JP2002144827A - Safety tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a safety tire capable of stable travel and excellent in run flat durability even after the tire is damaged without sacrificing rolling resistance and comfortableness performance at ordinary travel time. SOLUTION: This safety tire is provided with a carcass layer, a tread part arranged on the tire radial directional outside of the carcass slayer, and a pair of side parts arranged on the left and right of the tread part, and is characterized by arranging a rubber member being 75% or more of a dynatic storage elastic modulus at 50 deg.C on a minimum value of a dynamic storage elastic modulus at 200 to 250 deg.C in the side parts.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a safety tire which is not affected by a puncture caused by an injury or the like, in particular, durability (run-flat durability) in running after a tire is damaged and vibration riding comfort in normal running (ride comfort). The present invention relates to safety tires having excellent properties.

[0002]

2. Description of the Related Art In general, pneumatic tires contain air inside the tire, maintain a vacuum-based absolute pressure (hereinafter, simply referred to as an internal pressure) of about 200 to 400 kPa, and maintain a tire carcass and belt. A tension is generated in the tire skeleton, and the tension enables the tire to be deformed and restored in response to an input to the tire. That is, by maintaining the internal pressure of the tire in a predetermined range, a constant tension is generated in the skeleton of the tire to provide a load supporting function and increase rigidity, such as driving, braking and turning performance. It provides the basic performance required for running the vehicle. By the way, when the tire held at the predetermined internal pressure is damaged, air leaks out to the outside through the wound and the tire internal pressure decreases to the atmospheric pressure, resulting in a so-called puncture state. Most of the tension that was being applied will be lost. For this reason, a load supporting function obtained by applying a predetermined internal pressure to the tire, and driving, braking and turning performance are also lost,
The vehicle equipped with the tires becomes unable to run.

[0003] Therefore, many proposals have conventionally been made on safety tires that can run even in a punctured state. For example, various types of pneumatic safety tires for automobiles have been proposed, such as those having a double wall structure, those having a load supporting device disposed in the tire, and those having reinforced tire side portions. . Among these proposals, as a technology actually used, there is a tire provided with a side reinforcing layer made of relatively hard rubber on an inner surface from a shoulder portion to a bead portion around a sidewall portion of the tire, This kind of tire mainly has an aspect ratio of 60
% Or less, so-called run flat tires. However, the means of adding the side reinforcing layer increases the tire weight by 30 to 40% and increases the longitudinal spring constant and the front and rear spring constant of the tire, so that the rolling resistance is significantly deteriorated and the normal internal pressure running before puncturing is performed. However, there is a disadvantage that the ride comfort is deteriorated. Further, there is a disadvantage that the burden on the vehicle suspension is large, and the durability of the vehicle suspension mechanism is greatly reduced. Therefore, normal driving performance, vehicle durability,
It is a technology that is still versatile because it has a negative effect on fuel economy and the environment.

On the other hand, the tire has a high section height and an aspect ratio of 6
For pneumatic tires of 0% or more, in order to avoid heat generation of the sidewall portion due to relatively high speed and long distance running, an internal support such as a core is arranged on a rim to support a load at the time of puncturing. Run flat tires are mainly applied. However, the tire cannot withstand local repeated input generated between the tire and the internal support during run flat after puncture, and as a result, the mileage after puncture is generally about 100 to 200 km. Was limited to. In addition, the operation of assembling the tire to the rim after disposing the internal support inside the tire has been a problem in that it is complicated and takes a long time. In this regard, there has been proposed a device in which a difference is provided in the rim diameter between the one end side and the other end side in the width direction of the rim so that the internal support can be easily inserted, but a sufficient effect has not been obtained. In order to extend the running distance after a puncture of a run flat tire having an internal support, it is effective to add a skeleton material to make the tire structure heavier, but the additional skeleton material is used during normal use. It is not practical to employ this method because the rolling resistance and ride comfort of the vehicle deteriorate.

Further, a tire in which the internal cavity of an assembly of a tire and a rim to be attached to the tire is filled with a foam of closed cells is disclosed in, for example, JP-A-6-127207 and JP-A-6-127207.
183226, JP-A-7-186610 and JP-A-8-332805. The tires proposed for these are mainly agricultural tires,
It is limited to special or small tires such as rally tires, two-wheeled vehicle tires and bicycle tires. Therefore, its application to tires for passenger cars, tires for trucks and buses and the like, in particular, for tires in which rolling resistance and ride comfort are emphasized, has not been known. In any of the foams, since the inside of the closed cells is at atmospheric pressure, it was not functionally sufficient to substitute high-pressure air in a normal tire.

[0006] Further, Japanese Patent No. 2987076 discloses a puncture-free tire having a foam filler inserted into the inner peripheral portion thereof. Is urethane-based, so that the energy loss due to the intermolecular hydrogen bonding of the urethane group is large and the self-heating property is high. Therefore, when the urethane foam is filled in the tire, the foam is heated by repeated deformation during rolling of the tire, and the durability is greatly reduced. In addition, since a material that is difficult to form bubbles independently is used, the bubbles are easily communicated, and it is difficult to retain gas. Particularly, in running after tire damage, there is a disadvantage that a desired tire internal pressure cannot be maintained. .

