JP2002037927A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a pneumatic tire excellent in both of rolling resistance and run flat durability while maintaining good performances of comfortableness to ride during normal running. SOLUTION: This pneumatic tire is characterized in that a rubber composition constituting at least one of reinforcing rubbers in a bead filler and a sidewall part is obtained by compounding (A) a rubber component containing a conjugated diene-based polymer having >=25% vinyl bond content in a conjugated diene unit and 200,000-900,000 weight-average molecular weight (Mw) and 1-4 molecular weight distribution (Mw/Mn) which is a ratio of the weight-average molecular weight to the number-average molecular weight (Mn) with (B) at least one kind of compound selected from a compound represented by the general formula (I) R1-S-S-A-S-S-R2 (I) (wherein, A denotes a 2-10C alkylene group; and R1 and R2 denote each independently a monovalent organic group containing nitrogen atom), a citraconimide compound and a compound of acrylates.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire, and more particularly, to a rubber composition comprising a rubber composition containing a specific conjugated diene polymer and a bead filler and a side wall. The present invention relates to a pneumatic tire used for at least one of the following (hereinafter sometimes referred to as a side reinforcing layer), and more particularly to a pneumatic tire having improved run flat durability.

[0002]

2. Description of the Related Art Conventionally, in a tire, a side reinforcing layer made of a rubber composition alone or a composite of a rubber composition and fibers is provided in order to improve the rigidity of a sidewall portion. However, in the rubber compositions used for these tires, in particular, the tire travels in a state where the internal pressure of the tire (hereinafter, referred to as the internal pressure) is reduced due to puncture of the tire, so-called run-flat travel, When the temperature is 200 ° C. or higher, a crosslinked portion formed by vulcanization or the like, or a polymer constituting the rubber component, tends to be cut. For this reason, when the elastic modulus of the rubber composition decreases, the deflection of the tire increases, heat is generated, and the breaking limit of the side reinforcing layer is reduced. As a result, the tire may fail relatively early. was there.

As one of means for delaying the process leading to such a failure as much as possible, the elastic modulus of the rubber composition to be used is made as large as possible by changing the compounding, or the loss tangent (tan δ) thereof is set as small as possible. Therefore, a method of suppressing heat generation of the rubber composition itself is known, but there is a limit in the conventional approach from the viewpoint of compounding,
In run-flat driving, the only way to ensure a certain durable distance is to increase the amount of side reinforcement layers and bead filler. As a result, during normal driving, riding comfort, noise level, weight, etc. The fact is that this is causing undesirable situations.

[0004]

Under such circumstances, the present invention maintains good ride comfort during normal running by devising a rubber component used for a bead filler and a sidewall reinforcing layer in such a situation. It is another object of the present invention to provide a pneumatic tire excellent in both rolling resistance and run flat durability.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, a rubber composition containing a specific conjugated diene-based polymer and a specific compound has been added to a bead filler and It has been found that the pneumatic tire used for at least one of the side reinforcing layers has remarkably improved durability especially in run-flat running. The present invention has been completed based on such findings. That is, the present invention comprises a pair of left and right bead cores, and a bead filler disposed radially outward of the bead core, a rubber composition constituting the bead filler,
(A) The conjugated diene unit has a vinyl bond amount of 25
% Or more, a conjugated diene having a weight average molecular weight (Mw) of 200,000 to 900,000 and a molecular weight distribution (Mw / Mn) represented by a ratio of the weight average molecular weight to the number average molecular weight (Mn) of 1 to 4. A rubber component containing a base polymer; and (B) a general formula (I) R ¹ -SSSASR ² (I) wherein A is an alkylene having 2 to 10 carbon atoms. Groups, R ¹ and R
² independently represents a monovalent organic group containing a nitrogen atom. ), And at least one compound selected from citraconic imide compounds and acrylate compounds.

Further, the present invention provides a carcass layer, a tread portion disposed radially outside the carcass layer in the tire radial direction,
It comprises a pair of sidewall portions disposed on the left and right sides of the tread portion, and a rubber reinforcing layer disposed on the sidewall portion, and constitutes a rubber reinforcing layer disposed on the sidewall portion. The rubber composition has (A) a conjugated diene unit having a vinyl bond content of 25% or more, a weight average molecular weight (Mw) of 200,000 to 900,000, and a ratio represented by the ratio of the weight average molecular weight to the number average molecular weight (Mn). A rubber component containing a conjugated diene-based polymer having a molecular weight distribution (Mw / Mn) of 1 to 4; and (B) a compound represented by the general formula (I): R ¹ -S-S-A-S-S-S-R ^2. ·· (I) (wherein A is an alkylene group having 2 to 10 carbon atoms, R ¹ and R
² independently represents a monovalent organic group containing a nitrogen atom. ), And at least one compound selected from citraconic imide compounds and acrylate compounds.

