JP7397283B2 - pneumatic tires - Google Patents

Description

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

In a pneumatic tire, it has been proposed to provide a sealant layer on the inner side of an inner liner layer in the tread portion in the tire radial direction (for example, see Patent Document 1). In such pneumatic tires, when a foreign object such as a nail pierces the tread, the sealant material that makes up the sealant layer flows into the through hole, suppressing the decrease in air pressure and maintaining running. becomes possible.

In the above-mentioned self-sealing type pneumatic tires, if the viscosity of the sealant material is low, it is expected that the sealant material will more easily flow into the through-hole, improving the sealing performance, but it will also reduce the heat and centrifugal force applied during driving. If the sealant material flows toward the tire center side due to the influence, and as a result, the through hole deviates from the tire center region, there is a risk that the sealant material will be insufficient and sufficient sealing performance will not be obtained. On the other hand, if the viscosity of the sealant material is high, although the above-described flow of the sealant material can be prevented, it becomes difficult for the sealant material to flow into the through hole, and there is a possibility that the sealing performance may deteriorate. Therefore, the sealant composition constituting the sealant is required to suppress the flow of the sealant as the vehicle travels and ensure good sealing performance in a well-balanced manner.

JP2006-152110A

The purpose of the present invention is to improve the sealing properties of the sealant layer provided on the inner surface of a self-sealing type pneumatic tire, and to suppress the flow of the sealant during driving, thereby achieving both of these performances in a well-balanced manner. Our goal is to provide pneumatic tires that make it possible.

A pneumatic tire of the present invention that achieves the above object includes a tread portion extending in the circumferential direction of the tire and forming an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and a tire of the sidewall portions. A pneumatic tire comprising a pair of bead portions disposed on the inner side in the outer radial direction and having a sealant layer on the inner side in the tire radial direction of at least the inner liner layer in the tread portion, the sealant material composition constituting the sealant layer comprising: , for 100 parts by mass of a rubber component containing 80% by mass or more of butyl rubber, 5 parts by mass to 20 parts by mass of organic peroxide, 0.1 parts by mass to 40 parts by mass of crosslinking agent, more than 0 parts by mass of crosslinking aid 1 part by mass The sealant composition has a tan δ of 0.2 or more and 0.5 or less at 80°C.

The pneumatic tire of the present invention exhibits good sealing properties while suppressing the flow of the sealant during driving, since the sealant material composition constituting the sealant layer provided on the inner surface of the tire has the above-mentioned properties. can do.

In the pneumatic tire of the present invention, the tan δ of the sealant composition at 100° C. is preferably 0.25 or more and 0.5 or less. When the sealant material composition has such characteristics, it is advantageous for exhibiting good sealing properties while suppressing flow of the sealant during running.

In the pneumatic tire of the present invention, it is preferable that the difference between the tan δ of the sealant composition at 80°C and the tan δ of the rubber composition constituting the inner liner layer at 80°C is 0.1 or more and 0.3 or less. . As a result, the difference in physical properties between the sealant layer and the inner liner layer can be suppressed to an appropriate range, so that the flow of the sealant during running can be effectively suppressed.

In the pneumatic tire of the present invention, as described above, the sealant composition contains 5 parts by mass to 20 parts by mass of an organic peroxide, 5 parts by mass to 20 parts by mass of an organic peroxide, 0.1 to 40 parts by weight of the agent and more than 0 to less than 1 part by weight of the crosslinking aid are blended. Such a formulation is advantageous in imparting the above-mentioned physical properties to the sealant composition. In addition, by crosslinking using a combination of a crosslinking agent and an organic peroxide, it is possible to secure sufficient viscosity to obtain good sealing properties and to obtain appropriate elasticity that does not flow during running. It is also possible to achieve a good balance of performance.

At this time, it is preferable that the butyl rubber contains chlorinated butyl rubber, and the amount of the chlorinated butyl rubber blended is 5% by mass or more based on 100% by mass of the rubber component. By using such a blend, adhesion to the inner surface of the tire can be improved.

In the pneumatic tire of the present invention, it is preferable that the crosslinking agent blended into the sealant composition contains a sulfur component. This increases the reactivity of the rubber component (butyl rubber) with the crosslinking agent (sulfur) and organic peroxide, and improves the processability of the sealant composition.

