Adhesive sealant

Abstract

To provide an adhesive sealant material capable of exhibiting good sealability even under a low-temperature environment, suppressing flow during travel, securing sufficient adhesiveness to a tire, and satisfactorily maintaining these performances over a long period of time.SOLUTION: An adhesive sealant material constituting a sealant layer 10 arranged on an inner surface of a pneumatic tire is composed of a sealant material composition which contains 0.1-40 pts.mass of sulfur, more than 0 pt.mass and less than 1 pt.mass of a crosslinking aid, and 50 pts.mass or more of a plasticizer component based on 100 pts.mass of a rubber component. Viscosity V1 measured under a condition of -20°C immediately after vulcanization is set to 20 kPa s or less, and a viscosity difference ΔV between the viscosity V1 and viscosity V2 measured under a condition of -20°C after storage for two weeks in a 30°C environment from immediately after vulcanization is set to 5 kPa s or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an adhesive sealant material that constitutes a sealant layer of 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 (a so-called self-sealing type 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 traveling.

[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 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, it is required for the sealant composition constituting the sealant to have a good balance between suppressing the flow of the sealant during driving and ensuring good sealing performance.

[0004] In addition, the viscosity of a sealant generally depends on temperature, and the lower the temperature, the higher the viscosity. Therefore, in a low-temperature environment such as when used in winter or in a cold region, the viscosity of the sealant increases, and there is a risk of the sealability being impaired. Furthermore, depending on the temperature conditions, the sealant may solidify, and when a foreign object such as a nail penetrates the tread portion, the impact may cause a part of the sealant around the through hole to be chipped, and the through hole may not be properly sealed. Therefore, the sealant composition constituting the sealant is required to exhibit good sealability even in a low-temperature environment.

[0005] Furthermore, since the sealant only functions when a puncture occurs, it remains in the tire until a puncture occurs. Therefore, there is a risk that the components contained in the sealant will migrate to the rubber that constitutes the tire, impairing the adhesiveness of the sealant to the tire and causing the sealant to peel off during driving. Therefore, the sealant is required to maintain its performance as a sealant over a long period of time, specifically, its adhesiveness to the tire in addition to the above-mentioned sealing property and fluidity. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2006-152110 A Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide an adhesive sealant material that exhibits good sealing properties even in low-temperature environments, suppresses flow during driving, ensures sufficient adhesion to tires, and further enables these performance properties to be maintained well over a long period of time. [Means for solving the problem]

[0008] The adhesive sealant of the present invention for achieving the above object is an adhesive sealant constituting a sealant layer disposed on the inner surface of a pneumatic tire, and is composed of a sealant composition containing 0.1 to 40 parts by mass of sulfur, more than 0 part by mass and less than 1 part by mass of a cross-linking aid, and 50 parts by mass or more of a plasticizer component, relative to 100 parts by mass of a rubber component; the plasticizer component is selected from paraffin oil, polybutene oil, polyisobutene oil, and aromatic oil; The composition is characterized in that the viscosity V1 measured at -20°C immediately after vulcanization is 20 kPa s or less, and the viscosity difference ΔV between the viscosity V1 and the viscosity V2 measured at -20°C after storage in a 30°C environment for two weeks immediately after vulcanization is 5 kPa s or less. Effect of the Invention

[0009] The adhesive sealant of the present invention is composed of the sealant composition of the above-mentioned formulation and has the above-mentioned characteristics, so that it exhibits good sealing properties even in low-temperature environments, suppresses the flow of the sealant during driving, and ensures sufficient adhesion to tires, and furthermore, can maintain these performances well for a long period of time. In particular, since it contains sulfur (crosslinked by sulfur), it can increase adhesion to the inner surface of the tire, and the above-mentioned formulation is advantageous in achieving a good balance between these performances by obtaining a suitable elasticity that does not flow during driving or storage while ensuring sufficient viscosity to obtain good sealing properties. In addition, the above-mentioned formulation can reduce the temperature dependency of the physical properties of the adhesive sealant, which is advantageous in achieving a good balance between sealing properties and flow properties in low-temperature environments. In addition, the viscosity V1 can be set within the above-mentioned range to ensure sealing properties in low-temperature environments, and furthermore, by setting the viscosity difference ΔV as described above, the plasticizer component contained in the adhesive sealant can be prevented from migrating over time to the rubber constituting the tire, and the performance of the adhesive sealant can be maintained well for a long period of time. In the present invention, the "viscosity" is a value measured using a rotational viscometer under specified temperature conditions in accordance with JIS K6833-1: 2008. In particular, the viscosity V1 is a value measured by cooling the adhesive sealant immediately after vulcanization at -20°C for 24 hours, and the viscosity V2 is a value measured by cooling the adhesive sealant immediately after vulcanization at -20°C for 24 hours after storing it in a 30°C environment for 2 weeks.