The present invention further provides a pair of left and right bead cores, a bead filler and a carcass layer disposed radially outward of the bead core in a tire radial direction, and a tread portion disposed radially outward of the carcass layer in the tire radial direction. It comprises a pair of sidewall portions disposed on the left and right sides of the tread portion, and a rubber reinforcing layer disposed on the sidewall portions, and is disposed on the rubber composition and the sidewall portion constituting the bead filler. Both of the rubber compositions constituting the provided rubber reinforcing layer have (A) a conjugated diene unit having a vinyl bond amount of 25% or more, a weight average molecular weight (Mw) of 200,000 to 900,000, and a weight average molecular weight of The molecular weight distribution (Mw / Mn) represented by the ratio of the number average molecular weight (Mn) is 1
A rubber component containing a conjugated diene-based polymer,
(B) Formula (I) R ¹ -SSSASR ² ... (I) wherein A is an alkylene group having 2 to 10 carbon atoms, R ¹ and R
² independently represents a monovalent organic group containing a nitrogen atom. ), And at least one compound selected from citraconic imide compounds and acrylate compounds.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a component containing a conjugated diene polymer having a vinyl bond content, a weight average molecular weight (Mw) and a molecular weight distribution (Mw / Mn) in a conjugated diene unit limited to the above-mentioned specific range. A) and a rubber composition obtained by blending at least one compound (B) selected from the compound of the general formula (I), the citraconimide compound and the acrylate compound in at least one of the bead filler and the side reinforcing layer. In the tire used, the effect of suppressing the decrease in the elastic modulus due to the temperature rise of the rubber composition is remarkable, so that the increase in the deflection of the tire due to run flat running can be suppressed and the run flat durability can be improved.

First, the component (A) will be described in more detail. In the present invention, the vinyl bond amount in the conjugated diene unit needs to be 25% or more of the diene bond portion of the polymer. 2 vinyl bonds
If it is less than 5%, the decrease in the elastic modulus due to the sulfur crosslinking cut at a high temperature of 150 ° C. or more becomes dominant, and the effect of suppressing the decrease in the elastic modulus due to the temperature rise cannot be sufficiently expected. From this point, the vinyl bond amount is preferably 30% or more, and more preferably 3% or more.
5% or more is preferable. In particular, it is preferably 40 to 60%. Further, the weight average molecular weight (Mw) of the polymer needs to be 200,000 to 900,000. If it is less than 200,000, the rubber composition has poor tensile properties and rolling resistance,
If it exceeds 10,000, workability tends to be poor. From this point, M
w is preferably 300,000 to 800,000, particularly preferably 300,000 to 700,000.

Further, the molecular weight distribution of the polymer (Mw /
Mn) needs to be 1 to 4. Mw
If / Mn exceeds 4, the heat build-up tends to decrease, and it is 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.
The conjugated diene-based polymer in the present invention is preferably a conjugated diene homopolymer and / or a conjugated diene-aromatic vinyl copolymer, and also includes these modified polymers as described later. Here, examples of the conjugated diene monomer include 1,3-butadiene, 1,3-pentadiene, and 1,3-hexadiene.
3-Butadiene is preferred. Examples of the aromatic vinyl monomer used for copolymerization with the conjugated diene monomer include styrene, α-methylstyrene, 1-vinylnaphthalene, 3-vinyltoluene, ethylvinylbenzene, divinylbenzene, and 4-vinylbenzene. Cyclohexylstyrene, 2,
Examples include 2,6-tolylstyrene, and among them, styrene is preferred.

The conjugated diene-based polymer can be produced by various methods, and the polymerization system may be either a batch polymerization system or a continuous polymerization system. 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 in combination 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. Can be suitably changed by adding an appropriate amount of the ether and / or tertiary amine compound to the polymerization system.

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 improve low heat build-up in a carbon black compounded rubber composition. In particular, those having a branched structure obtained by using a polyfunctional modifier are preferred. The above modified polymer is produced by a known method, and is usually obtained by initiating polymerization with an organolithium initiator and adding various modifiers to a solution of a polymer having a lithium active terminal (Japanese Patent Publication No. Hei 6-1994). 891
No. 83, JP-A-11-29659, etc.). For example, a tin atom is introduced by a tin compound such as tin tetrachloride, tributyltin, dioctyltin dichloride, dibutyltin dichloride, and triphenyltin chloride, and a nitrogen atom is an isocyanate compound such as diisocyanatodiphenylmethane and 4- (dimethylamino). ) It is introduced by a nitrogen-containing compound such as aminobenzophenone compound such as benzophenone, 4-dimethylaminobenzylideneaniline, dimethylimidazolidinone, 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, 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.