In the pneumatic tire of the present invention, it is preferable that the amount of the crosslinking aid added to the sealant composition is 50% by mass to 400% by mass of the amount of the crosslinking agent. This improves the balance between the crosslinking agent and the crosslinking aid, suppresses thermal deterioration, and maintains good sealing properties over a long period of time.

In the pneumatic tire of the present invention, it is preferable that the crosslinking aid added to the sealant composition is a thiazole compound or a thiuram compound. Thereby, the vulcanization speed can be accelerated and productivity can be increased. On the other hand, thermal deterioration can be suppressed more than other crosslinking aids, and it is also possible to maintain good sealing properties over a long period of time.

In the pneumatic tire of the present invention, the sealant composition preferably contains 50 to 400 parts by mass of a liquid polymer based on 100 parts by mass of the rubber component. Furthermore, it is preferable that this liquid polymer is at least one selected from paraffin oil, polybutene oil, polyisoprene oil, polybutadiene oil, and aroma oil. By using a liquid polymer in this manner, the temperature dependence of the physical properties of the sealant material composition can be reduced, and the sealing performance in a low-temperature environment can also be improved. Furthermore, when the molecular weight of the liquid polymer is 800 or more, it is possible to prevent oil from transferring from the sealant layer provided on the inner surface of the tire to the tire body and affecting the tire.

1 is a meridian cross-sectional view showing an example of a pneumatic tire of the present invention.

Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

The pneumatic tire (self-sealing type pneumatic tire) of the present invention, as shown in FIG. The tire includes a pair of sidewall portions 2 and a pair of bead portions 3 disposed on the inner side of the sidewall portion 2 in the tire radial direction. In FIG. 1, the symbol CL indicates the tire equator. Although not depicted in FIG. 1 because it is a meridian cross-sectional view, the tread portion 1, sidewall portion 2, and bead portion 3 each extend in the circumferential direction of the tire and form an annular shape. A toroidal basic structure is constructed. In addition, other tire constituent members in the meridian cross-sectional view also extend in the tire circumferential direction to form an annular shape unless otherwise specified.

In the example of FIG. 1, a carcass layer 4 is mounted 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 of the vehicle to the outside around the bead core 5 and bead filler 6 arranged in each bead portion 3. The bead filler 6 is arranged on the outer peripheral side of the bead core 5 and is wrapped by the main body part and the folded part of the carcass layer.

A plurality of belt layers 7 (two layers in FIG. 1) are embedded in the outer peripheral side of the carcass layer 4 in the tread portion 1. Among these multiple belt layers 7, the layer with the smallest belt width is called the smallest belt layer 7a, and the layer with the largest belt width is called the largest belt layer 7b. Each belt layer 7 includes a plurality of reinforcing cords that are inclined with respect to the tire circumferential direction, and the reinforcing cords are arranged so as to 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, for example, in the range of 10° to 40°. A belt reinforcing layer 8 is provided on the outer peripheral side of the belt layer 7 in the tread portion 1 . In the illustrated example, two belt reinforcing layers 8 are provided: a full cover layer that covers the entire width of the belt layer 7, and an edge cover layer that is disposed on the outer peripheral side of the full cover layer and covers only the ends of the belt layer 7. ing. 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°.

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

As shown in FIG. 1, a sealant layer 10 is provided on the inner side of the inner liner layer 9 in the tire radial direction in the tread portion 1. In particular, the sealant layer 10 is provided on the inner surface of the tire corresponding to a region where a foreign object such as a nail may be stuck during running, that is, a ground contact region of the tread portion 1. In particular, it is preferable to provide the sealant layer 10 in a wider range than the width of the minimum belt layer 7a. The sealant composition of the present invention is used for this sealant layer 10. The sealant layer 10 is applied to the inner surface of the pneumatic tire having the basic structure described above, and when a foreign object such as a nail pierces the tread portion 1, the sealant layer 10 is formed in the through hole. The sealant material flows in and seals the through hole, thereby suppressing a decrease in air pressure and making it possible to maintain running.

