mass of an organic peroxide; 0.1 parts by mass to 40 parts by mass of a crosslinking agent blended per 100 parts by mass of a rubber component comprising a chlorinated butyl rubber; and another halogenated butyl rubber besides the chlorinated butyl rubber.

Description

Technical field

[0001] The present invention relates to a sealant material composition forming a sealant layer of a self-sealing pneumatic tire, which includes the sealant layer in a tire inner surface. State of the art

[0002] In a known pneumatic tire, a sealant layer is provided on an inner side in the tire radial direction of an inner liner layer in a tread portion (see, for example, Patent Document 1). In such a pneumatic tire, when a foreign object such as a nail or the like penetrates the tread portion, the sealant flows into the through hole, thereby suppressing a reduction in air pressure and allowing travel to continue.

[0003] In the self-sealing pneumatic tire described above, when the viscosity of the sealant is low, an improvement in sealing properties can be expected because the sealant easily flows into the through-hole. However, when the sealant flows toward a tire center side due to the effects of heat and centrifugal force exerted during driving, and as a result, the through-hole deviates from a tire center region, there is a risk that there is insufficient sealant and sealing properties cannot be sufficiently achieved. On the other hand, when the viscosity of the sealant is high, the above-described flow of the sealant can be prevented, but the sealant does not easily flow into the through-hole, and there is a risk that the sealing properties will deteriorate.Thus, it is difficult to ensure good sealing properties while suppressing flow of the sealant during driving, and there is a need for a measure to provide these performances in a well-balanced, compatible manner by improving the physical properties of the sealant material composition constituting the sealant layer. DE 11 2019 001 400 T5 also discloses a sealant composition for pneumatic tires.

[0004] Patent Document 1: JP 2006-152110 A Brief description of the inventionTechnical problem

[0005] An object of the present invention is to provide a sealant material composition which makes it possible to ensure good sealing properties and to suppress driving-induced sealant flow. Solution to the problem

[0006] The sealant material composition according to one embodiment of the present invention, which achieves the above-described object, is a sealant material composition according to claim 1. Preferred embodiments are defined in subclaims 2 to 8. Furthermore, the present invention also provides a pneumatic tire according to claim 9. Advantageous effects of the invention

[0007] Since the sealant material composition according to one embodiment of the present invention has the above-described mixture, when the sealant material composition is used in a sealant layer for a pneumatic tire, travel-induced sealant flow can be suppressed while ensuring good sealing properties. Specifically, by containing the chlorinated butyl rubber and performing crosslinking using a combination of the crosslinking agent and the organic peroxide, sufficient elasticity that does not cause flow during travel can be achieved while ensuring a viscosity sufficient to obtain good sealing properties, and these properties can be provided in a well-balanced, compatible manner.

[0008] The rubber component contains, in addition to the chlorinated butyl rubber, another halogenated butyl rubber. By using the combination of the chlorinated butyl rubber and another halogenated butyl rubber as described above, the different vulcanization rates of these rubbers depending on the position of the sealant composition (sealant layer) after vulcanization result in differences in physical properties such as viscosity and elasticity, which is advantageous for providing good sealing properties and adequate flowability in a well-balanced, compatible manner.

[0009] In one embodiment of the present invention, the crosslinking agent preferably includes a sulfur component. This increases the reactivity of the rubber component (halogenated butyl rubber) with the crosslinking agent (sulfur) and the organic peroxide, and the sealant material composition can provide better processability.

[0010] In one embodiment of the present invention, 50 to 400 parts by mass of a liquid polymer are preferably blended per 100 parts by mass of the rubber component. The liquid polymer is preferably paraffin oil. Furthermore, the molecular weight of the paraffin oil is preferably 800 or more. Accordingly, a sufficiently high viscosity can be imparted to the rubber component, which is advantageous for improving sealing properties.

[0011] In one embodiment of the present invention, a crosslinking aid is preferably included. The crosslinking aid is preferably a thiazole-based compound or a thiuram-based compound. Furthermore, the blended amount of the crosslinking aid is preferably 50% to 400% by mass of the blended amount of the crosslinking agent. This can increase the vulcanization rate, which can improve productivity.

[0012] In a pneumatic tire including the sealant layer formed from the sealant material composition according to an embodiment of the present invention described above, the assurance of sealing properties and the suppression of sealant flow can be provided in a well-balanced, compatible manner by excellent physical properties of the sealant material composition described above. Brief description of the drawings Fig. 1 is a meridian cross-sectional view illustrating a self-sealing type pneumatic tire according to an embodiment of the present invention. Description of embodiments

[0013] Configurations of embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0014] A rubber component in a sealant material composition according to one embodiment of the present invention always contains a halogenated butyl rubber. As the halogenated rubber, a chlorinated butyl rubber is always included, and another halogenated butyl rubber, such as a brominated butyl rubber, is additionally used in combination. The proportion of the halogenated butyl rubber in the rubber component is preferably 10 mass% or more, more preferably 20 mass% or more, and even more preferably 40 mass% or more. Furthermore, the proportion of the halogenated butyl rubber in the rubber component is preferably 100 mass%, more preferably 100 mass% or less, and even more preferably 90 mass% or less.The reactivity of the rubber component and a crosslinking agent or an organic peroxide as described below is increased by using the halogenated butyl rubber (chlorinated butyl rubber) as described above, and this is advantageous in ensuring sealing properties and suppressing flow of the sealant in a compatible manner. Furthermore, the processability of the sealant composition can also be improved. A halogenated butyl rubber commonly used in sealant compositions can be used.