In the pneumatic tire of the present invention, the rubber component used in the bead filler or the rubber reinforcing layer in the side wall portion has a vinyl bond content of 25% or more in the conjugated diene unit and a weight average molecular weight (Mw) of 200,000 to 200,000. 9
And the weight average molecular weight and the number average molecular weight (M
n) a molecular weight distribution (Mw / Mn) represented by a ratio of 1 to 4
And a conjugated diene-based polymer containing a tin atom and / or a nitrogen atom in the molecule, particularly preferably at least 50% by weight of the total amount of the rubber component, and more preferably 100%. If the amount is less than 50% by weight, a decrease in rubber elasticity due to a rise in temperature may not be suppressed. In this respect, the conjugated diene-based polymer is more preferably contained in an amount of 60% by weight or more, and more preferably 80% by weight or more. In the rubber composition 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 (IR); cis-1, 4-polybutadiene rubber (B
R), styrene-butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR) and the like. These rubbers may be used in combination of two or more.

Hereinafter, the component (B) will be described in more detail. In the rubber composition used in the present invention, in order to improve heat resistance, as the component (B), at least one compound selected from a compound represented by the general formula (I), a citraconic imide compound and an acrylate compound Is required. Hereinafter, the details of each of these compounds will be described. The compound in the component (B) is a compound represented by the general formula (I) R ¹ -SSA-S-S-R ² ... (I).

In the general formula (I), A represents 2 carbon atoms.
And 10 to 10 alkylene groups, which may be linear, branched or cyclic, but are preferably linear alkylene groups. 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, each of R ¹ and R ² represents a monovalent organic group containing a nitrogen atom, and is preferably a monovalent organic group containing at least one aromatic ring and containing a nitrogen atom. Those containing a bonding group represented by = NC (= S)-bonded to a dithio group 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, a compound represented by the general formula (Ia)

[0017]

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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 are aryl. And n is 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 viewpoint 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 these, 1,6-bis (N, N′-dibenzylthiocarbamoyldithio) hexane is particularly preferable from the viewpoint of the effect.

The compound represented by the general formula (I) has an effect of improving the heat resistance of the rubber composition, 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. As the citraconic imide compound as the component (B) used in the rubber composition used in the present invention, biscitraconic imides are preferable from the viewpoint of the effect. (II)

[0022]

Embedded image

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 having or not having a substituent on a ring. The substituent is not particularly limited as long as it has no influence 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.

The citraconic imide compound of the component (B) exhibits an effect of improving the heat resistance of the rubber composition, but its effect is to react with a conjugated CＣC in the main chain generated at the time of crosslinking cleavage at a high temperature. However, it is considered that this is due to the early generation of CC crosslinks. Further, as the acrylate as the component (B), a polyhydric ester of a polyhydric alcohol and acrylic acid, or a polyhydric ester of a polyhydric alcohol and acrylic acid and another carboxylic acid is preferable from the viewpoint of the effect, As the polyhydric ester, for example, a compound represented by the general formula (III)

[0025]

Embedded image

Compounds represented by the following formulas can be preferably mentioned. In the general formula (III), A represents a residue excluding a hydroxyl group of a (p + q) -valent polyhydric alcohol, 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 in which p is an integer of 3 to 6 and q is an integer of 0 to 3 and p + q = 3 to 6 are preferable in terms of 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 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

[0027]

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

[0028]

Embedded image (R ⁷ represents an alkynyl 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 acrylates of the component (B) include:
It has the effect of improving the heat resistance of the rubber composition, but its action is due to the conjugated C
= C, which is believed to be due to the effective formation of CC bridges.

The compounding amount of the component (B) is as described in the above (A).
0.5 parts by weight based on 100 parts by weight of the rubber component
It is selected in the range of ２０20 parts by weight. If the amount is less than 0.5 parts by weight, the effect of preventing heat aging cannot be sufficiently obtained, and the desired effect of improving heat resistance may not be exhibited. Meanwhile, 2
If the amount exceeds 0 parts by weight, the effect is not so much improved in spite of the 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 component (B) is 0.7
To 15 parts by weight, particularly preferably 1.0 to 10 parts by weight.

