JP2002079803A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide rubber composition of improved heat resistance and suitable for tire side wall reinforcement rubber or tire bead filler rubber and a pneumatic tire using the same. SOLUTION: A tire is provided with a pair of left and right bead parts, a bead filler and a carcass layer provided in an outside of the bead part in a tire radius direction, a tread part arranged in an outside of the carcass layer in the tire radius direction, a pair of side wall parts provided at left and right of the tread part, and a rubber reinforcement layer provided in the side wall part. At least one of rubber composition constructing the bead filler and rubber composition constructing the rubber reinforcement layer provided in the side wall part includes more than 50 Wt.% of conjugated diene-based polymer in which vinyl bond content exceeds 25% of conjugated diene unit, of which weight average molecular weight (Mw) is 200,000 to 900,000 and of which molecular distribution (Mw/Mn) defined as ratio of weight average molecular weight and number average molecular weight (Mn) is 1 to 4.

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 rubber reinforcing layer provided on a side wall portion. 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, the crosslinked portion formed by vulcanization or the like or the polymer itself constituting the rubber component tends to be cut. For this reason, the elastic modulus of the rubber composition decreases, the deflection of the tire increases, heat generation proceeds, the breaking limit of the side reinforcing layer decreases, and as a result, the tire may fail relatively early. was there.

As one 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 material, or the loss tangent (tan δ) thereof is made as small as possible. A method of setting and suppressing the heat generation of the rubber composition itself is known.However, there is a limit in the approach from the conventional compounding surface, and in run-flat running, in order to ensure a certain endurance distance or more, In reality, it is necessary to increase the amount of the side reinforcing layer and the bead filler, and as a result, unfavorable situations such as deterioration of ride comfort, deterioration of noise level, and increase in weight during normal running are caused.

[0004]

SUMMARY OF THE INVENTION Under such circumstances, the present invention provides a tire having good ride comfort during normal running by devising a rubber component used for a bead filler or a sidewall reinforcing layer. It is an object of the present invention to provide a pneumatic tire that is particularly excellent in run flat durability while maintaining performance at least.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and as a result, have found that a rubber composition containing a specific conjugated diene-based polymer has at least a bead filler and a side reinforcing layer. It has been found that the pneumatic tire used on one side has significantly 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 portions, and a bead filler disposed radially outside the bead portion in the tire radial direction, wherein the rubber composition constituting the bead filler is a conjugated diene unit. When the vinyl bond amount is 25% or more, the weight average molecular weight (M
w) is 200,000 to 900,000, and the molecular weight distribution (Mw / Mw / Mn) is represented by the ratio of the weight average molecular weight to the number average molecular weight (Mn).
An object of the present invention is to provide a pneumatic tire characterized in that a rubber component contains 50% by weight or more of a conjugated diene polymer having Mn) of 1 to 4.

The present invention also provides a carcass layer, a tread portion disposed radially outward of the carcass layer, a pair of sidewall portions disposed on the left and right sides of the tread portion, and A rubber reinforcing layer provided on the side wall portion, the rubber composition constituting the rubber reinforcing layer has a vinyl bond content of 25% or more in the conjugated diene unit and a weight average molecular weight (M
w) is 200,000 to 900,000, and the molecular weight distribution (Mw / Mw / Mn) is represented by the ratio of the weight average molecular weight to the number average molecular weight (Mn).
An object of the present invention is to provide a pneumatic tire characterized in that a rubber component contains 50% by weight or more of a conjugated diene polymer having Mn) of 1 to 4. The present invention further provides a pair of left and right bead portions, a bead filler and a carcass layer disposed radially outward of the bead portion in the tire radial direction, a tread portion disposed radially outward of the carcass layer in the tire radial direction, and the tread. A pair of sidewall portions disposed on the left and right sides of the portion, and a rubber reinforcing layer disposed on the sidewall portion, the rubber composition constituting the bead filler and disposed on the sidewall portion. Both the rubber compositions constituting the rubber reinforcing layer have a conjugated diene unit having a vinyl bond amount of 25% or more and a weight average molecular weight (Mw) of 200,000 to 200,000.
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
A conjugated diene polymer is contained in a rubber component in an amount of 50% by weight or more.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a conjugated diene-based 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 specified range is 50% by weight. In a tire using the rubber composition containing the above as at least one of the bead filler and the side reinforcing layer, the effect of suppressing the decrease in the elastic modulus due to the temperature rise of the rubber composition is remarkable, so that the deflection of the tire due to run flat running increases. Is suppressed, so that the run flat durability can be improved. 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. If the vinyl bond content is less than 25%, the decrease in the elastic modulus due to the sulfur crosslinking cleavage at a high temperature of 150 ° C. or more becomes dominant, so that 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 30%
Or more, and more preferably 35% or more. Especially 4
It is preferably 0 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 tensile properties of the rubber composition,
Rolling resistance is inferior, and when it exceeds 900,000, workability tends to be inferior. In this respect, Mw is preferably from 300,000 to 800,000, and particularly preferably from 300,000 to 700,000.