[0015] The proportion of the chlorinated butyl rubber in the halogenated butyl rubber is preferably 1% by mass or more, and more preferably 10% by mass or more. If the proportion of the chlorinated butyl rubber is less than 1% by mass, the reactivity of the rubber component and the crosslinking agent or organic peroxide described below will not improve sufficiently, and a desired effect cannot be sufficiently achieved.

[0016] In the sealant material composition of one embodiment of the present invention, not all of the rubber component needs to be the halogenated butyl rubber, and non-halogenated butyl rubber may also be used in combination. Examples of the non-halogenated butyl rubber include unmodified butyl rubber normally used in a sealant material composition, such as BUTYL-065 available from JSR Corporation and BUTYL-301 available from LANXESS AG. In a case where the halogenated butyl rubber and the non-halogenated butyl rubber are used in combination, a blended amount of the non-halogenated butyl rubber may preferably be less than 20 mass%, and more preferably less than 10 mass%, per 100 mass% of the rubber component.

[0017] In the sealing material composition of one embodiment of the present invention, two or more types of rubber are preferably used in combination. That is, another type of halogenated butyl rubber (for example, brominated butyl rubber) or the non-halogenated butyl rubber is preferably used in combination with the chlorinated butyl rubber. The three types, namely the chlorinated butyl rubber, another type of halogenated butyl rubber, and the non-halogenated butyl rubber, differ from each other in vulcanization rate, and thus, when at least the two types are used in combination, differences in physical properties such as viscosity and elasticity occur after vulcanization depending on the position of the resulting sealant composition (sealant layer) due to these differences in vulcanization rates.This is advantageous in that it suppresses flow in the relatively hard portion while providing sealing properties in the relatively soft portion, providing these properties in a well-balanced, compatible manner. Note that when a non-halogenated butyl rubber is included, the proportion of the butyl rubber (halogenated butyl rubber and non-halogenated butyl rubber) in the rubber component is preferably 10 mass % or more, and more preferably 20 mass % or more. Furthermore, the proportion of the butyl rubber (halogenated butyl rubber and non-halogenated butyl rubber) in the rubber component is preferably 100 mass % or less, and more preferably 90 mass % or less.

[0018] In the sealing material composition of one embodiment of the present invention, in addition to the above-described butyl rubber (halogenated butyl rubber and non-halogenated butyl rubber), other diene rubbers may also be blended as a rubber component. As the other diene rubber, rubbers generally used in a sealing material composition, 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), may be used. Other diene rubbers may be used alone or as an arbitrary blend.

[0019] The sealant material composition according to one embodiment of the present invention always contains a crosslinking agent and an organic peroxide. Note that "crosslinking agent" in one embodiment of the present invention refers to a crosslinking agent other than an organic peroxide, and examples of the crosslinking agent include sulfur, sphalerite, cyclic sulfide, a resin (resin vulcanization), amine (amine vulcanization), and quinone dioxime. As the crosslinking agent, it is preferable to use a crosslinking agent including a sulfur component (e.g., sulfur). By using and blending the crosslinking agent and the organic peroxide in combination, sufficient crosslinking to ensure sealing properties and prevent flow of the sealant can be realized in a compatible manner.The blended amount of the crosslinking agent is 0.1 part by mass to 40 parts by mass, preferably 0.5 parts by mass to 10 parts by mass, per 100 parts by mass of the above-described rubber component. In addition, the blended amount of the organic peroxide is 1 part by mass to 40 parts by mass, and preferably 5 parts by mass to 20 parts by mass, per 100 parts by mass of the above-described rubber component. When the blended amount of the crosslinking agent is less than 0.1 part by mass, the blended amount of the crosslinking agent is the same as the blended amount when substantially no crosslinking agent is contained, and proper crosslinking cannot be performed. When the blended amount of the crosslinking agent exceeds 40 parts by mass, the crosslinking of the sealant material composition proceeds excessively rapidly, and the sealing properties deteriorate.The case where the blended amount of organic peroxide is less than 1 part by mass corresponds to the case where essentially no organic peroxide is contained, and thus proper crosslinking cannot be performed. If the blended amount of organic peroxide exceeds 40 parts by mass, the crosslinking of the sealant material composition will proceed excessively, and the sealing properties will deteriorate.

[0020] When the crosslinking agent and the organic peroxide are used in combination in this way, the ratio A / B of the crosslinking agent blending amount A to the organic peroxide blending amount B can preferably be set to 5 / 1 to 1 / 200, and more preferably to 1 / 10 to 1 / 20. According to such a blending ratio, ensuring sealing properties and preventing sealant flow can be achieved in a more balanced, compatible manner.