In the present invention, if desired, another heat aging inhibitor can be appropriately used in combination with the compound of the above-mentioned component (B). Other heat aging inhibitors include:
For example, sodium 1,6-hexamethylenedithiosulfate
Examples include dihydrate and 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,
Preference is given to acrylates or methacrylates, in particular polyhydric esters of polyhydric alcohols with acrylic acid or methacrylic acid. Examples of the polyhydric alcohol include alkylene glycols such as ethylene glycol, propylene glycol, butylene glycol, pentanediol, and hexanediol and multimers thereof, and further, methylol-substituted products thereof, pentaerythritols, and alkylene oxide adducts of polyhydric alcohols. And polyesters or oligoesters having two or more alcoholic hydroxyl groups. Of these, particularly preferred 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, with dipentaerythritol pentamethacrylate; dipentaerythritol trimethacrylate; Propane trimethacrylate.

The above-mentioned sodium 1,6-hexamethylenedithiosulfate dihydrate has an action 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. 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-mentioned 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.

The rubber composition of the present invention is excellent in heat resistance and durability, and particularly as a bead filler rubber for tires.
It is also suitable as a sidewall reinforcing rubber for tires. The pneumatic tire of the present invention can be manufactured by a conventional method by applying the rubber composition to at least one of a bead filler and a rubber reinforcing layer provided on a sidewall portion.

Next, regarding the pneumatic tire of the present invention,
This will be described with reference to the accompanying drawings. FIG. 1 is a partial sectional view of the left half of an example of the pneumatic tire of the present invention. The pneumatic tire 1 includes a pair of left and right ring-shaped bead cores 4 and a radially outer portion of the bead cores 4. A 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 a tire radial direction. A tread portion 8 disposed outside the belt layer 3 in the tire radial direction; a pair of sidewall portions 6 disposed on the left and right sides of the tread portion 8; and a rubber disposed on the sidewall portion 6. A reinforcing layer 7 is provided.

The carcass layer 2 is a folded carcass ply 2
a and the down carcass ply 2b, and both end portions of the folded carcass ply 2a are folded around the bead core 4 to form a folded end portion. The bead filler 5 is located between the folded carcass ply 2a and its folded end.
b is the side wall portion 6 and the folded carcass ply 2
It is arranged between the folded end of FIG. The rubber reinforcing layer 7 is disposed on the inner peripheral surface of the sidewall portion of the folded carcass ply 2a. The rubber of the rubber reinforcing layer 7 that reinforces the sidewall portion 6 may be a composite with organic fibers, inorganic particles, or the like, and its cross-sectional shape is not particularly limited as long as it has a side reinforcing function. .

In the pneumatic tire of the present invention, at least one of the bead filler 5 and the rubber reinforcing layer 7 is formed using the rubber composition containing the conjugated diene polymer. In the pneumatic tire of the present invention, the ride comfort and the noise level do not substantially deteriorate due to the increase in the elastic modulus during normal running. Further, even if the temperature of the rubber composition becomes 170 ° C. or more due to a large deformation due to a puncture of the tire or the like, a decrease in the elastic modulus is suppressed, so that heat generation at a high temperature is suppressed. Therefore, the pneumatic tire of the present invention using this rubber composition for the bead core or the rubber reinforcing layer of the side wall portion has a significantly improved durability, particularly in run-flat running, and can significantly extend the running distance. .

[0037]

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 of Polymer 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 elastic modulus in the region of 200 to 250 ° C. to the dynamic storage elastic 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 was mounted on a passenger car, and a riding comfort feeling test was conducted by two specialized drivers, and 1-10
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 to load 4. 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 run distance until the occurrence of a failure at this time is defined as run flat durability, and the index is set to 100 for Comparative Examples 1 for Examples 1 to 4, and 100 for Comparative Examples 2 for Examples 5 to 33 and Comparative Example 3. Expressed.
In addition, Examples 34 and 35 are represented by an index with Comparative Example 4 being 100, and Examples 36 and 37 are represented by an index with Comparative Example 5 being 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 4, Comparative Example 1 was set to 100 and Example 5
Comparative Examples 3 to 33 and Comparative Example 3 were represented by indices with Comparative Example 2 being 100. In addition, Examples 34 and 35 are represented by an index with Comparative Example 4 being 100, and Examples 36 and 37 are represented by an index with Comparative Example 5 being 100. The lower the index, the lower the rolling resistance.