[0007]

SUMMARY OF THE INVENTION The present invention enables stable running under such circumstances without sacrificing rolling resistance and riding comfort during normal running, even after tire damage. It is an object of the present invention to provide a safety tire having excellent run flat durability.

[0008]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and found that both of the vibration riding comfort performance at the time of normal driving under internal pressure and the run flat performance at the time of puncturing are compatible. It is effective to place a rubber member on the side part that has the function of suppressing the decrease in elastic modulus at ultra-high temperatures and the function of low elastic modulus at low temperatures and the function of significantly increasing the elastic modulus at ultra-high temperatures. I found That is, the present invention comprises a carcass layer, a tread portion disposed radially outside the carcass layer, and a pair of side portions disposed on the left and right sides of the tread portion. , The minimum value of the dynamic storage modulus at 200 to 250 ° C. is
It is intended to provide a safety tire characterized by disposing a rubber member having a dynamic storage modulus at 50 ° C. of 75% or more. Further, the present invention comprises a carcass layer, a tread portion disposed radially outward of the carcass layer, and a pair of side portions disposed on the left and right of the tread portion. Dynamic storage modulus at 50 ° C is 2
-20 MPa and the minimum value of the dynamic storage modulus at 200-250 ° C. is 7
It is an object of the present invention to provide a method for achieving a balance between the vibration riding comfort performance and the run-flat durability performance when the pneumatic tire is used under normal driving by using a rubber member that is at least 5% when the internal pressure is applied. Furthermore, the present invention comprises a carcass layer, a tread portion disposed radially outside the carcass layer in the tire radial direction, and a pair of side portions disposed on the left and right of the tread portion. A rubber member having a dynamic storage modulus at 50 ° C. of 2 to 20 MPa and a minimum value of the dynamic storage modulus at 200 to 250 ° C. equal to or more than the dynamic storage modulus at 50 ° C. By arranging the pneumatic tires, there is also provided a method for achieving both the vibration riding comfort performance and the run-flat durability performance when using the pneumatic tire at the time of internal pressure and normal running.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a rubber member having a function of suppressing a decrease in elastic modulus at an ultra-high temperature or an elastic modulus at an ultra-high temperature is low and the elastic modulus at an ultra-high temperature is remarkably increased. By arranging the rubber member having the function of performing the operation, it is possible to achieve a high level of both the vibration riding comfort performance and the run-flat durability performance at the time of the normal driving use under the internal pressure. That is, in the safety tire of the present invention, as the rubber member disposed on the side portion, 200 to 250
It is necessary that the minimum value of the dynamic storage modulus at 50 ° C. is 75% or more of the dynamic storage modulus at 50 ° C. 200 ~
If the minimum value of the dynamic storage modulus at 250 ° C. is less than 75% of the dynamic storage modulus at 50 ° C., it is possible to obtain both good vibration riding comfort performance and run-flat durability performance. Can not. The minimum value of the dynamic storage modulus at 200 to 250 ° C. of the rubber member is preferably 85% or more, more preferably equal to (100%) or more with respect to the dynamic storage modulus at 50 ° C. It is preferable that the minimum value of the dynamic storage modulus at -250 ° C is higher than the dynamic storage modulus at 50 ° C by 10% or more, especially 20% or more.

In the present invention, in order to obtain a rubber member having the above specific dynamic storage modulus disposed on the tire side portion, (1) the amount of vinyl bond in the conjugated diene unit is 25% As described above, the weight-average molecular weight (Mw) is 200,000 to 900,000, and the molecular weight distribution (Mw) represented by the ratio of the weight-average molecular weight to the number-average molecular weight (Mn).
(w / Mn) is 1 to 4, or (2) Mw is 200,000 to 900,000 and (Mw / M
Preferred is a conjugated diene-based polymer in which n) is 1 to 4 and has a tin atom and / or a nitrogen atom in the molecule. In the conjugated diene-based polymer of the rubber component (1), if the vinyl bond amount of the conjugated diene unit is less than 25%, 150
This is because the effect of suppressing the decrease in the elastic modulus due to the temperature rise cannot be sufficiently expected because the decrease in the elastic modulus due to the sulfur cross-linking cleavage at a high temperature of not less than ℃ is dominant. From this point, the vinyl bond amount is preferably 30% or more, and more preferably 3% or more.
5% or more is preferable. Particularly, it is preferably 40 to 60%.

The conjugated diene polymer of the rubber component (1) or (2) has a weight average molecular weight (Mw) of 20.
If it is less than 10,000, the tensile properties and rolling resistance of the rubber composition are inferior, and if it exceeds 900,000, the processability tends to be inferior. In this respect, Mw is preferably 300,000 to 800,000, and particularly 300,000 to 800,000.
700,000 is preferred. Furthermore, as for the molecular weight distribution (Mw / Mn) of the polymer, when Mw / Mn exceeds 4, the heat build-up tends to decrease, and it tends to be difficult to maintain the elastic modulus in a temperature region of 150 ° C. or higher. In this respect, Mw / Mn is preferably 1 to 3. Among the above conjugated diene-based polymers, the vinyl bond amount in the conjugated diene unit is particularly 25% or more, and the weight average molecular weight (Mw) is 200,000 or more.
900,000 and the weight average molecular weight and number average molecular weight (M
n) a molecular weight distribution (Mw / Mn) represented by the ratio of 1 to 4
And a conjugated diene polymer having a tin atom and / or a nitrogen atom in the molecule.