Further, the molecular weight distribution (Mw /
Mn) needs to be 1 to 4. If it exceeds 4, the exothermicity tends to decrease and it becomes difficult to maintain the elastic modulus in a temperature region of 150 ° C. or more. 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, as the conjugated diene monomer, for example, 1,3
-Butadiene, 1,3-pentadiene, 1,3-hexadiene and the like, among which 1,3-butadiene is preferable. Examples of the aromatic vinyl monomer used for copolymerization with a conjugated diene monomer include, for example, styrene, α-
Methylstyrene, 1-vinylnaphthalene, 3-vinyltoluene, ethylvinylbenzene, divinylbenzene, 4
-Cyclohexylstyrene, 2,2,6-tolylstyrene and the like, among which styrene is preferred.

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, sec-butyllithium, ethyllithium, nlithium -Propyl lithium, tert-octyl lithium, phenyl lithium and the like, and preferred is n-butyl lithium. These organic lithium initiators may be used alone or as a mixture of two or more. The amount of vinyl bond in the conjugated diene unit is determined by the following formulas: ditetrahydrofurylpropane, tetrahydrofuran, diethyl ether, dimethoxybenzene, dimethoxyethane, ethylene glycol dibutyl ether, triethylamine, pyridine, N, N, N ', N'-tetramethylethylenediamine, It can be changed as appropriate by adding an appropriate amount of an ether such as peridinoethane and a 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-containing rubber composition. In particular, those having a branched structure obtained by using a polyfunctional modifier are preferred. The above-mentioned 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 chloride, dioctyltin dichloride, dibutyltin dichloride, triphenyltin chloride, and a nitrogen atom is an isocyanate compound such as diisocyanatodiphenylmethane or 4- (dimethyl). Amino) benzophenone compounds such as benzophenone, nitrogen-containing compounds such as 4-dimethylaminobenzylideneaniline, dimethylimidazolidinone, and N-methylpyrrolidone.

Also, a modified polymer can be obtained 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. it can. The conjugated diene-based polymer in the present invention has a vinyl bond content of 2 in the conjugated diene unit.
5% or more, weight average molecular weight (Mw) of 200,000 to 900,000,
It is a conjugated diene polymer having a molecular weight distribution (Mw / Mn) represented by a ratio of a weight average molecular weight to a number average molecular weight (Mn) of 1 to 4 and containing a tin atom and / or a nitrogen atom in a molecule. Is preferred. In the present invention, as the conjugated diene-based polymer, polybutadiene and a styrene-butadiene copolymer rubber, in particular, polybutadiene are preferable, and the above-mentioned modified polymers are particularly preferable.

In the pneumatic tire of the present invention, the modified polymer as the rubber component of the bead filler or the rubber reinforcing layer of the sidewall portion is preferably contained in an amount of 40% by weight or more based on the total amount of the conjugated diene polymer. . The rubber composition of the present invention comprises the aforementioned polymer in a rubber component in an amount of 5%.
It is necessary to contain 0% 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. From this point, the polymer is not less than 60% by weight,
Further, it is preferably contained at 80% by weight or more. In the rubber composition of the present invention, other rubber components that can be mixed with the polymer are not particularly limited, and include, for example, natural rubber, polyisoprene synthetic rubber (IR); cis-1,4
-Polybutadiene rubber (BR), styrene-butadiene rubber (SBR), acrylonitrile butadiene rubber (N
BR), chloroprene rubber (CR), butyl rubber (II
R) and the like. These rubbers may be used in combination of two or more.