Production Examples 1 to 6 (Polymers C to H) A continuously dried 15 mol% solution of butadiene in cyclohexane was placed in an 8 liter pressure-resistant reactor equipped with a dried, nitrogen-purged, temperature-adjusting jacket per minute. It was introduced at a rate of 200 g. From the same port, ditetrahydrofurylpropane (DTHFP) as a cyclohexane solution (1 mol / L) was added at 0.03 mmol / min.
And n-butyllithium (BuLi) as an n-hexane solution (4.5 mmol / liter) in 0.3 mmo
It was introduced continuously at a rate of 1 / min. The polymerization system was always kept at 80 ° C., and the produced polymer was continuously taken out from the upper part of the reactor and poured into a 1% solution of BHT in isopropanol to obtain a polymer. The polymerization system was uniformly transparent from the start to the end of the polymerization without any precipitation. The polymerization conversion was almost 100%. The obtained polymer solid was dried to obtain a rubbery polymer C. In addition, polymers D to H were obtained in the same manner as described above, except that the introduction rates (mmol / min) of BuLi and DTHFP were changed to those shown in Table 1 in the method for producing polymer C. With respect to the obtained polybutadiene polymers C to H, the microstructure (vinyl bond amount), molecular weight (Mw) and molecular weight distribution (Mw /
Mn) was measured. Table 1 shows the results.

[0040]

[Table 1]

(Note) Mw: weight average molecular weight (× 10 ⁴ ) Mw / Mn: molecular weight distribution Production Examples 7 to 23 (Polymers A, B, I to W) Dried and nitrogen-substituted with temperature-adjusted jacket 8 3 kg of cyclohexane, 500 g of butadiene monomer, and 0.225 mmol of ditetrahydrofurylpropane (DTHFP) were injected into a liter pressure-resistant reactor, and then 4.5 g.
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 elevated temperature conditions. The polymerization system was uniformly transparent from the start to the end of the polymerization without any precipitation. The polymerization conversion was almost 100%. To this polymerization system, 0.11 ml of SnCl ₄ (TTC, 1 M cyclohexane solution) was added as a terminal modifier, followed by a modification reaction for 30 minutes. Thereafter, 2,6-di-t-butyl- was added to the polymerization system.
0.5 ml of a 5% solution of p-cresol (BHT) in isopropanol was added to stop the reaction, and the polymer was dried in a conventional manner to obtain a polymer A. In addition, polymers B, I to V were obtained in the same manner as described above, except that the amounts of BuLi and DTHFP and the types and amounts of the terminal modifiers were changed according to Table 1 in the method for producing polymer A. Further, the polymer W was prepared in the same manner as in Production Example I except that TTC was not used as a terminal modifying agent in the production method of Production Example I.
Got. Microstructure (vinyl bond amount), molecular weight (Mw) and molecular weight distribution (Mw / Mn) of the obtained polymers A, B, and I to W were measured. Table 1 shows the results.

Production Examples 24 and 25 (Polymers X and Y) A dried and nitrogen-substituted 8-liter pressure-resistant reactor equipped with a temperature control jacket was charged with 3 kg of cyclohexane, 500 g of butadiene monomer and 1.6 mmol of ditetrahydrofuryl. Inject propane (DTHFP) and add 4 mmol
Of n-butyl lithium (BuLi) was added thereto, and 0.8 mmol of hexamethyleneimine (HMI) was quickly added thereto, and polymerization was carried out at a starting temperature of 40 ° C. for 1 hour.
The polymerization was performed under elevated temperature conditions, and the jacket temperature was adjusted so that the final temperature did not exceed 75 ° C. The polymerization system was uniformly transparent from the start to the end of the polymerization without any precipitation. The polymerization conversion was almost 100%. 0.81 ml of SnCl ₄ (TTC, 1 M cyclohexane solution) was added to this polymerization system as a terminal modifier,
The denaturation reaction was performed for minutes. Thereafter, 0.5 mL of a 5% solution of BHT in isopropanol was added to the polymerization system to stop the reaction, and the polymer was dried by a conventional method to obtain a polymer X. In the method for producing the polymer X, except that the amount of BuLi and the type of the terminal modifier were changed to those shown in Table 2,
A polymer Y was obtained in the same manner as in the production method of the polymer X. With respect to the modified polybutadiene polymers X and Y obtained, the microstructure (vinyl bond amount), molecular weight (Mw) and molecular weight distribution (M
w / Mn) was measured. Table 2 shows the results.