The conjugated diene-based polymer used for the side rubber member in the present invention is preferably a conjugated diene homopolymer and / or a conjugated diene-aromatic vinyl copolymer, and also includes these modified polymers. It is. Here, as the conjugated diene monomer, for example, 1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene and the like can be mentioned, and among them, 1,3-butadiene is preferable.
Examples of the aromatic vinyl monomer used for copolymerization with a conjugated diene monomer include styrene, α-methylstyrene, 1-vinylnaphthalene, 3-vinyltoluene,
Ethyl vinyl benzene, divinyl benzene, 4-cyclohexyl styrene, 2,2, 6-tolyl styrene and the like can be mentioned, among which styrene is preferable.

The conjugated diene polymer can be produced by various methods, and the polymerization method may be either a batch polymerization method or a continuous polymerization method. Preferred manufacturing methods are as follows. That is, it is obtained by polymerizing a monomer containing a conjugated diene in an inert solvent, preferably a hydrocarbon solvent, in the presence of an initiator such as an organic metal, preferably an organic lithium compound initiator. The hydrocarbon solvent is not particularly limited, but includes, for example, n-pentane, n-hexane, n-heptane, cyclohexane, benzene, toluene, and the like. Preferred solvents are cyclohexane and n-hexane. These hydrocarbon solvents may be used alone or as a mixture of two or more. As the organic lithium used as the initiator, a hydrocarbon lithium compound having at least one lithium atom bonded and having 2 to 20 carbon atoms is preferable. For example, n-butyllithium, ethyllithium, n-propyllithium, tert -Octyllithium, phenyllithium, etc., and preferred is n-butyllithium. These organic lithium initiators may be used alone or as a mixture of two or more. The amount of vinyl bond may be ditetrahydrofurylpropane, tetrahydrofuran, diethyl ether, dimethoxybenzene, dimethoxyethane, ethylene glycol dibutyl ether, triethylamine, pyridine, N, N, N ', N'-tetramethylethylenediamine, dipiperidinoethane, etc. By adding an appropriate amount of the ether and / or tertiary amine compound to the polymerization system, it can be changed as appropriate.

Further, the conjugated diene polymer used in the present invention includes a tin atom and / or
Alternatively, a modified polymer containing a nitrogen atom can be used.
The modified polymer in which a tin atom, a nitrogen atom, or the like is introduced into the molecular chain is preferable because it can suppress a decrease in elastic modulus due to a rise in temperature and can also suppress heat generation in a carbon black-containing rubber composition. Those having a branched structure obtained by using a functional modifier are preferred. The modified polymer is produced by a known method,
It is usually obtained by initiating polymerization with an organic lithium initiator and adding various modifiers to a solution of a polymer having a lithium active terminal (JP-B-6-89183, JP-A-11-29659, etc.). . For example,
The tin atom is introduced by a tin compound such as tin tetrachloride, tributyltin, dioctyltin dichloride, dibutyltin dichloride, triphenyltin chloride, and the nitrogen atom is an isocyanate compound such as diisocyanatodiphenylmethane, 4- (dimethylamino) benzophenone , And nitrogen-containing compounds such as 4-dimethylaminobenzylideneaniline, dimethylimidazolidinone, and N-methylpyrrolidone.

Further, by polymerizing using a lithium amide initiator obtained from a secondary amino compound such as diethylamine or an imine compound such as hexamethyleneimine and an organic lithium compound, or
The modified polymer can also be obtained by further adding the modifying agent to a solution of the polymer having a lithium active terminal obtained by the polymerization. Further, the conjugated diene-based polymer in the present invention is preferably a conjugated diene homopolymer, a conjugated diene copolymer or a conjugated diene-aromatic vinyl copolymer, and particularly, polybutadiene and styrene-butadiene copolymer, Among them, polybutadiene is preferred. Further, polymers obtained by modifying the above, particularly those having a branched structure are preferable.

The conjugated diene-based polymer may be used alone as a rubber component of the rubber member, or may be used as a mixture with another rubber. And more preferably 60% by weight or more. If it is less than 50% by weight, a decrease in rubber elasticity due to an increase in temperature may not be suppressed. In this respect, the conjugated diene-based polymer is preferably contained in an amount of 80% by weight or more, and more preferably 100% by weight. In the rubber member used in the present invention, other rubber components that can be mixed with the conjugated diene-based polymer are not particularly limited. For example, natural rubber, polyisoprene synthetic rubber (I
R); cis-1,4-polybutadiene rubber (BR), styrene-butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (C
R), butyl rubber (IIR) and the like. These rubbers may be used in combination of two or more.