The sealant layer 10 has a thickness of, for example, 0.5 mm to 5.0 mm. By having a thickness of this extent, it is possible to suppress the flow of the sealant during traveling while ensuring good sealing performance. Further, the processability when applying the sealant layer 10 to the inner surface of the tire is also improved. If the thickness of the sealant layer 10 is less than 0.5 mm, it will be difficult to ensure sufficient sealing performance. If the thickness of the sealant layer 10 exceeds 5.0 mm, the weight of the tire increases and rolling resistance deteriorates. Note that the thickness of the sealant layer 10 is an average thickness.

The sealant layer 10 can be formed by later applying it to the inner surface of a vulcanized pneumatic tire. For example, a sealant material made of the sealant composition described below and molded into a sheet shape is pasted all around the inner surface of the tire, or a sealant material made of the sealant composition described below and molded into a string or band shape is applied to the entire circumference of the inner surface of the tire. The sealant layer 10 can be formed by pasting it spirally on the inner surface of the tire. Moreover, at that time, by heating the sealant material composition, variations in performance of the sealant material composition can be suppressed. As for the heating conditions, the temperature is preferably 140° C. to 180° C., more preferably 160° C. to 180° C., and the heating time is preferably 5 minutes to 30 minutes, more preferably 10 minutes to 20 minutes. According to this method for manufacturing a pneumatic tire, it is possible to efficiently manufacture a pneumatic tire that has good sealing performance in the event of a puncture and in which flow of sealant is difficult to occur.

Since the present invention mainly relates to a sealant composition used for 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 similar to those described above. but not limited to.

The sealant material composition constituting the sealant layer 10 of the pneumatic tire of the present invention has a tan δ at 80°C (hereinafter referred to as "tan δ (80°C)") of 0.2 or more and 0.5 or less, preferably 0.35. ~0.45. When the sealant material composition has such characteristics, it is possible to exhibit good sealing properties while suppressing flow of the sealant during running. If the tan δ (80° C.) of the sealant composition is less than 0.2, the effect of improving sealing performance cannot be sufficiently achieved. If the tan δ (80° C.) of the sealant composition exceeds 0.5, the flow of the sealant cannot be sufficiently suppressed. Note that tan δ (80°C) is measured using a viscoelastic spectrometer in accordance with JIS K6394 under conditions of an elongation strain rate of 10% ± 2%, a frequency of 20 Hz, and a temperature of 80°C.

Furthermore, the sealant composition preferably has a tan δ at 100°C (hereinafter referred to as "tan δ (100°C)") of preferably 0.25 or more and 0.5 or less, more preferably 0.3 to 0.4. . When the sealant material composition has such characteristics, it is advantageous for exhibiting good sealing properties while suppressing flow of the sealant during running. If the tan δ (100° C.) of the sealant composition is less than 0.25, further improvement in sealing performance cannot be expected. When the tan δ (100° C.) of the sealant composition exceeds 0.5, the effect of suppressing the flow of the sealant becomes limited. Note that tan δ (100°C) is measured using a viscoelastic spectrometer in accordance with JIS K6394 under the conditions of an elongation strain rate of 10% ± 2%, a frequency of 20 Hz, and a temperature of 100°C.

From the viewpoint of fluidity of the sealant, it is preferable that the tan δ (80° C.) of the sealant material composition is appropriately larger than that of the rubber composition constituting the inner liner layer 9 adjacent to the sealant layer 10. Specifically, the difference between the tan δ (80°C) of the sealant composition and the tan δ (80°C) of the rubber composition constituting the inner liner layer is preferably 0.1 or more and 0.3 or less, more preferably 0. It is good if it is between .1 and 0.2. Further, the difference between the tan δ (100° C.) of the sealant composition and the tan δ (100° C.) of the rubber composition constituting the inner liner layer is preferably 0.1 to 0.2. As a result, the difference in physical properties between the sealant layer 10 and the inner liner layer 9 can be suppressed to an appropriate range, so that the flow of the sealant during running can be effectively suppressed. If the difference in tan δ (80°C) is less than 0.1, the difference in tan δ (80°C) is substantially eliminated, and the desired effect cannot be sufficiently obtained. If the difference in tan δ (80° C.) exceeds 0.3, the effect of suppressing the difference in physical properties and suppressing the flow of the sealant cannot be sufficiently expected.

The specific formulation of the sealant composition used in the present invention is not particularly limited as long as it has the above-mentioned physical properties. However, in order to reliably obtain the above-mentioned physical properties, it is preferable to employ, for example, the formulation described below.