In the rubber composition containing the conjugated diene polymer according to the present invention, in addition to the above components, vulcanizing agents such as sulfur and peroxide, vulcanization accelerators and the like usually used in the rubber industry, Various compounding agents such as an antioxidant, a softener, a reinforcing filler, and an inorganic filler can be appropriately contained. Further, the rubber composition of the present invention further includes particles of various materials,
It may be a composite with fiber, cloth and the like. 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 disposed on a sidewall portion.

Next, with respect to the pneumatic tire of the present invention,
This will be described with reference to the accompanying drawings. FIG. 1 is a partial cross-sectional view of the left half of an example of the pneumatic tire of the present invention. The pneumatic tire 1 has a pair of left and right ring-shaped beads 4, and a radially outer side of the beads 4. Carcass layer 2 composed of at least one ply in which a plurality of cords arranged in parallel are embedded in a covering rubber.
A belt layer 3 disposed radially outward of the carcass layer 2 in the tire radial direction; a tread portion 8 disposed radially outward of the belt layer 3 in the tire radial direction; And a rubber reinforcing layer 7 provided on the side wall portion 6.

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 portion 4 to form a folded end portion. Bead filler 5
Is located between the folded carcass ply 2a and its folded end, and the down carcass ply 2b
Is the side wall portion 6 and the folded carcass ply 2a
And between the folded end portions. Rubber reinforcement layer 7
Are arranged on the inner peripheral surface of the sidewall portion of the folded carcass ply 2a. Side wall part 6
The rubber of the rubber reinforcing layer 7 for reinforcing the rubber 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 by using the rubber composition containing the conjugated diene polymer. In the pneumatic tire of the present invention, ride comfort and noise level do not substantially deteriorate due to an 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 rubber reinforcing layer of the bead portion or the side wall portion has a significantly improved durability, particularly in run-flat running, and can significantly extend the running distance. it can.

[0017]

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 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 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) Ride Comfort Each prototype tire is mounted on a passenger car, and a ride comfort feeling test is carried out 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 is rim-assembled at normal pressure, filled with an internal pressure of 200 kPa, and then left at room temperature of 38 ° C. for 24 hours. The core of the valve is removed, and the internal pressure is set to atmospheric pressure. 4kN (5
A drum running test was performed under the conditions of 50 kg), 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 was defined as run flat durability, and Examples 1 to 21 were expressed by an index with Comparative Example 1 being 100.
23 to 23 are represented by indices with Comparative Example 2 being 100, Examples 24 to 27 are represented by indices with Comparative Example 3 being 100, and Examples 28 to 31 and Comparative Examples 4 and 5.
Is represented by an index with Comparative Example 6 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 Comparative Example 1 as a control,
For Examples 22 to 23, Comparative Example 2 was used as a control, for Examples 24 to 27, Comparative Example 3 was used as a control, and for Examples 28 to 31, and Comparative Examples 4 and 5, Comparative Example 6 was used as a control. The index was expressed as an index with the control of 100 as 100. The smaller the index,
Rolling resistance is small.

Production Examples 1 to 18 (BR polymers A, B, I
~ X) 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 and nitrogen-substituted temperature-adjusting jacket, and 4.5.
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%.

In this polymerization system, SnCl4 is used as a modifier.
0.11 ml of a 1M cyclohexane solution was added, followed by a denaturation reaction for 30 minutes. After that,
0.5 ml of a 5% solution of 6-di-t-butyl-p-cresol (BHT) in isopropanol was added to stop the reaction, and the polymer was dried by a conventional method to obtain a weight product A. Polymers B and I to X were obtained in the same manner as described above, except that the amounts of BuLi and DTHFP and the types and amounts of the modifiers were changed to those shown in Table 1. The resulting modified polybutadiene polymers A, B, and I to X had a microstructure (vinyl bond amount), molecular weight (Mw), and molecular weight distribution (Mw / M).
n) was measured. Table 1 shows the results.