Further, the composition of the rubber member includes:
As the heat resistance improver, a general formula (I) R ¹ -SSSASR ² (I) wherein A is an alkylene group having 2 to 10 carbon atoms, R ¹ and R ²
Each independently represents a monovalent organic group containing a nitrogen atom. ), At least one compound selected from citraconimide compounds and acrylate compounds. These heat resistance improvers have a minimum value of the dynamic storage elastic modulus particularly at 200 to 250 ° C which is equivalent to the dynamic storage elastic modulus at 50 ° C (100%).
It is effectively used to obtain the above rubber member. Less than,
The details of the heat-resistant improver suitably compounded in the rubber member in the present invention will be described. First, the above general formula (I)
In the compound represented by, A represents an alkylene group having 2 to 10 carbon atoms, and the alkylene group may be linear, branched, or cyclic, but is preferably a linear alkylene group. Examples of the linear alkylene group having 2 to 10 carbon atoms include an ethylene group, a trimethylene group, a tetramethylene group, a pentamethylene group, a hexamethylene group, a heptamethylene group, an octamethylene group, and a decamethylene group. Among them, a hexamethylene group is particularly preferable from the viewpoint of the effect. On the other hand, R ¹ and R ² each represent a monovalent organic group containing a nitrogen atom.
A monovalent organic group containing at least one aromatic ring and containing a nitrogen atom, in particular having a carbon atom bonded to a dithio group =
Those containing a bonding group represented by NC (= S)-are preferable. R ¹ and R ² may be the same or different from each other, but are preferably the same from the viewpoint of easy production. As the compound represented by the general formula (I),
For example, the general formula (Ia)

[0018]

Embedded image

Α, ω-bis (N, N′-dihydrocarbylthiocarbamoyldithio) alkane represented by the following formula: In the general formula (Ia), R ^{3 to} R ⁶ each represent an alkyl group, an aryl group, or an aralkyl group, and at least one of R ³ and R ⁴ ;
And at least one of R ⁵ and R ⁶ is an aryl group or an aralkyl group, and n represents an integer of 2 to 10.

Here, the alkyl group has 1 to 1 carbon atoms.
Twenty are preferable, and any of linear, branched and cyclic shapes may be used. Examples of such alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-
Butyl, tert-butyl, various pentyl, various hexyl, various octyl, various decyl, various dodecyl, various tetradecyl, various hexadecyl, various octadecyl, cyclopentyl, cyclohexyl, cyclooctyl, etc. Is mentioned. The aryl group preferably has 6 to 20 carbon atoms, and may have a suitable substituent such as a lower alkyl group on the ring. Examples of such aryl groups include phenyl, tolyl, xylyl, naphthyl, methylnaphthyl and the like. The aralkyl group preferably has 7 to 20 carbon atoms, and may have a suitable substituent such as a lower alkyl group on the ring. Examples of such aralkyl groups include benzyl, methylbenzyl, dimethylbenzyl, phenethyl, methylphenethyl, dimethylphenethyl, naphthylmethyl, (methylnaphthyl) methyl, (dimethylnaphthyl) methyl, Naphthylethyl group, (methylnaphthyl)
Examples include an ethyl group and a (dimethylnaphthyl) ethyl group.

It is preferable that all of R ^{3 to} R ⁶ are the above-mentioned aryl groups or aralkyl groups, and it is particularly preferable that all of them are benzyl groups from the viewpoints of prevention of heat aging and ease of production. is there. Examples of such compounds include 1,2-bis (N, N'-dibenzylthiocarbamoyldithio) ethane; 1,3-bis (N, N'-dibenzylthiocarbamoyldithio) propane; -Bis (N, N'-dibenzylthiocarbamoyldithio) butane; 1,5-bis (N, N'-dibenzylthiocarbamoyldithio) pentane; 1,6-bis (N, N'-dibenzylthiocarbamoyl) 1,7-bis (N, N′-dibenzylthiocarbamoyldithio) heptane; 1,8-bis (N, N′-dibenzylthiocarbamoyldithio) octane; 1,9-bis (N, N'-
Dibenzylthiocarbamoyldithio) nonane; 1,10
-Bis (N, N'-dibenzylthiocarbamoyldithio) decane. Among them, 1,6-bis (N, N′-dibenzylthiocarbamoyldithio) hexane is particularly preferable from the viewpoint of the effect.

The compound represented by the general formula (I) exhibits an effect of improving the heat resistance of the rubber member, but its effect is to increase the heat stability in parallel with the crosslinking at high temperatures. It is thought to be due to the efficient formation of monosulfide bridges. Next, the citraconic imide compound blended as the heat resistance improver is preferably a biscitraconic imide from the viewpoint of the effect. As the biscitraconic imide, for example, a compound represented by the general formula (II)

[0023]

Embedded image

The compounds represented by the following formulas can be preferably mentioned. In the general formula (II), Ar represents an arylene group, and the arylene group is preferably an arylene group having 6 to 20 carbon atoms with or without a substituent on a ring. The substituent is not particularly limited as long as it has no effect on vulcanization and is stable at a high temperature of 170 ° C. or higher. For example, a lower alkyl group or alkoxyl group, a halogen atom, a nitro group, And a cyano group. Examples of the arylene group include a phenylene group and a naphthylene group, and a phenylene group is particularly preferable. On the other hand, Q ¹ and Q ² each represent an alkylene group having 1 to 4 carbon atoms, and the alkylene group may be linear or branched. Examples of such an alkylene group include a methylene group, an ethylene group, a propylene group, and a butylene group. Q ¹ and Q
² may be the same or different, but are preferably the same from the viewpoint of ease of production and the like. Examples of the compound represented by the general formula (II) include 1,2-bis (citraconimidomethyl) benzene; 1,3-bis (citraconimidomethyl) benzene; 1,4-bis (citraconimidomethyl) Benzene; 1,6-bis (citraconimidomethyl) benzene; 2,3-bis (citraconimidomethyl) toluene; 2,4-bis (citraconimidomethyl) toluene; 2,5-bis (citraconimidomethyl) toluene; Examples thereof include 2,6-bis (citraconimidomethyl) toluene and bis (citraconimidoethyl) compounds corresponding thereto. Among these,
From the viewpoint of the effect, 1,6-bis (citraconimidomethyl) benzene is particularly preferred.