In the sealant composition of the present invention, it is preferable that halogenated butyl rubber is included as the butyl rubber. Examples of the 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 proportion of chlorinated butyl rubber in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass to 85% by mass. Including halogenated butyl rubber (chlorinated butyl rubber) increases the reactivity of the rubber component with the crosslinking agent and organic peroxide described below, which is advantageous in achieving both sealing performance and suppressing sealant flow. Become. Further, the processability of the sealant composition can also be improved. If the proportion of chlorinated butyl rubber is less than 5% by mass, the reactivity between the rubber component and the crosslinking agent or organic peroxide described below will not be sufficiently improved, and the desired effect will not be sufficiently obtained.

In the sealant composition of the present invention, the entire amount of butyl 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 the non-halogenated butyl rubber include unmodified butyl rubber commonly used in sealant compositions, such as BUTYL-065 manufactured by JSR Corporation and BUTYL-301 manufactured by LANXESS Corporation. When halogenated butyl rubber and non-halogenated butyl rubber are used together, 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.

In the sealant composition of the present invention, it is preferable to use two or more types of butyl rubber in combination. That is, it is preferable to use chlorinated butyl rubber in combination with other halogenated butyl rubber (for example, brominated butyl rubber) or non-halogenated butyl rubber. Chlorinated butyl rubber, other halogenated butyl rubber (brominated butyl rubber), and non-halogenated butyl rubber have different vulcanization rates, so if at least two types are used in combination, the The physical properties (viscosity, elasticity, etc.) of the sealant composition after vulcanization are not uniform. That is, due to the distribution of rubbers having different vulcanization rates (variations in concentration) within the sealant composition, relatively hard portions and relatively soft portions coexist in the sealant layer after vulcanization. As a result, fluidity is suppressed in the relatively hard portions, and sealing performance is exhibited in the relatively soft portions, which is advantageous in achieving both these performances in a well-balanced manner.

In the sealant composition of the present invention, diene rubbers other than butyl rubber can also be blended as the rubber component. Other diene rubbers include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), styrene isoprene butadiene rubber (SIBR), ethylene propylene diene rubber (EPDM), and chloroprene rubber. Rubbers commonly used in sealant compositions, such as rubber (CR) and acrylonitrile butadiene rubber (NBR), can be used. These other diene rubbers can be used alone or in any blend.

In the sealant composition of the present invention, it is preferable to mix a crosslinking agent and an organic peroxide. Note that the "crosslinking agent" in the present invention refers to a crosslinking agent other than organic peroxides, and examples thereof include sulfur, zinc white, cyclic sulfide, resin (resin vulcanization), amine (amine vulcanization), etc. be able to. As the crosslinking agent, it is particularly preferable to use one containing a sulfur component (for example, sulfur). By blending a crosslinking agent and an organic peroxide in combination in this way, it is possible to achieve appropriate crosslinking to ensure both sealing performance and prevention of flow of the sealant. The blending amount of the crosslinking agent is preferably 0.1 parts by mass to 40 parts by mass, more preferably 0.5 parts by mass to 10 parts by mass, based on 100 parts by mass of the above-mentioned rubber component. Further, the amount of organic peroxide to be blended is preferably 5 parts by mass to 20 parts by mass, more preferably 10 parts by mass to 15 parts by mass, based on 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 equivalent to substantially not including the crosslinking agent, and appropriate crosslinking cannot be performed. If the amount of the crosslinking agent exceeds 40 parts by mass, crosslinking of the sealant composition will proceed too much and the sealing performance will deteriorate. If the amount of organic peroxide is less than 5 parts by mass, the amount of organic peroxide is too small and sufficient crosslinking cannot be achieved, making it impossible to obtain desired physical properties. If the amount of organic peroxide exceeds 20 parts by mass, crosslinking of the sealant composition will proceed too much and the sealing performance will deteriorate.

When using a crosslinking agent and an organic peroxide together in this way, the mass ratio A/B of the amount A of the crosslinking agent and the amount B of the organic peroxide is preferably 5/1 to 1/200, More preferably, it is 1/10 to 1/20. With such a blending ratio, it is possible to achieve a better balance between ensuring sealing performance and preventing flow of the sealant.