[0043]

[Table 2]

(Note) 1) Molecular weight Mw: weight average molecular weight (× 10 ⁴ ) Mw / Mn: molecular weight distribution 2) Terminal modifier TTC: tin tetrachloride TBTC: tributyltin (Bu ₃ SnCl) DOTDC: dioctyltin dichloride (Oct) ₂ Sn
Cl ₂ ) DBTDC: dibutyltin dichloride (Bu ₂ SnCl
₂ ) DMABP: 4- (dimethylamino) benzophenone DMABA: 4-dimethylaminobenzylideneaniline DMABB: 4-dimethylaminobenzylidenebutylamine

Embedded image DMI: dimethylimidazolidinone

Embedded image NMP: N-methylpyrrolidone

Embedded image c-MDI: Crude MDI / Made by Nippon Polyurethane, M
R400

Embedded image 3) Modification initiator LHMI: reaction product of n-butyllithium (n-BuLi) and hexamethyleneimine (HMI)

Production Examples 26 to 29 (Polymers BA to BD) In an 8 liter pressure-resistant reactor equipped with a dried and nitrogen-substituted temperature-adjusting jacket, 3 kg of cyclohexane, 475 g of butadiene monomer, 25 g of styrene, 2.5 mm
1 of ditetrahydrofurylpropane (DTHFP) was injected. After adding 5.5 mmol of n-butyllithium (BuLi) thereto, polymerization was carried out at a starting temperature of 40 ° C. for 1 hour. The polymerization is carried out under elevated temperature and the final temperature is 75
The jacket temperature was adjusted so as not to exceed ℃. The polymerization system was uniformly transparent from the start to the end of the polymerization without any precipitation. The polymerization conversion was almost 100%.
After 5 ml of c-MDI (1M cyclohexane solution) was further added to the polymerization system, a denaturation reaction was performed for 30 minutes. Thereafter, 0.5 ml of a 5% solution of BHT in isopropanol was added to the polymerization system to stop the reaction, and the polymer was dried according to a conventional method to obtain a polymer BA. Further, a polymer BB was obtained in the same manner as described above, except that the amounts of butadiene and styrene were changed to those shown in Table 3 in the method for producing the polymer BA. Further, in the above process for producing the polymer BA, the polymers BC and BD were produced in the same manner as described above, except that the amounts of butadiene, styrene and DTHP were changed and c-MDI was not added as a terminal modifier.
Got. The microstructure (vinyl bond amount), molecular weight (Mw) and molecular weight distribution (Mw / Mn) of the terminal-modified or unmodified styrene-butadiene polymers BA to BD thus obtained were measured. Table 3 shows the results.

Production Examples 30, 31 (Polymer BE, BF) A dried, nitrogen-substituted, 8 liter pressure-resistant reactor equipped with a temperature-adjusted jacket was charged with 3 kg of cyclohexane, 475 g of butadiene monomer, 25 g of styrene, 0.2 mmo.
l of ditetrahydrofurylpropane (DTHFP) and 0.2 mmol of a potassium tertiary millate in cyclohexane solution were injected. This has 4.5 mmol of n
After the addition of -butyllithium (BuLi), polymerization was carried out for 1 hour at a starting temperature of 40 ° C. The polymerization was performed under elevated temperature conditions, and the jacket temperature was adjusted so that the final temperature did not exceed 75 ° C. The polymerization system was uniformly transparent from the start to the end of the polymerization without any precipitation. The polymerization conversion is approximately 1
00%. Isopropanol was added to the polymerization system to stop the reaction, and the polymer solid was dried according to a conventional method to obtain a polymer BE. Further, in the above process for producing the polymer BE, except that the amounts of butadiene and styrene were changed to those shown in Table 3, the polymer BF was produced in the same manner as described above.
Got. About the obtained polymers BE and BF, microstructure (vinyl bond amount), molecular weight (Mw) and molecular weight distribution (M
w / Mn) was measured. Table 3 shows the results.

[0047]

[Table 3]

(Note) Mw: weight average molecular weight (× 10 ⁴ ) Mw / Mn: molecular weight distribution Examples 1 to 37 and Comparative Examples 1 to 5 (A) A rubber component comprising the types and amounts shown in Table 4; B)
Ingredients, and carbon black as other compounding agents,
A rubber composition was prepared by blending a softener, zinc white, stearic acid, an antioxidant, a vulcanization accelerator and sulfur. The above rubber composition was used for a side wall portion reinforcing layer to obtain a size 2
A 05 / 60R15 radial tire for passenger cars was manufactured according to a conventional method. The maximum thickness of the side wall reinforcing layer is shown in Table 4 as a reinforcing rubber gauge. The obtained tires were evaluated for ride comfort, run flat durability, and rolling resistance. The results are shown in Table 4.