[0010] In the adhesive sealant of the present invention, the viscosity difference ΔV between the viscosity V1 and the viscosity V2 is preferably 3 kPa s or less, which is advantageous for ensuring sufficient sealing properties in low-temperature environments and for maintaining good performance of the adhesive sealant over a long period of time.

[0011] The adhesive sealant of the present invention is preferably blended with 1 to 40 parts by mass of an organic peroxide per 100 parts by mass of the rubber component. By containing an organic peroxide in this way and crosslinking by the combined use of sulfur and organic peroxide, it is advantageous to obtain a suitable elasticity that does not flow during driving or storage while securing sufficient viscosity to obtain good sealing properties, and to achieve a good balance between these performances. In addition, by using such a blend, it is possible to reduce the temperature dependency of the physical properties of the adhesive sealant, which is advantageous to achieve a good balance between sealing properties, storage properties, and flow properties in a low-temperature environment.

[0012] The adhesive sealant of the present invention preferably contains 10% by mass or more of butyl rubber relative to 100% by mass of the rubber component. Furthermore, it is preferable that the butyl rubber contains chlorinated butyl rubber, and the content of the chlorinated butyl rubber relative to 100% by mass of the rubber component is 5% by mass or more. By using such a blending method, the adhesion to the inner surface of a tire can be improved.

[0013] In the adhesive sealant of the present invention, the plasticizer component is preferably a liquid polymer. In particular, the liquid polymer is preferably paraffin oil. Furthermore, the molecular weight of the paraffin oil is preferably 800 or more. This makes it possible to reduce the temperature dependency of the physical properties of the adhesive sealant, which is advantageous in ensuring good sealing properties in low-temperature environments.

[0014] The adhesive sealant of the present invention is preferably vulcanized under conditions of a vulcanization temperature of 150° C. or higher and a vulcanization time of 5 to 60 minutes. By carrying out vulcanization under these conditions, it is possible to suppress the remaining unreacted sulfur in the adhesive sealant, which is advantageous for maintaining the performance of the adhesive sealant at a good level for a long period of time.

[0015] In a pneumatic tire provided with a sealant layer made of the adhesive sealant of the present invention described above, the excellent physical properties of the adhesive sealant described above allow the adhesive sealant to exhibit good sealing properties while suppressing the flow of the adhesive sealant during driving, and in particular, good sealing properties can be ensured even in low temperature environments. Furthermore, the above-mentioned blending and physical properties prevent the plasticizer component contained in the adhesive sealant from migrating over time to the rubber constituting the tire, so that the performance of the adhesive sealant can be maintained at a good level over a long period of time. [Brief description of the drawings]

[0016] [Figure 1] 1 is a meridian cross-sectional view showing an example of a pneumatic tire of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The configuration of the present invention will be described in detail below with reference to the accompanying drawings.

[0018] 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.

[0019] 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.

[0020] 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°.

[0021] 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.

[0022] As shown in FIG. 1, a sealant layer 10 is provided on the inner side of the inner liner layer 9 in the tread portion 1 in the tire radial direction. In particular, the sealant layer 10 is provided on the inner surface of the tire corresponding to the ground contact area of ​​the tread portion 1, that is, an area where a foreign object such as a nail may be stuck during running. In particular, it is preferable to provide the sealant layer 10 in an area wider than the width of the minimum belt layer 7a. The sealant material composition of the present invention is used for this sealant layer 10. The sealant layer 10 is attached to the inner surface of a pneumatic tire having the above-mentioned basic structure. For example, when a foreign object such as a nail is stuck in the tread portion 1, the adhesive 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 the tire to continue running.