This citraconic imide compound has the effect of improving the heat resistance of the rubber member, but its effect is to react with the conjugated C ＝ C in the main chain generated at the time of crosslinking cleavage at a high temperature, and to cause the C—C crosslinking. Is generated at an early stage. Further, the acrylates as the heat resistance improver is preferably a polyvalent ester of a polyhydric alcohol and acrylic acid, or a polyvalent ester of a polyhydric alcohol and acrylic acid and another carboxylic acid, from the viewpoint of the effect. Examples of the polyhydric ester include compounds represented by the general formula (III)

[0026]

Embedded image

The compounds represented by the following formulas can be preferably mentioned. In the general formula (III), A represents a residue of the (p + q) -valent polyhydric alcohol excluding the hydroxyl group, and R represents a hydrogen atom or an acyl group other than an acryloyl group. The acyl group is not particularly limited, but is preferably a saturated or unsaturated aliphatic acyl group having 2 to 20 carbon atoms. p represents an integer of 2 to 10 and q represents an integer of 0 to 8, where p + q = 2 to 10. This general formula (II
Among the compounds represented by I), those wherein p is an integer of 3 to 6, q is an integer of 0 to 3 and p + q = 3 to 6 are preferable from the viewpoint of the effect. General formula (IV) A- (OH) _{p + q} (IV) used for forming the acrylate represented by the general formula (III) (where A and p, q are the same as described above) )), Tri- to hexa-hydric alcohols are preferred, such as glycerin,
Trimethylolethane, trimethylolpropane, diglycerin, pentaerythritol, dipentaerythritol, sorbitol and the like. The general formula (II
As the compound represented by I), from the viewpoint of the effect, a polyvalent ester of dipentaerythritol having 3 to 6 acryloyl groups in one molecule and acrylic acid and 3 to 5 acryloyl groups in one molecule are used. Preferred is an acyl group-modified dipentaerythritol acrylate. Such compounds are commercially available as shown below.
For example, the expression

[0028]

Embedded image A compound represented by a mixture of a compound with a = 5, b = 1 and a compound with a = 6, b = 0) is referred to as “KAYARAD DP
HA ”(trademark, manufactured by Nippon Kayaku Co., Ltd.)

[0029]

Embedded image (R ⁷ represents an Alkynoyl group.) When c = 5 and d = 1, the compound represented by “K
AYARAD D-310 ”[trademark, Nippon Kayaku Co., Ltd.
KAYARAD when c = 3, d = 3
D-330 "[trademark, manufactured by Nippon Kayaku Co., Ltd.]. The above acrylates have an effect of improving the heat resistance of the rubber composition, but the action reacts with the conjugated C = C in the main chain generated at the time of cross-linking cleavage at a high temperature, and effectively causes CC cross-linking. This is considered to be caused by the generation of

The amount of the above-mentioned heat-resistant improver is 10
It is preferably selected in the range of 0.5 to 20 parts by weight with respect to 0 parts by weight. When the amount is less than 0.5 part by weight, the effect of preventing heat aging cannot be sufficiently obtained, and the desired effect of improving heat resistance may not be exhibited. On the other hand, if it exceeds 20 parts by weight, the effect is not so much improved in spite of its amount, which is rather economically disadvantageous and causes other physical properties of the obtained rubber composition to deteriorate. In consideration of the effect of preventing heat aging, other physical properties and economics of the rubber composition, the more preferable compounding amount of the heat resistance improver is 0.7 to 15 parts by weight, particularly preferably 1.0 to 10 parts by weight. Range.

In the present invention, if desired, another heat aging inhibitor can be used in combination with the above-mentioned heat resistance improver. As other heat aging inhibitors, for example, 1,6
-Sodium hexamethylene dithiosulfate dihydrate,
Examples include compounds having two or more ester groups in one molecule. Here, the compound having two or more ester groups in one molecule is not particularly limited, but is preferably acrylate or methacrylate, particularly preferably a polyvalent ester of a polyhydric alcohol and acrylic acid or methacrylic acid. Polyhydric alcohols include ethylene glycol, propylene glycol, butylene glycol, pentanediol,
Alkylene glycols such as hexanediol and the like and multimers thereof, further, methylol-substituted products thereof, pentaerythritols, alkylene oxide adducts of polyhydric alcohols, polyesters or oligoesters having two or more alcoholic hydroxyl groups, etc. Particularly preferred among these are methylol-substituted alkylene glycols and multimers thereof.