Production Examples 19 to 21 (BR polymers Y, Z,
AA) 3 kg of cyclohexane, 500 g of butadiene monomer and 1.6 mmol of ditetrahydrofurylpropane (DTHFP) were injected into an 8 liter pressure-resistant reactor equipped with a dried, nitrogen-substituted temperature-adjusting jacket, and 4 mmol of the same.
Of n-butyllithium (BuLi), 4.2 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 without any precipitation from the start to the end of the polymerization. The polymerization conversion was almost 100%. To this polymerization system was added 0.11 ml of a 1 M cyclohexane solution of SnCl4 as a denaturing agent, followed by a denaturation reaction for 30 minutes. Thereafter, 2,6-di-t-butyl-p is added to the polymerization system.
-The reaction was stopped by adding 0.5 ml of a 5% solution of cresol (BHT) in isopropanol, and the polymer was dried by a conventional method to obtain a weight Y. Polymers Z and AA were prepared in the same manner as described above except that the amounts of BuLi and DTHFP and the types and amounts of modifiers were changed to those shown in Table 1.
I got Obtained modified polybutadiene polymer Y, Z, A
The microstructure (vinyl content), molecular weight (Mw) and molecular weight distribution (Mw / Mn) of A were measured. Table 1 shows the results.

[0022]

[Table 1]

(Notes) 1) Mw: Weight average molecular weight Mw / Mn: Molecular weight distribution 2) Modifier TTC: Tin tetrachloride (SnCl4) TBTC: Tributyltin (Bu3 SnCl) DOTDC: Dioctyltin dichloride (Oct2 S)
nCl2) DBTDC: dibutyltin dichloride (Bu2 SnC
12) TEOSDI: N- (3-triethoxysilylpropyl)
-4,5-dihydroimidazole DMABP: 4- (dimethylamino) benzophenone DMABA: 4-dimethylaminobenzylideneaniline DMABB: 4-dimethylaminobenzylidenebutylamine

Embedded image DMI: dimethylimidazolidinone

Embedded image NMP: N-methylpyrrolidone

Embedded image S340: N- (1,3-dimethylbutylidene) -3-
(Triethoxysilyl-1-propanamine

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 22 to 27 (BR polymers C to H) A 15 mol% cyclohexane solution of continuously dried butadiene was placed in an 8 liter pressure-resistant reactor equipped with a dried, nitrogen-purged, temperature-adjusting jacket. Introduced at a rate of 200 g per minute. From the same port, ditetrahydrofurylpropane (DTHFP) as a cyclohexane solution (1 mol / l) was added at 0.03 mmol / min.
And 0.3 mmo of n-butyllithium (BuLi) as an n-hexane solution (4.5 mmol / liter).
It was introduced continuously at a rate of 1 / min. The polymerization system is always kept at 80 ° C., and the produced polymer is continuously taken out from the upper part of the reactor and poured into a 5% solution of 2,6-di-t-butyl-p-cresol (BHT) in isopropanol to give a polymer. I got The polymerization system was uniform and transparent without any precipitation from the start to the end of the polymerization. The polymerization conversion rate is
It was almost 100%. The obtained polymer solid was dried to obtain a rubbery polymer C. In addition, except that the introduction rates (mmol / min) of BuLi and DTHFP were changed to those shown in Table 2, polymers D to
H was obtained. Microstructure (vinyl bond amount), molecular weight (Mw), and molecular weight distribution (Mw / Mn) of the obtained polybutadiene polymers C to H were measured. Table 2 shows the results.

[0025]

[Table 2] (Note) Mw: Weight average molecular weight Mw / Mn: Molecular weight distribution

Production Examples 28 to 31 (SBR-based polymers BA to
BD) Into an 8 liter pressure-resistant reactor equipped with a dried, nitrogen-substituted temperature-adjusting jacket, cyclohexane 3 kg, butadiene monomer 475 g, styrene 25 g, 2.5 mmol
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 uniform and transparent without any precipitation from the start to the end of the polymerization. The polymerization conversion was almost 100%.
After 5 ml of a 1 M cyclohexane solution of c-MDI was further added to the polymerization system, a denaturation reaction was performed for 30 minutes. Thereafter, 0.5 ml of a 5% solution of 2,6-di-t-butyl-p-cresol (BHT) in isopropanol was added to the polymerization system to terminate the reaction, and the polymer was dried in a conventional manner to obtain a polymer BA. I got 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 production method of the above-mentioned polymers BA and BB, polymers BC and BD were produced in the same manner as above except that c-MDI as a modifier was not added.
I got The microstructure (vinyl bond amount), molecular weight (Mw), and molecular weight distribution (Mw / Mn) of the resulting modified or unmodified styrene-butadiene polymers BA to BD were measured. Table 3 shows the results.