[0023] The sealant layer 10 has a thickness of, for example, 0.5 mm to 5.0 mm. With a thickness of this order, 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. The thickness of the sealant layer 10 is an average thickness.

[0024] The sealant layer 10 can be formed by subsequently attaching it to the inner surface of a vulcanized pneumatic tire. For example, an adhesive sealant obtained by vulcanizing a sealant composition described below may be attached to the inner surface of the tire to form the sealant layer 10. When attaching the adhesive sealant, an adhesive sealant molded in a sheet shape may be attached over the entire circumference of the inner surface of the tire, or an adhesive sealant molded in a string or band shape may be attached in a spiral shape to the inner surface of the tire.

[0025] The vulcanization conditions for vulcanizing the sealant composition described below to obtain the above-mentioned adhesive sealant are not particularly limited, but considering the composition of the sealant composition described below and the physical properties required for the adhesive sealant, the vulcanization temperature is preferably 150° C. or higher, more preferably 160° C. to 200° C., and the vulcanization time is preferably 5 minutes to 60 minutes, more preferably 10 minutes to 30 minutes. By performing vulcanization under these conditions, it is possible to suppress the remaining unreacted sulfur in the adhesive sealant, which is advantageous for maintaining the performance of the adhesive sealant well over a long period of time.

[0026] Since the present invention mainly relates to an adhesive sealant material (sealant material composition) used in the sealant layer 10 of the above-mentioned self-sealing type pneumatic tire, the basic structure of the pneumatic tire and the structure of the sealant layer 10 are not limited to the above-mentioned examples.

[0027] Regarding the adhesive sealant of the present invention, the viscosity measured at −20° C. immediately after vulcanization is V1, and the viscosity measured at −20° C. after storing in a 30° C. environment for 2 weeks immediately after vulcanization is V2. The viscosity V1 is 20 kPa·s or less, preferably 5 kPa·s to 15 kPa·s, and the viscosity difference ΔV between the viscosity V1 and the viscosity V2 is 5 kPa·s or less, preferably 3 kPa·s or less. When the adhesive sealant having such characteristics is used in the sealant layer 10 of a pneumatic tire, the viscosity V1 is sufficiently low to exhibit good sealing properties even in a low-temperature environment, and the viscosity difference ΔV is small to maintain the performance of the adhesive sealant for a long period of time. At this time, if the viscosity V1 exceeds 20 kPa·s, the sealing properties in a low-temperature environment are deteriorated. If the viscosity difference ΔV exceeds 5 kPa·s, it becomes difficult to maintain the performance of the adhesive sealant for a long period of time.

[0028] The viscosity V2 is not particularly limited as long as it is within the range calculated from the range of the viscosity V1 and the range of the viscosity difference ΔV described above, but is preferably 5 kPa·s to 20 kPa·s, and more preferably 7 kPa·s to 15 kPa·s.

[0029] The adhesive sealant of the present invention has the above-mentioned physical properties and is composed of a sealant composition having the following composition (hereinafter referred to as the sealant composition of the present invention).

[0030] In the 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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 any blend.

[0035] In the sealant composition of the present invention, sulfur is always blended as a crosslinking agent. The blending amount of sulfur is 0.1 to 40 parts by mass, preferably 0.5 to 20 parts by mass, based on 100 parts by mass of the rubber component. This allows the adhesive sealant to be crosslinked by sulfur, improving its adhesion to tires. If the blending amount of sulfur is less than 0.1 parts by mass, it is essentially the same as not containing a crosslinking agent, and appropriate crosslinking cannot be performed. If the blending amount of sulfur exceeds 40 parts by mass, crosslinking of the sealant composition proceeds too much, resulting in a decrease in sealing properties. Note that even if a crosslinking agent other than sulfur (e.g., quinone dioxime, zinc oxide, etc.) is used, it is not possible to ensure sufficient adhesion to tires.