[0021] Examples of the organic peroxide include dicumyl peroxide, t-butylcumyl peroxide, benzoyl peroxide, dibenzoyl peroxide, butyl hydroperoxide, p-chlorobenzoyl peroxide, and 1,1,3,3-tetramethylbutyl hydroperoxide. In particular, an organic peroxide having a one-minute half-life temperature of 100°C to 200°C is preferable, and among the specific examples described above, dicumyl peroxide and t-butylcumyl peroxide are particularly preferable. Note that in one embodiment of the present invention, a value described in the "Catalog of Organic Peroxides 10th Edition" by Nippon Oil & Fats Co., Ltd. is generally used as the "one-minute half-life temperature." In a case where a value is not described, a value determined from thermal decomposition in an organic solvent by a method identical to a method described in the catalog is used.

[0022] The sealant material composition of one embodiment of the present invention can be blended with a liquid polymer. By blending the liquid polymer, the viscosity of the sealant material composition can be improved, and the sealing properties can be enhanced. The blended amount of the liquid polymer is preferably 50 parts by mass to 400 parts by mass, and more preferably 70 parts by mass to 200 parts by mass, per 100 parts by mass of the above-described rubber component. If the blended amount of the liquid polymer is less than 50 parts by mass, the effect of improving the viscosity of the sealant material composition cannot be sufficiently achieved. If the blended amount of the liquid polymer exceeds 400 parts by mass, sealant flow cannot be sufficiently prevented.

[0023] The liquid polymer is preferably co-crosslinkable with the rubber component (butyl rubber) in the sealant material composition, and examples of the liquid polymer include aromatic oil, polybutene oil, paraffin oil, polyisoprene oil, polybutadiene oil, and polyisobutene oil. Among them, from the viewpoint of reducing the temperature dependence of the physical properties of the sealant material composition as much as possible, the use of paraffin oil is preferred. When paraffin oil is used, the molecular weight is preferably 800 or more, more preferably 1000 or more, and even more preferably 1200 or more and 3000 or less. By using the high-molecular-weight liquid polymer, displacement of an oil component from the sealant layer provided in the tire inner surface to a tire main body can be prevented from affecting the tire.

[0024] The sealing material composition of one embodiment of the present invention may be blended with a crosslinking aid (vulcanization accelerator). Crosslinking aid refers to a compound that acts as a crosslinking reaction catalyst by blending the compound with the crosslinking agent including the sulfur component. By blending the crosslinking agent and the crosslinking aid, the vulcanization rate can be increased and the production properties of the sealing material composition can be improved. The blended amount of the crosslinking aid (vulcanization accelerator) is more than 0 parts by mass and less than 1 part by mass, preferably 0.1 part by mass to 0.9 part by mass, per 100 parts by mass of the above-described rubber component.By thus reducing the blended amount of the crosslinking aid, the decomposition (heat decomposition) of the sealant material composition can be suppressed while promoting the effect as a crosslinking reaction catalyst. If the blended amount of the crosslinking aid is 1 part by mass or more, the effect of suppressing heat decomposition cannot be sufficiently achieved. It should be noted that the crosslinking aid is a crosslinking aid that acts as a crosslinking reaction catalyst by mixing the crosslinking aid with the crosslinking agent including the sulfur component as described above. Therefore, if the crosslinking aid coexists with an organic peroxide instead of the sulfur component, the effect as a crosslinking reaction catalyst cannot be achieved, the crosslinking aid must be used in large amounts, and heat decomposition will be promoted.

[0025] The blended amount of the crosslinking aid is preferably 50 mass % to 400 mass % and more preferably 100 mass % to 200 mass % of the blended amount of the crosslinking agent described above. By appropriately blending the crosslinking aid with the crosslinking agent as described above, a good catalytic function of the crosslinking aid can be achieved, which is advantageous in that ensuring sealing properties and preventing sealant flow are provided in a compatible manner. If the blended amount of the crosslinking aid is less than 50 mass % of the blended amount of the crosslinking agent, flowability decreases. If the blended amount of the crosslinking aid exceeds 400 mass % of the blended amount of the crosslinking agent, aging resistance performance decreases.

[0026] 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 xanthogen-based compounds (vulcanization accelerators). Of these, thiazole-based, thiuram-based, guanidine-based, and dithiocarbamate-based vulcanization accelerators can be suitably used. Examples of the thiazole-based vulcanization accelerator include 2-mercaptobenzothiazole and dibenzothiazyl disulfide. Examples of the thiuram-based vulcanization accelerator include tetramethylthiuram monosulfide and tetramethylthiuram disulfide. Examples of the guanidine-based vulcanization accelerator include diphenylguanidine and di-ortho-tolylguanidine. Examples of the dithiocarbamate-based vulcanization accelerator include sodium dimethyldithiocarbamate and sodium diethyldithiocarbamate.In particular, in one embodiment of the present invention, thiazole-based or thiuram-based vulcanization accelerators are used, which can suppress fluctuations in the performance of the resulting sealant material composition. Among the thiuram-based vulcanization accelerators, tetramethylthiuram disulfide is particularly suitable due to its high vulcanization accelerating effect.