Specific examples of the compound having two or more ester groups in one molecule include 1,3-butylene glycol diacrylate; 1,5-pentanediol diacrylate; neopentyl glycol diacrylate;
-Hexanediol diacrylate; diethylene glycol diacrylate; triethylene glycol diacrylate; tetraethylene glycol diacrylate; polyethylene glycol diacrylate; polypropylene glycol diacrylate; pentaerythritol triacrylate; trimethylolpropane triacrylate; pentaerythritol tetraacrylate; Erythritol hexaacrylate; dipentaerythritol pentaacrylate; oligoester polyacrylate; dipropylene glycol dimethacrylate;
Trimethylolethane trimethacrylate; trimethylolpropane trimethacrylate; dipentaerythritol pentamethacrylate; dipentaerythritol trimethacrylate, and the like. Among them, particularly preferred are dipentaerythritol pentamethacrylate; dipentaerythritol trimethacrylate, and trimethylol. It is propane trimethacrylate.

The above-mentioned sodium 1,6-hexamethylenedithiosulfate dihydrate has an effect of suppressing the cross-linkage between polymer molecules constituting the rubber component. On the other hand, the action of the compound having two or more ester groups in one molecule is considered as follows. When the temperature of the rubber composition becomes 170 ° C. or higher, the degradation of the rubber starts, and the cross-linking points and the breaking of the polymer chains start to occur. On the other hand, the C-C cross-linking by the compound proceeds, so that the decrease in the elastic modulus is suppressed. As a result, heat generation is suppressed even at a high temperature. In the rubber composition used in the present invention, in addition to the above components, sulfur, peroxides and other vulcanizing agents, vulcanization accelerators, antioxidants, antioxidants, softeners, inorganic fillers generally used in the rubber industry. Various compounding agents such as materials can be appropriately contained. Further, the rubber composition used in the present invention may be a composite with particles, fibers, cloths and the like of various materials.

Next, the safety tire of the present invention will be described with reference to the drawings. FIG. 1 is a partial cross-sectional view of the left half of an example of the safety tire of the present invention. The safety tire 1 is disposed on a pair of left and right ring-shaped bead cores 4 and radially outside the bead cores 4 in the tire radial direction. Bead filler 5, a carcass layer 2 composed of at least one ply in which a plurality of parallel cords are embedded in a covering rubber, and a belt layer 3 disposed outside the carcass layer 2 in the tire radial direction.
A tread portion 8 disposed radially outside the belt layer 3 in the tire radial direction, and a pair of sidewall portions 6 disposed on the left and right sides of the tread portion 8. At least a portion of the tire side portion extending below the shoulder portion is reinforced with a rubber member layer. This rubber member layer may be arranged on either the inside or outside of the carcass layer 2.

The carcass layer 2 has a folded carcass ply 2a and a down carcass ply 2b. Both ends of the folded carcass ply 2a are folded around the bead core 4 to form folded ends. The bead filler 5 is located between the folded carcass ply 2a and its folded end, and the down carcass ply 2b is arranged between the sidewall portion 6 and the folded end of the folded carcass ply 2a. ing. In FIG. 1 as an example of the present invention, the rubber member layer 7 having specific physical properties according to the present invention is disposed on the inner peripheral surface of the sidewall portion of the folded carcass ply 2a. The rubber member may be a composite with organic fibers or inorganic particles, but as described above, the minimum value of the dynamic storage modulus at 200 to 250 ° C is the dynamic storage modulus at 50 ° C. Must be 75% or more. The rubber member preferably has a dynamic storage modulus at 50 ° C. of 2 to 20 MPa, more preferably 3 to 16 MPa, and particularly preferably 3 to 20 MPa.
It is preferably in the range of 10 MPa. The sectional shape is not particularly limited as long as it has a function of reinforcing the side. This rubber member layer is preferably arranged in a region of 50% or more, preferably 60 to 80% of the tire section height in the tire radial direction around the tire maximum width position.

As described above, the dynamic storage modulus at 50 ° C. is 2 to 20 MPa, and the minimum value of the dynamic storage modulus at 200 to 250 ° C. is less than the dynamic storage modulus at 50 ° C. In the pneumatic tire of the present invention in which a rubber member having physical properties of 75% or more, particularly equivalent (100%) or more, is disposed on the tire side portion, the deterioration of ride comfort due to the increase in the elastic modulus during normal running is substantially. Does not happen. Also, due to large deformation due to puncture of the tire, etc., even if the temperature of the rubber composition becomes 170 ° C. or more, a decrease in the elastic modulus is suppressed. It is possible to achieve both the vibration riding comfort performance and the run-flat durability performance at the time of normal driving use under internal pressure.

[0037]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Various measurements were obtained according to the following methods. (1) Microstructure (Amount of Vinyl Bond) The amount of vinyl bond (1,2-bond) in the conjugated diene unit was determined by an infrared method (Morello method). (2) Characteristics such as dynamic storage elastic modulus (E ') From a 2 mm thick slab sheet obtained by vulcanizing a rubber composition at 160 ° C. for 12 minutes, a width of 5 mm and a length of 4
A sheet of 0 mm was cut out and used as a sample. Using a spectrometer manufactured by Ueshima Seisakusho Co., Ltd., the distance between the chucks was 10 mm, the initial strain was 200 micrometers (microns), the dynamic strain was 1%, the frequency was 52 Hz, the measurement start temperature was 25 ° C., and the heating rate was 3 ° C. / Min, measurement end temperature 250
The dynamic storage modulus was measured under the measurement conditions of ° C. Also, 5
The ratio of the minimum value of the dynamic storage modulus in the range of 200 to 250 ° C. to the dynamic storage modulus of 0 ° C. was indicated by an index. The larger the index is, the smaller the decrease of the dynamic storage modulus due to the high temperature is.