[0036] In the sealant composition of the present invention, it is preferable to compound an organic peroxide together with the above-mentioned crosslinking agent (sulfur). By compounding sulfur and an organic peroxide in combination in this way, suitable crosslinking can be realized to ensure both sealing properties and prevention of flow of the sealant. The compounded 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 compounded 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 compounded amount of the organic peroxide exceeds 40 parts by mass, crosslinking of the sealant composition proceeds too much, resulting in a decrease in sealing properties.

[0037] In using sulfur and an organic peroxide in combination in this way, the mass ratio A / B of the amount of sulfur blended A to the amount of organic peroxide blended B is preferably 5 / 1 to 1 / 200, more preferably 1 / 10 to 1 / 20. By using such a blending ratio, it is possible to achieve a better balance between ensuring sealing properties and preventing the flow of the sealant.

[0038] 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.

[0039] The sealant composition of the present invention is necessarily blended with a crosslinking aid together with the crosslinking agent (sulfur). The crosslinking aid is a compound that acts as a crosslinking reaction catalyst when blended with a crosslinking agent containing a sulfur component. By blending the crosslinking agent (sulfur) and the crosslinking aid, the vulcanization speed can be increased, and the productivity of the sealant composition can be improved. The blending 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 blending 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 blending 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 blended 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.

[0040] When the crosslinking agent (sulfur) and the crosslinking assistant are used in combination, the amount of the crosslinking agent (sulfur) is preferably 50% by mass to 400% by mass, more preferably 100% by mass to 200% by mass of the amount of the crosslinking assistant. By blending the crosslinking agent (sulfur) and the crosslinking assistant in a well-balanced manner, the function of the crosslinking assistant as a catalyst can be well exhibited, which is advantageous for ensuring both sealing properties and preventing the sealant from flowing. If the amount of the crosslinking agent (sulfur) is less than 50% by mass of the amount of the crosslinking assistant, the flowability decreases. If the amount of the crosslinking agent (sulfur) is more than 400% by mass of the amount of the crosslinking assistant, the deterioration resistance decreases.

[0041] 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.

[0042] 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 (sulfur) as described above, quinone dioxime does not correspond to the crosslinking auxiliary in the present invention.

[0043] A plasticizer component (e.g., liquid polymer) is always blended into the sealant composition of the present invention. By blending the plasticizer component in this manner, the viscosity of the adhesive sealant can be increased to improve the sealing property. The blending amount of the plasticizer component is 50 parts by mass or more, preferably 50 to 400 parts by mass, and more preferably 70 to 200 parts by mass, relative to 100 parts by mass of the rubber component. If the blending amount of the plasticizer component is less than 50 parts by mass, the effect of increasing the viscosity of the adhesive sealant may not be sufficiently obtained. If the blending amount of the plasticizer component exceeds 400 parts by mass, the flow of the sealant cannot be sufficiently prevented.

[0044] As the plasticizer component, liquid polymers can be exemplified as described above, and liquid polymers that can be co-crosslinked with the rubber component (butyl rubber) in the sealant material composition are particularly preferred. Examples of such liquid polymers include paraffin oil, polybutene oil, polyisoprene oil, polybutadiene oil, polyisobutene oil, aromatic oil, and polypropylene glycol. From the viewpoint of keeping the temperature dependency of the physical properties of the sealant material composition low 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 in a low-temperature environment to an appropriate range. 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 plasticizer component (oil content) from migrating from the sealant layer provided on the inner surface of the tire to the tire body and affecting the tire.