[0027] It should be noted that, for example, a compound such as quinone dioxime, which actually functions as the crosslinking agent, may be referred to as a crosslinking aid for convenience, but the crosslinking aid in one embodiment of the present invention is a compound that functions as a catalyst of the crosslinking reaction using the crosslinking agent as described above, and thus the quinone dioxime does not correspond to the crosslinking aid in one embodiment of the present invention.

[0028] Since the sealant composition according to one embodiment of the present invention contains at least the chlorinated butyl rubber, while imparting a sufficiently high viscosity to the rubber component, by performing crosslinking using a combination of the crosslinking agent and the organic peroxide, sufficient elasticity is achieved that does not cause running-induced flow, while ensuring a viscosity sufficient to obtain good sealing properties, which properties can be provided in a well-balanced, compatible manner. Thus, when the sealant composition is applied to the sealant layer of the self-sealing type pneumatic tire described below, excellent sealing properties can be exhibited without causing running-induced flow of the sealant layer.

[0029] As in Fig. 1, the pneumatic tire according to an embodiment of the present invention includes a tread portion 1 extending in the tire circumferential direction having an annular shape, a pair of sidewall portions 2 arranged on both sides of the tread portion 1, and a pair of bead portions 3 arranged on an inner side of the sidewall portions 2 in the tire radial direction. Note that "CL" in Fig. 1 denotes a tire equator. It should be noted that Fig.1 is a meridian cross-sectional view, and although not illustrated, the tread portion 1, the sidewall portions 2, and the bead portions 3 each extend in the tire circumferential direction and each have an annular shape, thus forming an annular basic structure of the pneumatic tire. Other tire components in the meridian cross-sectional view also extend in the tire circumferential direction to form annular shapes unless otherwise stated.

[0030] In the example of Fig.1, a carcass layer 4 is mounted between the 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 a vehicle inner side to a vehicle outer side around a bead core 5 and a bead filler 6 disposed in each of the bead portions 3. Furthermore, the bead filler 6 is disposed on an outer peripheral side of the bead core 5, and the bead filler 6 is enclosed by a body portion and a folded-back portion of the carcass layer 4.

[0031] A plurality of belt layers 7 (two layers in Fig.1) are embedded on an outer peripheral side of the carcass layer 4 in the tread portion 1. Of the plurality of belt layers 7, a layer having the smallest belt width is referred to as a minimum belt layer 7a, and a layer having the largest belt width is referred to as a maximum belt layer 7b. The belt layers 7 each include a plurality of reinforcing cords inclined with respect to the tire circumferential direction and are arranged so that the reinforcing cords of the different plies intersect each other. In these belt layers 7, the inclination angle of the reinforcing cords with respect to the tire circumferential direction is set in a range of, for example, 10° or more and 40° or less. A belt reinforcing layer 8 is provided on an outer peripheral side of the belt layers 7 in the tread portion 1.In the illustrated example, the belt reinforcing layer 8 is provided with two layers: a full cover layer covering the entire width of the belt layer 7, and an edge cover layer disposed further outward on the outer peripheral side than the full cover layer and covering only an end portion of the belt layer 7. The belt reinforcing layer 8 includes an organic fiber cord oriented in the tire circumferential direction, and an angle of the organic fiber cord with respect to the tire circumferential direction is set to, for example, 0° to 5°.

[0032] On the tire inner surface, along the carcass layer 4, there is an inner liner layer 9. The inner liner layer 9 is a layer that prevents air from leaking out of the tire. The inner liner layer 9 includes, for example, a rubber composition containing butyl rubber with air permeation prevention performance as a main component. Alternatively, the inner liner 9 may also include a plastic layer containing a thermoplastic resin as a matrix. In the case of the plastic layer, a plastic layer including an elastomer component dispersed in a thermoplastic resin matrix may be used.

[0033] As in Fig.As illustrated in FIG. 1, a sealant layer 10 is provided on an inner side in the tire radial direction of the inner liner layer 9 in the tread portion 1. A sealant material composition according to an embodiment of the present invention is used in the sealant layer 10. The sealant layer 10 is attached to the inner surface of a pneumatic tire having the basic structure described above. When, for example, a foreign matter such as a nail or the like penetrates into the tread portion 1, the sealant material constituting the sealant layer 10 flows into the through hole, thereby suppressing a reduction in air pressure and allowing travel to continue.

[0034] For example, the sealant layer 10 has a thickness of 0.5 mm to 5.0 mm. Since the sealant layer 10 has this thickness, flow of the sealant during driving can be suppressed while ensuring good sealing properties. In addition, good workability is achieved when applying the sealant layer 10 to the tire inner surface. If the thickness of the sealant layer 10 is less than 0.5 mm, it becomes difficult to ensure sufficient sealing properties. If the thickness of the sealant layer 10 is more than 5.0 mm, the tire weight increases and the rolling resistance decreases. Note that the thickness of the sealant layer 10 refers to the average thickness.