(3) Riding Comfort Each prototype tire is mounted on a passenger car, and a riding comfort feeling test is performed by two specialized drivers.
And the average was calculated. The larger the value, the better the ride comfort. (4) Run flat durability Each prototype tire was assembled on a rim at normal pressure, sealed at an internal pressure of 200 kPa, left at room temperature of 38 ° C. for 24 hours, the core of the valve was removed, and the internal pressure was set to atmospheric pressure. 58N (4
A drum running test was performed under the conditions of 67 kgf), a speed of 89 km / h, and a room temperature of 38 ° C. The running distance up to the occurrence of the failure at this time is defined as run flat durability. Comparative Examples 1 to 100 are used for Examples 1 to 3, Comparative Example 2 is set to 100 for Example 4, and Comparative Examples 2 to 100 are used for Examples 5 to 7. Example 3 is 1
The index was set to 00. Further, in Examples 8 to 11, Comparative Example 4 was set to 100, Example 12 to Comparative Example 5 was set to 100, and Examples 13 to 15 were set to Comparative Example 6 as 100. The larger the index, the better the run flat durability. (5) Rolling Resistance The rolling resistance was measured by the coasting method. The tire internal pressure was 1.7 kg / cm ² , the load was JIS 100% load, and the coasting start speed was 100 km / hr. For Example 3, Comparative Example 1 was set to 100 and Example 4
Is represented by an index with Comparative Example 2 being 100, and Examples 5 to 7 with Comparative Example 3 being 100. In Examples 8 to 11, Comparative Example 4 was set to 100, Example 12 was set to Comparative Example 5, and Examples 13 to 15 were set to Comparative Example 6.
The index was set to 00. The lower the index, the lower the rolling resistance.

Production Example 1 3 kg of cyclohexane, 500 g of butadiene monomer and 0.225 mmol of ditetrahydrofurylpropane (DTHFP) were injected into an 8 liter pressure-resistant reactor equipped with a dried, nitrogen-substituted temperature-adjusting jacket. .5
After adding mmol of n-butyllithium (BuLi), polymerization was carried out at a starting temperature of 40 ° C. for 1 hour. The polymerization is
The jacket temperature was adjusted so that the final temperature did not exceed 75 ° C. under the condition of elevated temperature. The polymerization system was uniformly transparent without any precipitation from the start to the end of the polymerization. The polymerization conversion was almost 100%. After 0.11 ml of SnCl ₄ (1M cyclohexane solution) was added to this polymerization system as a terminal modifier, a modification reaction was carried out for 30 minutes. Thereafter, a 5% solution of 2,6-di-t-butyl-p-cresol (BHT) in isopropanol (0.5%) was added to the polymerization system.
The reaction was stopped by adding milliliters, and the polymer was dried according to a conventional method to obtain a tin-modified butadiene rubber. As a result of analysis of the obtained rubber, the vinyl bond amount was 25%, the molecular weight (Mw) was 200,000, and the molecular weight distribution (Mw / Mn) was 1.
There was one.

Examples 1 to 15 and Comparative Examples 1 to 6 Rubber compositions having the composition shown in Table 1 were prepared.
This rubber composition was used as a rubber member for the tire side portion, and Examples 1 to 4, Examples 8 to 15, Comparative Examples 1 and 2, and Comparative Example 4
1 to 6 are arranged on the inner side of the tire side portion (FIG. 1).
For Examples 5 to 7 and Comparative Example 3, the side portions were arranged outside the carcass layer (not shown), and radial tires for passenger cars of size 205 / 60R15 were manufactured according to a conventional method. In addition, the maximum thickness of the rubber member layer is described in Table 1 as a gauge of the rubber member. The obtained tires were evaluated for ride comfort, run flat durability, and rolling resistance. The results are shown in Table 1.

[0041]

[Table 1]

[0042]

[Table 2]