[0045] The adhesive sealant of the present invention exhibits good sealing properties even in low-temperature environments by combining the above-mentioned physical properties (viscosity) and formulation, and suppresses the flow of the sealant during driving, and furthermore, can maintain these properties well over a long period of time. In particular, by including sulfur (crosslinking with sulfur), the adhesive sealant can enhance adhesion to the inner surface of the tire, and by using the above-mentioned formulation, it is possible to obtain a suitable elasticity that does not flow during driving or storage while securing sufficient viscosity to obtain good sealing properties, and thus achieve both of these properties in a well-balanced manner. Furthermore, by using the above-mentioned formulation, it is possible to reduce the temperature dependency of the physical properties of the sealant composition, and it is possible to achieve a good balance between sealing properties and flow properties in a low-temperature environment. In addition, by setting the viscosity V1 within the above-mentioned range, it is possible to ensure sealing properties in a low-temperature environment, and furthermore, by setting the viscosity difference ΔV as described above, it is possible to prevent the plasticizer component contained in the adhesive sealant from migrating over time to the rubber constituting the tire, and it is possible to maintain the performance of the adhesive sealant well over a long period of time. Therefore, the adhesive sealant of the present invention can be suitably used for the sealant layer 10 of a self-sealing type pneumatic tire. A tire provided with a sealant layer 10 made of the adhesive sealant of the present invention can reliably seal through holes caused by punctures even in low temperature environments due to the excellent performance of the adhesive sealant based on the cooperation of the above-mentioned physical properties and compounding, and can maintain this performance for a long period of time.

[0046] 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

[0047] The sealant compositions were prepared according to the compositions shown in Tables 1 and 2. Specifically, the rubber component and carbon black were mixed in a 1.7 L Banbury mixer for 10 minutes, then the plasticizer component (liquid polymer) was added, and finally the crosslinker (sulfur) and organic peroxide were added and mixed for another 10 minutes to prepare each sealant composition. The sealant compositions were vulcanized under the conditions shown in Tables 1 and 2 to obtain adhesive sealants (Comparative Examples 1 to 10, Examples 1 to 5).

[0048] Tables 1-2 also show the viscosities of the adhesive sealant. Viscosity V1 is the viscosity of the adhesive sealant immediately after vulcanization, and is a value measured by cooling the adhesive sealant of each example at -20°C for 24 hours immediately after vulcanization under the conditions of each example shown in Tables 1-2. Viscosity V2 is the viscosity of the adhesive sealant immediately after vulcanization and after storage for 2 weeks in a 30°C environment, and is a value measured by cooling the adhesive sealant after storage at -20°C for 24 hours. Viscosity V3 is the viscosity of the adhesive sealant immediately after storage for 10 days in a 25°C environment immediately after vulcanization, and is a value measured by cooling the adhesive sealant after storage at -20°C for 24 hours. Each viscosity was measured using a rotational viscometer in accordance with JIS K6833-1:2008.

[0049] These adhesive sealants were evaluated for sealing ability, adhesion, and fluidity during driving by the following test methods, and the results are shown in Tables 1 and 2.

[0050] Sealing ability (condition 1) Each adhesive sealant immediately after vulcanization was attached to the inner side of the inner liner layer in the tread of a pneumatic tire (tire size: 255 / 40R20) having the basic structure shown in Figure 1 to produce a test tire. Then, each test tire was cooled at a temperature of -20°C for 24 hours, and then mounted on a wheel with a rim size of 20 x 9J and mounted on a test vehicle. A nail with a diameter of 4.0 mm was driven into the tread under conditions of an initial air pressure of 250 kPa, a load of 8.5 kN, and a temperature of -20°C. Furthermore, the air pressure was measured after the tire was left for 1 hour in an environment at -20°C with the nail removed. The evaluation results were shown on a 5-point scale as follows. Note that if the evaluation result score is "3" or higher, sufficient sealing ability was exhibited, and the higher the score, the better the sealing ability was exhibited. 5: Air pressure after standing is 240kPa or more and 250kPa or less 4: Air pressure after standing is 230kPa or more and less than 240kPa 3: Air pressure after standing is 215kPa or more and less than 230kPa 2: Air pressure after standing is 200kPa or more and less than 215kPa 1: Air pressure after standing is less than 200kPa