[0035] The sealant layer 10 can be formed by subsequently adhering the sealant layer 10 to the inner surface of the vulcanized pneumatic tire. For example, the sealant layer 10 can be formed by adhering a sealant material including the sealant material composition described below and formed in a sheet shape to the entire circumference of the tire inner surface, or by spirally adhering a sealant material including the sealant material composition described below and formed in a strand-like shape or a strip-like shape to the tire inner surface. Furthermore, the sealant material composition is heated at this time, so that fluctuations in the performance of the sealant material composition can be suppressed.As the heating condition, a temperature of preferably 140°C to 180°C, and more preferably 160°C to 180°C, and a heating time of preferably 5 minutes to 30 minutes, and more preferably 10 minutes to 20 minutes can be selected. According to the method for manufacturing a pneumatic tire, a pneumatic tire can be efficiently manufactured that has excellent puncture sealing properties and is not prone to sealant flow.

[0036] The sealant layer 10 is provided on the tire inner surface corresponding to a region where a foreign object such as a nail may penetrate during running, that is, a ground contact region of the tread portion 1. With the sealant layer 10 provided in a wide area on the tire inner surface as described above, flow of the sealant is particularly likely to occur in an end portion in the tire width direction; in addition, however, flow may occur in the entire region in the tire width direction. On the other hand, since the sealant material composition according to an embodiment of the present invention provides sealing properties and flow properties in a well-balanced, highly compatible manner through the above-described blend, flow, particularly flow of the sealant as a whole, can be effectively suppressed during high-speed running.

[0037] The present invention will be described below using working examples, but the scope of the present invention is not limited to the examples. Examples

[0038] Tires were manufactured according to Comparative Examples 1 to 7 and Examples 1 to 36. The tires have a tire size of 255 / 40R20, include the Fig. 1 and include a sealant layer formed of a sealant on an inner side in the tire radial direction of an inner liner layer in a tread portion. The composition of the sealant material composition constituting the sealant layer was determined as shown in Tables 1 to 4.

[0039] For these test tires, the sealing properties (initial performance and after heat decomposition acceleration treatment) and the flowability of the sealant were evaluated by the following test methods, and the results are shown in Tables 1 to 4. Sealing properties (initial performance)

[0040] The test tires were mounted on 20×9J wheels and mounted on a test vehicle with an initial air pressure of 250 kPa and a load of 8.5 kN. A 4 mm diameter nail was driven into the tread portion, and then the test tire was left standing with the nail removed for one hour. The air pressure was then measured. The evaluation results are presented in the following five stages. 5: The air pressure after standing was at least 240 kPa and 250 kPa or less. 4: The air pressure after standing was at least 230 kPa and less than 240 kPa. 3: The air pressure after standing was at least 220 kPa and less than 230 kPa 2: The air pressure after standing was at least 200 kPa and less than 220 kPa 1: The air pressure after standing was less than 200 kPa Sealing properties (after heat decomposition acceleration treatment)

[0041] The test tires were mounted on wheels with a rim size of 20×9J and mounted on a test vehicle. The heat decomposition acceleration treatment was conducted by leaving the test tires in a state where the test tires were filled with oxygen at an air pressure of 220 kPa and 70°C for 30 days. A 4 mm diameter nail was driven into the tread portion of the test tires after the heat decomposition acceleration treatment with an initial air pressure of 250 kPa and a load of 8.5 kN. Afterward, the tire was left in a state with the nail removed for one hour. The air pressure was then measured. The evaluation results are given in the following five stages. 5: The air pressure after standing was at least 240 kPa and 250 kPa or less. 4: The air pressure after standing was at least 230 kPa and less than 240 kPa. 3: The air pressure after standing was at least 220 kPa and less than 230 kPa 2: The air pressure after standing was at least 200 kPa and less than 220 kPa 1: The air pressure after standing was less than 200 kPa Flowability of the sealant