[0049]

[Table 4]

[0050]

[Table 5]

[0051]

[Table 6]

[0052]

[Table 7]

[0053]

[Table 8]

(Note) Component (A) * 1) Butadiene rubber: "BR01" [cis-1,4-polybutadiene, manufactured by JSR Corporation, vinyl bond content 2.5%] (B) Component * 2) Compound of general formula (I) Compound A of general formula (I): 1,6-bis (N, N'-dibenzylthiocarbamoyldithio) hexane (VULC
UREN TRIAL PRODUCT KA9188
BAYER) Compound B of general formula (I): 1,6-bis (N, N'-dimethylthiocarbamoyldithio) hexane (prototype synthetic product) Compound C of general formula (I): 1,6-bis ( N, N'-diethylthiocarbamoyldithio) hexane (prototype synthesis product) Compound D of general formula (I): 1,6-bis (N, N'-di (2-ethylhexyl) thiocarbamoyldithio) hexane (prototype synthesis) Product) Compound E of general formula (I): 1,6-bis (benzothiazolyldithio) hexane (prototype synthetic product) * 3) Citraconimide compound Citraconimide compound A: PERKALINK 90
0 (trademark, manufactured by FLEXSYS) Citraconimide compound B: N, N'-m-phenylene-biscitraconimide (prototype synthetic product) * 4) Acrylates Acrylates A: KAYARAD D-310 (trademark, Nippon Kayaku ( Acrylates B: KAYARAD DPHA (trademark)
Acrylates C: KAYARAD D-330 (trademark, manufactured by Nippon Kayaku Co., Ltd.)

Other compounding agents * 5) Carbon black: "GPF" [trademark: #Asahi NP
G, manufactured by Asahi Carbon Co., Ltd.) * 6) Softener: Diana Process Oil NP-2
* 4) [trademark, manufactured by Idemitsu Kosan Co., Ltd.] * 7) Zinc flower: No. 3 [trademark, manufactured by Mitsui Mining & Smelting Co., Ltd.] * 8) Stearic acid: "LUNAC RC beads" [trademark, manufactured by Kao Corporation] * 9) Antioxidant: "Nocrack 6C" [trademark, manufactured by Ouchi Shinko Chemical Co., Ltd., N-phenyl-N '-(1,3-
Dimethylbutyl) -p-phenylenediamine] * 10) Vulcanization accelerator: "Noxera-NS" [trademark, N-tert-butyl-2-benzothiazolylsulfenamide manufactured by Ouchi Shinko Chemical Co., Ltd.] * 11) Sulfur “MUCRON-OT” [trademark, manufactured by Shikoku Chemicals Co., Ltd.]

From the above results, it can be seen that the pneumatic tire using the rubber composition having the specific properties of the present invention for the side wall reinforcing layer has a good ride comfort by greatly reducing the gauge of the side reinforcing rubber. It can be seen that the run-flat durability was excellent because the reduction of the elasticity and the rolling resistance at a high temperature could be suppressed, and the reduction of the elastic modulus at a high temperature could be suppressed.

[0057]

From the above results, it can be seen that the pneumatic tire using the rubber composition containing the conjugated diene-based polymer of the present invention for the sidewall reinforcing layer and / or the bead filler has a high ride comfort. It shows that all the performances of run flat durability and rolling resistance are excellent, and particularly when polybutadiene having a vinyl bond amount of 40% or more is used, it has extremely excellent run flat durability. Also,
It is possible to reduce the weight of the tire while maintaining other performances.

[Brief description of the drawings]

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pneumatic tire of the present 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 Rubber reinforcing layer 8 Tread part

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) C08K 5/103 C08K 5/103 5/3415 5/3415 5/40 5/40

Claims (16)