[0051] Sealing ability (condition 2) Each adhesive sealant material was attached to the inner liner layer in the tread portion of a pneumatic tire (tire size: 255 / 40R20) having the basic structure shown in FIG. 1 on the radially inner side of the tread portion to produce a test tire, which was then stored in a 30°C environment for two weeks. Each test tire was then cooled for 24 hours at a temperature of -20°C, after which it was mounted on a wheel with a rim size of 20×9J and mounted on a test vehicle. A nail with a diameter of 4.0 mm was driven into the tread portion under conditions of an initial air pressure of 250 kPa, a load of 8.5 kN, and a temperature of -20°C, and the air pressure was measured after the tire was left standing in a -20°C environment for one hour with the nail removed. The evaluation results were shown on a five-point scale. If the evaluation result score was "3" or higher, sufficient sealing performance was exhibited, and the higher the score, the better the sealing performance was exhibited. 5: Air pressure after standing is 240kPa or more and 250kPa or less 4: Air pressure after standing is 230kPa or more and less than 240kPa 3: Air pressure after standing is 215kPa or more and less than 230kPa 2: Air pressure after standing is 200kPa or more and less than 215kPa 1: Air pressure after standing is less than 200kPa

[0052] Adhesion (condition 1) Each adhesive sealant immediately after vulcanization was attached to the inner side of the inner liner layer in the tread of a pneumatic tire (tire size: 255 / 40R20) having the basic structure shown in Figure 1 to produce a test tire. Each test tire was then mounted on a wheel with a rim size of 20 x 9J and mounted on a test vehicle. After running 100,000 km under the conditions of an air pressure of 250 kPa, a load of 5.0 kN, and a speed of 80 km / h, the peeling state of the adhesive sealant at the splice of the adhesive sealant was visually confirmed. The evaluation results were as follows: "Good" if no peeling occurred, "Fair" if the area where peeling occurred was less than 1 / 3 of the width of the sealant layer from the end of the splice in the tire width direction, and "Not Good" if the area where peeling occurred was 1 / 3 or more of the width of the sealant layer from the end of the splice in the tire width direction.

[0053] Adhesion (condition 2) Each adhesive sealant was attached to the inner radial side of the inner liner layer in the tread of a pneumatic tire (tire size: 255 / 40R20) having the basic structure shown in FIG. 1 to produce a test tire, which was then stored in an environment at 30°C for two weeks. Each test tire was then mounted on a wheel with a rim size of 20×9J and mounted on a test vehicle, and the tire was driven for 100,000 km under the conditions of an air pressure of 250 kPa, a load of 5.0 kN, and a speed of 80 km / h. After that, the peeling state of the adhesive sealant at the splice of the adhesive sealant was visually confirmed. The evaluation results were as follows: "Good" if no peeling occurred, "Fair" if the area where peeling occurred was less than 1 / 3 of the width of the sealant layer from the end of the splice in the tire width direction, and "Not Good" if the area where peeling occurred was 1 / 3 or more of the width of the sealant layer from the end of the splice in the tire width direction.

[0054] Fluidity during driving Each adhesive sealant immediately after vulcanization was attached to the inner radial side of the inner liner layer in the tread of a pneumatic tire (tire size: 255 / 40R20) having the basic structure shown in Figure 1 to produce a test tire. The test tire was then mounted on a wheel with a rim size of 20 x 9J and mounted on a drum testing machine, and the tire was driven for 1 hour under the conditions of an air pressure of 220 kPa, a load of 8.5 kN, and a running speed of 100 km / h, and the flow state of the adhesive sealant after the run was examined. The evaluation results were obtained by drawing 20 x 40 squares of 5 mm grid lines 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 flow of the adhesive sealant was observed at all (the number of distorted squares was 0), it was indicated as "good", if the number of distorted squares was less than 1 / 4 of the total, it was indicated as "passable", and if the number of distorted squares was 1 / 4 or more of the total, it was indicated as "not good".