[0042] The test tire was mounted on a wheel with a rim size of 20×9J and mounted on a drum testing machine, and was run at an air pressure of 220 kPa, a load of 8.5 kN and three levels of running speeds of 100 km / h, 150 km / h and 200 km / h for one hour at each speed, and after running at each speed, the flow state of the sealant was examined.For the evaluation results, lines of 20×40 squares with a grid pitch of 5 mm each were drawn in a surface of the sealant layer before the run, and the number of squares with distorted shape was counted after the run, wherein the case where no flow of the sealant was observed (the number of distorted squares is 0) was recorded as “Good”, the case where the number of distorted squares was less than 1 / 4 of the total number of squares was recorded as “Pass”, and the case where the number of distorted squares was 1 / 4 or greater than the total number of squares was recorded as “Fail”. [Table 1-I] Table 1-I Comparison example 1 Comparison example 2 Comparison example 3 Example 1 Example 2 Reference example 3 Halogenated IIR 1 Mass-produced parts 10 10 1 10 10 Halogenated IIR 2 Mass-produced parts 100 90 90 99 90 Non-halogenated IIR Mass-produced parts 90 Natural rubber Mass-produced parts Organic peroxide Mass-produced parts 10 0,1 10 10 10 10 Crosslinking agent 1 Mass-produced parts 1 1 1 1 Crosslinking agent 2 Mass-produced parts Crosslinking agent 3 Mass-produced parts Crosslinking agent 4 Mass-produced parts Networking Aid 1 Mass-produced parts Networking Aid 2 Mass-produced parts 5 5 5 5 5 5 Networking Aid 3 Mass-produced parts Liquid Polymer 1 Mass-produced parts 200 200 200 200 200 200 Liquid Polymer 2 Mass-produced parts Liquid Polymer 3 Mass-produced parts Sealing properties Initial performance 5 1 5 5 5 5 After heat decomposition acceleration treatment 5 1 5 4 4 5 Flowability 100 km / h Good Good Failed Good Good Good 150 km / h Failed Good Failed Good Good Good 200 km / h Failed Passed Failed Good Good Good [Table 1-II] Table 1-II Example 4 REFERENCE ENZBE I-GAME 5 REFERENCE ENZBE I-GAME 6 REFERENCE ENZBE I-GAME 7 EXAMPLE 8 EXAMPLE 9 Halogenated IIR 1 Mass-produced parts 50 50 100 100 10 10 Halogenated IIR Mass-produced parts 50 90 90 Non-halogenated Mass-produced parts 50 Natural rubber Mass-produced parts Organic peroxide Mass-produced parts 10 10 10 10 10 10 Crosslinking agent 1 Mass-produced parts 1 1 1 1 Crosslinking agent 2 Mass-produced parts 1 Crosslinking agent 3 Mass-produced parts 1 Crosslinking agent 4 Mass-produced parts Networking Aid 1 Mass-produced parts 5 5 Networking Aid 2 Mass-produced parts 5 5 5 Networking Help 3 Mass-produced parts 5 Liquid Polymer 1 Mass-produced parts 200 200 200 200 200 200 Liquid Polymer 2 Mass-produced parts Liquid Polymer 3 Mass-produced parts Sealing properties Initial performance 4 4 5 5 5 5 After heat decomposition acceleration treatment 3 4 3 3 3 3 Flowability 100 km / h Good Good Good Good Good Good 150 km / h Good Good Good Good Good Good 200 km / h Good Good Good Good Passed Passed [Table 2-I] Table 2-I EXAMPLE 10 EXAMPLE 11 EXAMPLE 12 EXAMPLE 13 EXAMPLE 14 Halogenated IIR 1 Mass-produced parts 10 10 10 10 10 Halogenated IIR 2 Mass-produced parts 90 90 90 90 90 Non-halogenated IIR Mass-produced parts Natural rubber Mass-produced parts Organic peroxide Mass-produced parts 1 40 10 10 10 Crosslinking agent 1 Mass-produced parts 1 1 0,1 40 1 Crosslinking agent 2 Mass-produced parts Crosslinking agent 3 Mass-produced parts Crosslinking agent 4 Mass-produced parts Networking Help 1 Mass-produced parts Networking Aid 2 Mass-produced parts 5 5 5 5 5 Networking Help 3 Mass-produced parts Liquid Polymer 1 Mass-produced parts 200 200 200 200 50 Liquid Polymer 2 Mass-produced parts Liquid Polymer 3 Mass-produced parts Sealing properties Initial performance 4 5 5 3 3 After heat decomposition acceleration treatment 3 4 4 3 3 Flowability 100 km / h Good Good Good Good Good 150 km / h Good Good Good Good Good 200 km / h Good Passed Passed Good Good [Table 2-II] Table 2-II EXAMPLE 15 EXAMPLE 16 EXAMPLE 17 EXAMPLE 18 EXAMPLE 19 Halogenated IIR 1 Mass-produced parts 10 10 10 10 10 Halogenated IIR 2 Mass-produced parts 90 90 90 90 90 Non-halogenated IIR Mass-produced parts Natural rubber Organic peroxide Mass-produced parts 10 10 10 10 10 Crosslinking agent 1 Mass-produced parts 1 1 1 1 1 Crosslinking agent 2 Mass-produced parts Crosslinking agent 3 Mass-produced parts Crosslinking agent 4 Mass-produced parts Networking Aid 1 Mass-produced parts Networking Aid 2 Mass-produced parts 5 5 5 5 5 Networking Aid 3 Mass-produced parts Liquid Polymer 1 Mass-produced parts 400 Liquid Polymer 2 Mass-produced parts 200 50 400 Liquid Polymer 3 Mass-produced parts 200 Sealing properties Initial performance 5 5 3 5 5 After heat decomposition acceleration treatment 4 5 2 4 4 Flowability 100 km / h Good Good Good Good Good 150 km / h Good Good Good Good Good 200 km / h Passed Passed Good Passed Passed [Table 3-I] Table 3-I EXAMPLE 20 EXAMPLE 21 REFERENCE ENZBE I-GAME 22 REFERENCE ENZBE I-GAME 23 EXAMPLE 24 EXAMPLE 25 Halogenated IIR 1 Mass-produced parts 80 40 10 80 80 Halogenated IIR 2 Mass-produced parts 10 40 10 10 10 Non-halogenated IIR Mass-produced parts Natural rubber Mass-produced parts 10 10 90 10 10 10 Organic peroxide Mass-produced parts 10 10 10 10 10 10 Networking Center 1 Mass-produced parts 1 1 1 1 1 1 Crosslinking agent 2 Mass-produced parts Crosslinking agent 3 Mass-produced parts Crosslinking agent 4 Mass-produced parts Networking Aid 1 Mass-produced parts 0,5 0,5 0,5 0,5 0,9 0,1 Networking Aid 2 Mass-produced parts Networking Aid 3 Mass-produced parts Liquid Polymer 1 Mass-produced parts Liquid Polymer 2 Mass-produced parts 200 200 200 200 200 200 Liquid Polymer 3 Mass-produced parts Sealing properties Initial performance 5 5 3 3 4 4 After heat decomposition acceleration treatment 4 4 3 3 3 4 Flowability 100 km / h Good Good Good Good Good Good 150 km / h Good Good Good Good Good Good 200 km / h Good Good Good Passed Good Good [Table 3-II] Table 3-II Example 26 Comparison example 4 Example 27 Example 28 Example 29 Halogenated IIR 1 Mass-produced parts 80 80 80 80 80 Halogenated IIR 2 Mass-produced parts 10 10 10 10 10 Non-halogenated IIR Mass-produced parts Natural rubber Mass-produced parts 10 10 10 10 10 Organic peroxide Mass-produced parts 1 0 0,5 10 10 10 Crosslinking agent 1 Mass-produced parts 1 1 1 Crosslinking agent 2 Mass-produced parts 1 1 Crosslinking agent 3 Mass-produced parts Crosslinking agent 4 Mass-produced parts 0,5 Networking Aid 1 Mass-produced parts 0,5 Networking Aid 2 0,5 0,5 Networking Aid 3 Mass-produced parts 0,5 Liquid Polymer 1 Mass-produced parts Liquid Polymer 2 Mass-produced parts 200 200 200 200 200 Liquid Polymer 3 Mass-produced parts Sealing properties Initial performance 4 3 4 4 4 After heat decomposition acceleration treatment 4 2 3 4 4 Flowability 100 km / h Good Failed Good Good Good 150 km / h Good Failed Good Good Good 200 km / h Good Failed Good Good Good [Table 4-I] Table 4-I Example 30 Comparison example 5 Comparison example 6 Example 31 Example 32 Halogenated IIR 1 Mass-produced parts 10 80 80 80 Halogenated IIR 2 Mass-produced parts 80 10 10 10 Non-halogenated IIR Mass-produced parts Natural rubber Mass-produced parts 10 100 10 10 10 Organic peroxide Mass-produced parts 10 10 0,5 1 40 Crosslinking agent 1 Mass-produced parts 1 1 1 1 1 Crosslinking agent 2 Mass-produced parts Crosslinking agent 3 Mass-produced parts Crosslinking agent 4 Mass-produced parts Networking Aid 1 Mass-produced parts 0,9 0,5 0,5 0,5 0,5 Networking Aid 2 Mass-produced parts Networking Aid 3 Mass-produced parts Liquid Polymer 1 Mass-produced parts Liquid Polymer 2 Mass-produced parts 200 200 200 200 200 Liquid Polymer 3 Mass-produced parts Sealing properties Initial performance 4 1 4 4 5 After heat decomposition acceleration treatment, 4 1 4 4 5 Flowability 100 km / h Good Good Good Good Good 150 km / h Good Good Good Good Good 200 km / h Good Good Good Good Passed [Table 4-II] Table 4-II Comparison example 7 Example 33 Example 34 Example 35 Example 36 Halogenated IIR 1 Mass-produced parts 10 10 10 80 80 Halogenated IIR 2 Mass-produced parts 80 80 80 10 10 Non-halogenated IIR Mass-produced parts Natural rubber Mass-produced parts 10 10 10 10 10 Organic peroxide Mass-produced parts 10 10 10 0,5 0,5 Crosslinking agent 1 Mass-produced parts 0,05 0,1 40 1 1 Crosslinking agent 2 Mass-produced parts Crosslinking agent 3 Mass-produced parts Crosslinking agent 4 Mass-produced parts Networking Aid 1 Mass-produced parts 0,5 0,5 0,5 0,5 0,5 Networking Aid 2 Mass-produced parts Networking Aid 3 Mass-produced parts Liquid Polymer 1 Mass-produced parts Liquid Polymer 2 Mass-produced parts 200 200 200 50 400 Liquid Polymer 3 Mass-produced parts Sealing properties Initial performance 4 4 4 3 3 After heat decomposition acceleration treatment 4 4 4 3 3 Flowability 100 km / h Failed Good Good Good Good 150 km / h Failed Good Good Good Passed 200 km / h Failed Passed Good Good Passed