Examples of organic peroxides include dicumyl peroxide, t-butylcumyl peroxide, benzoyl peroxide, dibenzoyl peroxide, butyl hydroperoxide, p-chlorobenzoyl peroxide, 1,1,3,3- Examples include tetramethylbutyl hydroperoxide. In particular, organic peroxides having a 1-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 addition, in the present invention, the "1-minute half-life temperature" generally adopts the value listed in the "Organic Peroxide Catalog 10th Edition" by NOF Corporation, and if it is not listed, the value listed in the catalog is used. Similar to the method described above, the value obtained from thermal decomposition in an organic solvent is used.

It is preferable to blend a crosslinking aid into the sealant composition of the present invention. A crosslinking aid is a compound that acts as a crosslinking reaction catalyst when mixed with a crosslinking agent containing a sulfur component. By blending a crosslinking agent and a crosslinking aid, the vulcanization rate can be accelerated and the productivity of the sealant composition can be increased. The amount of the crosslinking aid to be blended is preferably more than 0 part by weight and less than 1 part by weight, more preferably 0.1 part by weight to 0.9 part by weight, based on 100 parts by weight of the above-mentioned rubber component. By suppressing the blending amount of the crosslinking aid in this manner, it is possible to suppress deterioration (thermal deterioration) of the sealant composition while promoting the crosslinking reaction as a catalyst. When the amount of the crosslinking aid is 1 part by mass or more, the effect of suppressing thermal deterioration cannot be sufficiently obtained. Furthermore, as mentioned above, the crosslinking aid acts as a crosslinking reaction catalyst when combined with a crosslinking agent containing a sulfur component, so even if it is coexisting with an organic peroxide instead of a sulfur component, it will not act as a crosslinking reaction catalyst. Therefore, a large amount of crosslinking aid must be used, which accelerates thermal deterioration.

The amount of the crosslinking aid is preferably 50% to 400% by weight, more preferably 100% to 200% by weight of the amount of the above-mentioned crosslinking agent. By appropriately blending the crosslinking aid with the crosslinking agent in this way, the crosslinking aid can perform its catalytic function well, ensuring both sealing performance and prevention of sealant flow. It will be advantageous for If the amount of the crosslinking aid is less than 50% by mass of the amount of the crosslinking agent, fluidity will decrease. If the amount of the crosslinking aid exceeds 400% by mass of the amount of the crosslinking agent, the deterioration resistance will decrease.

Examples of crosslinking aids include sulfenamide-based, thiazole-based, thiuram-based, thiourea-based, guanidine-based, dithiocarbamate-based, aldehyde-amine-based, aldehyde-ammonia-based, imidazoline-based, xanthate-based compounds ( vulcanization accelerator). Among these, thiazole-based, thiuram-based, guanidine-based, and dithiocarbamate-based vulcanization accelerators can be suitably used. Examples of thiazole-based vulcanization accelerators include 2-mercaptobenzothiazole and dibenzothiazyl disulfide. Examples of thiuram-based vulcanization accelerators include tetramethylthiuram monosulfide and tetramethylthiuram disulfide. Examples of the guanidine-based vulcanization accelerator include diphenylguanidine and di-orthotolylguanidine. Examples of dithiocarbamate-based vulcanization accelerators include sodium dimethyldithiocarbamate and sodium diethyldithiocarbamate. In particular, in the present invention, it is preferable to use a thiazole-based or thiuram-based vulcanization accelerator, which can suppress variations in performance of the resulting sealant composition.

Note that a compound that actually functions as a crosslinking agent, such as quinone dioxime, is sometimes referred to as a crosslinking aid for convenience, but the crosslinking aid in the present invention is a catalyst for the crosslinking reaction by the crosslinking agent, as described above. Since quinone dioxime is a compound that functions as a crosslinking agent, it does not fall under the category of crosslinking auxiliary agent in the present invention.

The sealant composition of the present invention preferably contains a liquid polymer. By blending the liquid polymer in this way, the viscosity of the sealant composition can be increased and the sealing performance can be improved. The amount of the liquid polymer to be blended is preferably 50 parts by mass to 400 parts by mass, more preferably 70 parts by mass to 200 parts by mass, based on 100 parts by mass of the above-mentioned 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 achieved. If the amount of the liquid polymer exceeds 400 parts by mass, flow of the sealant cannot be sufficiently prevented.