[Claims] 1. A rubber composition comprising a pair of left and right bead cores and a bead filler disposed radially outside of the bead core in a tire radial direction, wherein the rubber composition constituting the bead filler is (A) a conjugated diene unit. A vinyl bond amount of 25% or more and a weight average molecular weight (Mw) of 200,000 to 90
Weight average molecular weight and number average molecular weight (Mn)
And a rubber component containing a conjugated diene-based polymer having a molecular weight distribution (Mw / Mn) of 1 to 4 represented by the following formula: (B) a general formula (I) R ¹ -SSSASS —R ² (I) (where A is an alkylene group having 2 to 10 carbon atoms, R ¹ and R
² independently represents a monovalent organic group containing a nitrogen atom. A pneumatic tire comprising a compound represented by the formula (1), at least one compound selected from citraconimide compounds and acrylate compounds. 2. A carcass layer, a tread portion disposed radially outside the carcass layer in a tire radial direction, a pair of sidewall portions disposed on the left and right sides of the tread portion, and a plurality of sidewall portions disposed on the sidewall portion. A rubber composition comprising a rubber reinforcing layer and the rubber reinforcing layer disposed on the side wall portion comprises: (A) a conjugated diene unit having a vinyl bond content of 25% or more and a weight average molecular weight (Mw) )
Is 200,000 to 900,000, and the molecular weight distribution (Mw / M) represented by the ratio of the weight average molecular weight to the number average molecular weight (Mn).
n) a rubber component containing a conjugated diene polymer having 1 to 4 and (B) a general formula (I) R ¹ -SSSASR ² (I) A represents an alkylene group having 2 to 10 carbon atoms, R ¹ and R
² independently represents a monovalent organic group containing a nitrogen atom. A pneumatic tire comprising a compound represented by the formula (1), at least one compound selected from citraconimide compounds and acrylate compounds. 3. A pair of left and right bead cores, a bead filler and a carcass layer disposed radially outward of the bead core in a tire radial direction, a tread portion disposed radially outward of the carcass layer in a tire radial direction, and a tread portion. A rubber composition comprising a pair of sidewall portions disposed on the left and right sides and a rubber reinforcing layer disposed on the sidewall portions, and a rubber composition constituting the bead filler and a rubber disposed on the sidewall portions. The rubber composition constituting the reinforcing layer is (A)
The vinyl bond amount in the conjugated diene unit is 25% or more, the weight average molecular weight (Mw) is 200,000 to 900,000,
And a rubber component containing a conjugated diene-based polymer having a molecular weight distribution (Mw / Mn) of 1 to 4 represented by a ratio of a weight average molecular weight to a number average molecular weight (Mn), and (B) 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 independently represents a monovalent organic group containing a nitrogen atom. A pneumatic tire comprising a compound represented by the formula (1), at least one compound selected from citraconimide compounds and acrylate compounds. 4. The rubber component (A) has a vinyl bond content of 25% or more in a conjugated diene unit, a weight average molecular weight (Mw) of 200,000 to 900,000, and a weight average molecular weight and a number average molecular weight (Mn). Molecular weight distribution (M
w / Mn) is 1 to 4, and further contains a conjugated diene-based polymer containing a tin atom and / or a nitrogen atom in a molecule. tire. 5. The air according to claim 4, wherein the content of the conjugated diene-based polymer containing a tin atom and / or a nitrogen atom in a molecule is 50% by weight or more of the total amount of the rubber component. Containing tires. 6. The pneumatic tire according to claim 4, wherein all of the rubber component (A) is a conjugated diene-based polymer containing a tin atom and / or a nitrogen atom in a molecule. 7. The pneumatic tire according to claim 1, wherein the conjugated diene-based polymer has a branched structure. 8. The conjugated diene-based polymer is a conjugated diene homopolymer, a conjugated diene copolymer or a conjugated diene-aromatic vinyl copolymer.
A pneumatic tire according to any one of the above. 9. The pneumatic tire according to claim 1, wherein the conjugated diene polymer is a polybutadiene, a styrene-butadiene copolymer, or a modified polymer thereof. 10. A in the general formula (I) of the component (B) is:
The pneumatic tire according to any one of claims 1 to 9, wherein the pneumatic tire is a hexamethylene group. 11. The pneumatic tire according to claim 1, wherein the citraconic imide compound (B) is a biscitraconic imide. 12. The acrylate component (B) is a polyhydric ester of a polyhydric alcohol and acrylic acid or a polyhydric ester of a polyhydric alcohol and acrylic acid or another carboxylic acid. The pneumatic tire according to any one of claims 1 to 11. 13. The compound represented by the general formula (I) as the component (B) is 1,6-bis (N, N′-dibenzylthiocarbamoyldithio) hexane. 13. The pneumatic tire according to any one of claims 12 to 12. 14. The pneumatic tire according to claim 11, wherein the biscitraconimide of the component (B) is 1,6-bis (citraconimidomethyl) benzene. 15. The pneumatic tire according to claim 1, wherein the acrylate as the component (B) is an acyl group-modified dipentaerythritol acrylate. 16. (A) For 100 parts by weight of the rubber component,
The pneumatic tire according to any one of claims 1 to 15, wherein the component (B) is added in an amount of 0.5 to 20 parts by weight.