[0043] The starting material types used in Tables 1 and 2 are described below. • Halogenated IIR 1: Chlorinated butyl rubber, CHLORBUTYL 1066, available from JSR Corporation • Halogenated IIR 2: Brominated butyl rubber, BROMBUTYL 2222, available from JSR Corporation • Non-halogenated IIR: BUTYL 065, available from JSR Corporation • Natural rubber: Natural rubber, available from SRI TRANG • Organic peroxide: Dibenzoyl peroxide, NYPER NS, available from NOF Corp. (1-minute half-life temperature: 133 °C) • Crosslinking agent 1: Sulfur, small pieces of sulfur, available from Hosoi Chemical Industry Co., Ltd. • Crosslinking agent 2: Cyclic sulfide, VALNOC R, available from Ouchi Shinko Chemical Industrial Co., Ltd. • Crosslinking agent 3: Phenolic resin, TD-2620, available from DIC Corporation • Crosslinking agent 4: Quinone dioxime, VALNOC GM, available from Ouchi Shinko Chemical Industrial Co., Ltd. • Crosslinking aid 1: Thiazole-based vulcanization accelerator, NOCCELER MZ, available from Ouchi Shinko Chemical Industrial Co. Ltd. • Crosslinking aid 2: Thiuram-based vulcanization accelerator, NOCCELER DM-PO, available from Ouchi Shinko Chemical Industrial Co., Ltd. • Crosslinking aid 3: Guanidine-based vulcanization accelerator, NOCCELER D, available from Ouchi Shinko Chemical Industrial Co. Ltd. • Liquid Polymer 1: Liquid butyl rubber, Kalene 800, available from Royal Elastomers (molecular weight: 36000) • Liquid Polymer 2: Paraffin oil, Diana Process PW-380, available from Idemitsu Kosan Co., Ltd. (molecular weight: 1500) • Liquid Polymer 3: Paraffin oil, Diana Process K-350, available from Idemitsu Kosan Co., Ltd. (molecular weight: 800)