The liquid polymer is preferably capable of co-crosslinking with the rubber component (butyl rubber) in the sealant composition, such as paraffin oil, polybutene oil, polyisoprene oil, polybutadiene oil, polyisobutene oil, aroma oil, polypropylene glycol, etc. can be mentioned. Among these, paraffin oil, polybutene oil, polyisoprene oil, polybutadiene oil, aromatic oil, and polypropylene are used in order to suppress the temperature dependence of the physical properties of the sealant composition and ensure good sealing properties in low-temperature environments. Glycols are preferred, and paraffin oil is particularly preferred. Further, the molecular weight of the liquid polymer is preferably 800 or more, more preferably 1000 or more, and even more preferably 1200 or more and 3000 or less. By using a material with such a large molecular weight, it is possible to prevent the oil component from migrating from the sealant layer provided on the inner surface of the tire to the tire body and affecting the tire.

The sealant composition composed of the above-mentioned formulation contains at least butyl rubber to give the rubber component a moderately high viscosity, while crosslinking is performed using a combination of a crosslinking agent and an organic peroxide. It is possible to achieve both of these performances in a well-balanced manner by ensuring sufficient viscosity to obtain a good sealing performance while also obtaining appropriate elasticity that does not flow during running. Furthermore, when the butyl rubber and the organic peroxide are blended in appropriate amounts as described above, the physical properties of the sealant composition (tan δ (80°C) and tan δ (100°C)) and the properties with the inner liner layer 9 are improved. The effect of setting gender differences within an appropriate range can also be expected. Therefore, it can be suitably used for the sealant layer 10 (sealant material) of self-sealing type pneumatic tires, and it achieves a good balance between suppressing flow and improving sealing performance while fully demonstrating the basic performance as a sealant material. It becomes possible to do so.

EXAMPLES Hereinafter, the present invention will be further explained with reference to Examples, but the scope of the present invention is not limited to these Examples.

A sealant material composition constituting the sealant layer in a pneumatic tire having a tire size of 255/40R20, having the basic structure shown in FIG. 1, and having a sealant layer made of a sealant on the inner side of the inner liner layer in the tread portion in the tire radial direction. Tires of Comparative Examples 1 to 5 and Examples 1 to 11 were manufactured in which the formulation and physical properties were set as shown in Tables 1 to 2. Examples 4, 7, and 10 are reference examples) .

In the pneumatic tire, either an inner liner layer having a tan δ (80° C.) of 0.20 or an inner liner layer having a tan δ (80° C.) 0.10 was used. In Tables 1 and 2, the former is indicated as "A" and the latter as "B", and tan δ (80° C.) is also indicated. In addition, the difference in tan δ (80°C) between the sealant composition and the rubber composition constituting the inner liner layer (the value obtained by subtracting the tan δ (80°C) of the inner liner layer from the tan δ (80°C) of the sealant composition) ) are also shown.

The tan δ at 80°C (“tan δ (80°C)” in the table) and the tan δ at 100°C (“tan δ (100°C)” in the table) are the viscoelasticity manufactured by Toyo Seiki Seisakusho Co., Ltd. in accordance with JIS K6394. These values were measured using a spectrometer under the conditions of an elongation strain rate of 10%±2%, a vibration frequency of 20 Hz, and a temperature of 80° C. or 100° C.

These test tires were evaluated for sealing performance and sealant fluidity using the following test methods, and the results are also shown in Tables 1 and 2.

Sealing performance Each test tire was assembled to a wheel with a rim size of 20 x 9J and mounted on a test vehicle, and a nail with a diameter of 4.0 mm was driven into the tread under conditions of an initial air pressure of 250 kPa and a load of 8.5 kN. The air pressure was measured after the tire was left undisturbed for 1 hour. The evaluation results were shown in the following five stages. It should be noted that if the score of the evaluation result is "2" or more, sufficient sealing performance was exhibited, and a higher score means that more excellent sealing performance was exhibited.
5: The air pressure after standing is 240 kPa or more and 250 kPa or less 4: The air pressure after standing is 230 kPa or more and less than 240 kPa 3: The air pressure after standing is 215 kPa or more and less than 230 kPa 2: The air pressure after standing is 200 kPa or more and Less than 215kPa 1: Air pressure after standing still is less than 200kPa