[0055] [Table 1]

[0056] [Table 2]

[0057] The types of raw materials used in Tables 1 and 2 are shown below. Chlorinated butyl rubber: JSR CHLOROBUTYL1066 Natural rubber: SRI TRANG natural rubber Carbon black: Seast KH manufactured by Tokai Carbon Co., Ltd. Sulfur: small lump sulfur manufactured by Hosoi Chemical Industries Quinone dioxime: Valnoc GM manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Crosslinking aid: Thiuram-based vulcanization accelerator, Noccela TT-P manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Organic peroxide: Dibenzoyl peroxide, Niper NS manufactured by Nippon Oil & Fats Co., Ltd. (1 minute half-life temperature: 133°C) Liquid polymer 1: Aromatic oil, Diana Process Oil AH-58 (molecular weight: 1000) manufactured by Idemitsu Kosan Co., Ltd. Liquid polymer 2: Paraffin oil, Kaneda Hicoll K-350 (molecular weight: 850) Liquid polymer 3: Polybutene oil, JXTG Nippon Oil & Energy Corporation's Nippon Oil Polybutene HV-15 (molecular weight: 1300)

[0058] As is clear from Tables 1-2, the adhesive sealant materials of Examples 1-5, when used as a sealant layer of a self-sealing type pneumatic tire, exhibited good sealing and adhesive properties both immediately after production and after storage under the above-mentioned conditions. That is, the sealing and adhesive properties could be maintained well for a long period of time. In addition, the flow of the sealant during driving could also be suppressed. On the other hand, the adhesive sealant materials of Comparative Examples 1-4 did not contain sulfur, so proper vulcanization was not performed, and the sealing and adhesive properties deteriorated after storage under the above-mentioned conditions. The adhesive sealant materials of Comparative Examples 5-6 had a large viscosity difference ΔV, so the sealing and adhesive properties deteriorated after storage under the above-mentioned conditions. The adhesive sealant materials of Comparative Examples 7-8 were formulated with quinone dioxime instead of sulfur, so they could not ensure adhesion both immediately after production and after storage under the above-mentioned conditions. The adhesive sealant material of Comparative Example 10 was formulated with quinone dioxime instead of sulfur, and furthermore had a large viscosity V1, so they could not ensure sealing and adhesive properties both immediately after production and after storage under the above-mentioned conditions. [Explanation of symbols]

[0059] 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 CL Tire Equator

Claims

1. An adhesive sealant material constituting a sealant layer disposed on an inner surface of a pneumatic tire, comprising: The sealant material composition is made by blending 0.1 to 40 parts by mass of sulfur, more than 0 part by mass and less than 1 part by mass of a cross-linking aid, and 50 parts by mass or more of a plasticizer component with respect to 100 parts by mass of a rubber component, the plasticizer component is selected from paraffin oil, polybutene oil, polyisobutene oil, and aromatic oil; An adhesive sealant material characterized in that a viscosity V1 measured under conditions of -20°C immediately after vulcanization is 20 kPa·s or less, and a viscosity difference ΔV between a viscosity V2 measured under conditions of -20°C after storage in a 30°C environment for two weeks immediately after vulcanization and the viscosity V1 is 5 kPa·s or less.

2. 2. The adhesive sealant according to claim 1, wherein a viscosity difference ΔV between the viscosity V1 and the viscosity V2 is 3 kPa·s or less.

3. 3. The adhesive sealant according to claim 1, wherein 1 to 40 parts by mass of an organic peroxide is blended with respect to 100 parts by mass of the rubber component.

4. 4. The adhesive sealant material according to claim 1, further comprising 10% by mass or more of butyl rubber relative to 100% by mass of the rubber component.

5. 5. The adhesive sealant according to claim 4, wherein the butyl rubber comprises a chlorinated butyl rubber, and the amount of the chlorinated butyl rubber is 5% by mass or more relative to 100% by mass of the rubber component.

6. 6. The adhesive sealant material according to claim 1, wherein the plasticizer component is paraffin oil.

7. 7. The adhesive sealant material according to claim 6, wherein the paraffin oil has a molecular weight of 800 or more.

8. 8. The adhesive sealant material according to any one of claims 1 to 7, characterized in that it is vulcanized under conditions of a vulcanization temperature of 150° C. or higher and a vulcanization time of 5 to 60 minutes.

9. A pneumatic tire comprising a sealant layer made of the adhesive sealant material according to any one of claims 1 to 8.

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