[0044] As shown in Tables 1 and 2, the pneumatic tires of Examples 1 to 19 each suppressed sealant flow while exhibiting good sealing properties. In particular, sealant flow was effectively suppressed even during high-speed driving. Furthermore, as shown in Tables 3 and 4, the pneumatic tires of Examples 20 to 36 each suppressed sealant flow regardless of the driving speed while exhibiting good sealing properties both for the initial performance and after the heat decomposition acceleration treatment, providing these performances in a well-balanced, compatible manner.

[0045] On the other hand, in Comparative Example 1, since the sealant material composition did not contain chlorinated butyl rubber, the flowability of the sealant deteriorated during high-speed driving. In Comparative Example 2, since the blended amount of the organic peroxide was small, the sealing properties deteriorated. In Comparative Example 3, since no crosslinking agent was included, the flowability deteriorated under all speed conditions. In Comparative Example 4, since less than 1 part by mass of the organic peroxide was included, the sealing properties deteriorated (note that for Comparative Example 4, it is assumed that blending quinone dioxime instead of the crosslinking aid also contributed to the reduction in the sealing properties).In Comparative Example 5, since no butyl rubber was blended, the sealing properties (initial performance and after heat decomposition acceleration treatment) were deteriorated. In Comparative Example 6, since the blended amount of organic peroxide was small, the sealing properties (initial performance and after heat decomposition acceleration treatment) were deteriorated. In Comparative Example 7, since the blended amount of the crosslinking agent was small, the flowability was deteriorated under all driving speed conditions. List of reference symbols 1 tread section 2 side wall section 3 bead section 4 carcass layers 5 Bead core 6 bead fillers 7th belt layer 8 Belt reinforcement layer 9 inner soul layer 10 Sealant layer CL Tire Equator

Claims

[1] A sealing material composition forming a sealant layer disposed on an inner surface of a pneumatic tire, the sealing material composition comprising: 1 part to 40 parts by mass of an organic peroxide; 0.1 parts by mass to 40 parts by mass of a crosslinking agent blended per 100 parts by mass of a rubber component comprising a chlorinated butyl rubber; and another halogenated butyl rubber besides the chlorinated butyl rubber. [2] The sealant material composition according to claim 1, wherein the crosslinking agent comprises a sulfur component. [3] The sealing material composition according to claim 1 or 2, wherein 50 parts by mass to 400 parts by mass of a liquid polymer are blended for 100 parts by mass of the rubber component. [4] The sealing material composition according to claim 3, wherein the liquid polymer is paraffin oil. [5] The sealing material composition according to claim 4, wherein a molecular weight of the paraffin oil is 800 or more. [6] Sealant material composition according to any one of claims 1 to 5, which comprises a crosslinking aid. [7] The sealing material composition according to claim 6, wherein the crosslinking aid is a thiazole-based compound or a thiuram-based compound. [8] The sealing material composition according to claim 6 or 7, wherein a blended amount of the crosslinking aid is 50 mass% to 400 mass% of a blended amount of the crosslinking agent. [9] A pneumatic tire comprising a sealant layer formed from the sealant material composition according to any one of claims 1 to 8.

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