Fluidity of sealant The test tire was assembled onto a wheel with a rim size of 20 x 9J, mounted on a drum testing machine, and run for 1 hour at an air pressure of 220kPa, a load of 8.5kN, and a running speed of 80km/h. I checked the condition. The evaluation results are determined by drawing lines of 20 x 40 squares with 5 mm squares on the surface of the sealant layer before running, and counting the number of squares whose shape is distorted after running.If no sealant flow is observed (distorted squares), If the number of distorted squares is 0, it is indicated by "○", if the number of distorted squares is less than 1/4 of the total, it is indicated by "△", and if the number of distorted squares is 1/4 or more of the total, it is indicated by "△". are indicated with an "x".

The types of raw materials used in Tables 1 and 2 are shown below.
・Butyl rubber 1: Chlorinated butyl rubber, CHLOROBUTYL1066 manufactured by JSR Corporation
・Butyl rubber 2: Brominated butyl rubber, BROMOBUTYL2222 manufactured by JSR Corporation
・Natural rubber: Natural rubber manufactured by SRI TRANG ・Organic peroxide: Dibenzoyl peroxide, Niper NS manufactured by NOF Corporation (1 minute half-life temperature: 133°C)
・Crosslinking agent 1: Sulfur, small lump sulfur manufactured by Hosoi Chemical Industry Co., Ltd. ・Crosslinking agent 2: Quinone dioxime, Balnock GM manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
・Crosslinking aid: Thiazole vulcanization accelerator, Noxela MZ manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
・Liquid polymer: Paraffin oil, Kaneda Hycor K-350 (molecular weight: 850)

As is clear from Tables 1 and 2, the pneumatic tires of Examples 1 to 11 exhibited good fluidity and good sealing properties both at room temperature and in low-temperature environments, and balanced these performances. It was a good balance. On the other hand, in Comparative Examples 1 to 5, at least one of sealing performance and fluidity deteriorated, and it was not possible to achieve both of these performances.

1 Tread portion 2 Sidewall portion 3 Bead portion 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 (10)

A tread portion extending in the circumferential direction of the tire and forming an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on the inner side of the sidewall portions in the outer diameter direction of the tire. A pneumatic tire comprising: a sealant layer on the inside of the inner liner layer in at least the tread portion in the tire radial direction;
The sealant material composition constituting the sealant layer contains 5 to 20 parts by mass of an organic peroxide and 0.1 to 40 parts by mass of a crosslinking agent per 100 parts by mass of a rubber component containing 80% by mass or more of butyl rubber. 1. A pneumatic tire, characterized in that the sealant composition contains more than 0 parts by mass and less than 1 part by mass of a crosslinking aid, and has a tan δ of 0.2 or more and 0.5 or less at 80°C. The pneumatic tire according to claim 1, wherein tan δ at 100° C. of the sealant composition is 0.25 or more and 0.5 or less. Claim 1 or 2, wherein the difference between the tan δ of the sealant composition at 80°C and the tan δ of the rubber composition constituting the inner liner layer at 80°C is 0.1 or more and 0.3 or less. Pneumatic tires listed in. The pneumatic tire according to any one of claims 1 to 3, wherein the butyl rubber contains chlorinated butyl rubber, and the amount of the chlorinated butyl rubber blended is 5% by mass or more based on 100% by mass of the rubber component. The pneumatic tire according to any one of claims 1 to 4, wherein the crosslinking agent contains a sulfur component. The pneumatic tire according to any one of claims 1 to 5 , wherein the amount of the crosslinking aid is 50% to 400% by weight of the amount of the crosslinking agent. The pneumatic tire according to any one of claims 1 to 6, wherein the crosslinking aid is a thiazole compound or a thiuram compound. The pneumatic tire according to any one of claims 1 to 7 , wherein 50 to 400 parts by mass of the liquid polymer is blended with 100 parts by mass of the rubber component. The pneumatic tire according to claim 8 , wherein the liquid polymer is at least one selected from paraffin oil, polybutene oil, polyisoprene oil, polybutadiene oil, and aroma oil. The pneumatic tire according to claim 8 or 9, wherein the liquid polymer has a molecular weight of 800 or more.

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