(Note) * 1) Butadiene rubber: "BR01" (cis-1,4-polybutadiene, manufactured by JSR Co., 2.5% vinyl bond) * 2) Buna VI 47-0 (trademark) Bayer, butadiene rubber, vinyl bond content 47%) * 3) Buna VI 70-0 HM (trademark, Bay)
er Co., Ltd., butadiene rubber, vinyl bond content 70%) * 4) Buna VI 80-0 HM (trademark, Bay)
* 5) Tin-modified butadiene rubber (prototype according to Production Example 1) * 6) Carbon black: FEF [Asahi Carbon Co., Ltd.
* 7) Softener: spindle * 8) Nocrack 6C [trademark, Ouchi Shinko Chemical Industry Co., Ltd.] * 9) Noxeller NS [trademark, Ouchi Shinko Chemical Industry Co., Ltd.] * 10) Compound A of general formula (I): 1,6-bis (N,
N'-dibenzylthiocarbamoyldithio) hexane (VULCUEN TRIAL PRODUCTUCKA)
9188 BAYER) * 11) Compound B of the general formula (I): 1,6-bis (N,
N'-dimethylthiocarbamoyldithio) hexane (prototype synthetic product) * 12) Compound C of general formula (I): 1,6-bis (N,
N'-Diethylthiocarbamoyldithio) hexane (prototype synthetic product) * 13) Compound D of general formula (I): 1,6-bis (N,
N'-di (2-ethylhexyl) thiocarbamoyldithio) hexane (prototype synthetic product) * 14) Compound E of general formula (I): 1,6-bis (benzothiazolyldithio) hexane (prototype synthetic product) * 15) Citraconimide compound A: PERKALIN
K 900 (trademark, manufactured by FLEXSYS) * 16) Citraconimide compound B: N, N'-m-phenylene-biscitraconimide prototype synthetic product * 17) Acrylates A: KAYARAD D-31
0 [trademark, manufactured by Nippon Kayaku Co., Ltd.] * 18) Acrylates B: KAYARAD DPHA
[Trademark, manufactured by Nippon Kayaku Co., Ltd.] * 19) Acrylates C: KAYARAD D-33
0 [trademark, manufactured by Nippon Kayaku Co., Ltd.]

From the above results, it can be seen that the safety tire of the present invention in which the rubber member having the specific physical properties is disposed at the tire side portion has excellent ride comfort and rolling resistance by greatly reducing the side member gauge. It can be seen that the run-flat durability was excellent because the reduction was achieved and the decrease in the elastic modulus at a high temperature was suppressed at the same time.

[0045]

According to the present invention, by arranging the rubber member having the above-mentioned specific physical properties on the tire side portion, it is possible to sacrifice the ride comfort during normal running.
The run flat durability and rolling resistance of the tire can be significantly improved.

[Brief description of the drawings]

FIG. 1 is a partial sectional view of an example of the safety tire of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Safety tire of this invention 2 Carcass layer 2a Folded carcass ply 2b Down carcass ply 3 Belt layer 4 Bead core 5 Bead filler 6 Side wall part 7 Side rubber member layer 8 Tread part

Claims (11)

[Claims] 1. A carcass layer comprising: a carcass layer; a tread portion disposed radially outward of the carcass layer; and a pair of side portions disposed on left and right sides of the tread portion. A safety tire comprising a rubber member having a minimum dynamic storage elastic modulus at 200 to 250 ° C. of 75% or more of the dynamic storage elastic modulus at 50 ° C. 2. A rubber having a minimum dynamic storage modulus at 200 to 250 ° C. of 75% or more of a dynamic storage modulus at 50 ° C. on the inner surface of the tire adjacent to the carcass layer at the side portion. The safety tire according to claim 1, wherein a member is disposed. 3. A rubber member having a minimum dynamic storage elastic modulus at 200 to 250 ° C. of 85% or more of a dynamic storage elastic modulus at 50 ° C. 2
Safety tire according to. 4. A rubber member having a minimum dynamic storage modulus at 200 to 250 ° C. equal to or greater than a dynamic storage modulus at 50 ° C. Safety tire according to. 5. A rubber member having a minimum dynamic storage modulus at 200 to 250 ° C. which is at least 10% higher than a dynamic storage modulus at 50 ° C.
Safety tire according to. 6. A rubber member having a minimum dynamic storage modulus at 200 to 250 ° C. higher than the dynamic storage modulus at 50 ° C. by 20% or more.
Safety tire according to. 7. A dynamic storage modulus at 50 ° C. of 2 to 20.
The safety tire according to any one of claims 1 to 6, wherein a rubber member having a range of MPa is disposed. 8. A dynamic storage modulus at 50 ° C. of 3-16.
The safety tire according to any one of claims 1 to 6, wherein a rubber member having a range of MPa is disposed. 9. A dynamic storage modulus at 50 ° C. of 3 to 10
The safety tire according to any one of claims 1 to 6, wherein a rubber member having a range of MPa is disposed. 10. A carcass layer comprising: a carcass layer; a tread portion disposed radially outward of the carcass layer; and a pair of side portions disposed on the left and right sides of the tread portion.
The side portion has a dynamic storage modulus at 50 ° C. of 2 to 20.
By placing a rubber member having a dynamic storage modulus at 200 to 250 ° C. and a minimum value of 75% or more of the dynamic storage modulus at 50 ° C. at the time of the internal pressure of the pneumatic tire, A method to achieve both vibration riding comfort performance and run-flat durability performance during normal use. 11. A carcass layer comprising: a carcass layer; a tread portion disposed radially outward of the carcass layer; and a pair of side portions disposed on the left and right sides of the tread portion.
The side portion has a dynamic storage modulus at 50 ° C. of 2 to 20.
The minimum value of the dynamic storage modulus at 200 to 250 ° C. is the same as or higher than the dynamic storage modulus at 50 ° C., so that the rubber member having the same or higher than the dynamic storage modulus at 50 ° C. A method that achieves both vibration riding comfort performance and run-flat durability performance during driving use.