Production Examples 32-33 (SBR polymer BE,
BF) Into an 8 liter pressure-resistant reactor equipped with a dried, nitrogen-substituted temperature-adjusting jacket, 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 milate in cyclohexane 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 without any precipitation from the start to the end of the polymerization. The polymerization conversion is approximately 1
00%. Isopropanol was added to the polymerization system to stop the reaction, and the polymer solid was dried by a conventional method to obtain a polymer BE. Further, in the above method for producing polymer BE, except that the amounts of butadiene and styrene were changed to those shown in Table 3, polymer BF was produced in the same manner as described above.
I 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.

[0028]

[Table 3] (Note) 1) Mw: weight average molecular weight Mw / Mn: molecular weight distribution 2) modifier c-MDI: crude MDI / M made by Nippon Polyurethane
R400

Examples 1 to 21 and Comparative Example 1 60.0 parts by weight of carbon black GPF (trademark; #NPG, manufactured by Asahi Carbon Co., Ltd.) based on 100 parts by weight of the rubber component having the types and amounts shown in Table 4 Part, softener "Diana Process Oil NP-24" [trademark, Idemitsu Kosan Co., Ltd.
3.0 parts by weight, Zinhua No. 3 [trademark, manufactured by Mitsui Mining & Smelting Co., Ltd.] 5.0 parts by weight, stearic acid "LUNAC"
RC beads "[trademark, manufactured by Kao Corporation] 1.0 part by weight, anti-aging agent" Nocrack 6C "[trademark, manufactured by Ouchi Shinko Chemical Co., Ltd., N-phenyl-N '-(1,3- Dimethylbutyl) -p-phenylenediamine] 2.0 parts by weight, vulcanization accelerator "Noxera-NS" (trademark, manufactured by Ouchi Shinko Chemical Co., Ltd., N-tert-butyl-2-benzothiazolylsulfen) Amide] 2.5 parts by weight and sulfur “MUC
RON-OT "(trademark, manufactured by Shikoku Chemicals Co., Ltd.) in an amount of 3.0 parts by weight to prepare a rubber composition. The above rubber composition was used for a side wall portion reinforcing layer to obtain a size of 225 /
A 55R17 radial tire for a passenger car was manufactured according to a conventional method, and the tire was evaluated for riding comfort, run flat durability, and rolling resistance. The maximum thickness of the sidewall reinforcing layer is shown in Table 4 as a reinforcing rubber gauge. The results are shown in Table 4.

[0030]

[Table 4] (Note) Butadiene rubber BR01: cis-1,4-polybutadiene (trade name "BR01", manufactured by JSR Corporation)

Examples 22 to 27 and Comparative Examples 2 and 3 The same procedures as in Example 1 were carried out except that the rubber components having the types and amounts shown in Table 5 and 6.0 parts by weight of sulfur were used. A rubber composition was prepared in the same manner. Using this rubber composition for the side wall portion reinforcing layer, a tire was manufactured in the same manner as in Example 1, and the tire was evaluated for ride comfort, run flat durability, and rolling resistance. The results are shown in Table 5.

[0032]

[Table 5] (Note) Butadiene rubber BR01: See above

Examples 28 to 31 and Comparative Examples 4 to 6 Rubber compositions were prepared in the same manner as in Example 1 except that the rubber compositions having the types and amounts shown in Table 6 were used. A tire similar to that of Example 1 was manufactured using this rubber composition as a sidewall reinforcing layer and a bead filler, and the same evaluation as that of Example 1 was performed on the tire. The results are shown in Table 6.

[0034]

[Table 6]

(Note) 1) Butadiene rubber BR01: 2) Applicable member: Each rubber composition shown in Table 6 is applied. From the above results, the pneumatic tire using the specific-property polybutadiene or styrene-butadiene copolymer rubber composition of the present invention for the sidewall reinforcing layer or the bead filler has a riding comfort and run flat durability. It shows that all the performances of 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.
Further, it is possible to reduce the weight of the tire while maintaining other performances.

[0036]

According to the present invention, a rubber composition obtained by blending a conjugated diene polymer having a specific property is used for a sidewall reinforcing rubber for a tire and / or a bead filler rubber for a tire. Pneumatic tires have excellent ride comfort, run flat durability, and rolling resistance, and are particularly excellent in durability in run flat running, and can significantly extend the running distance.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view of an example of a pneumatic tire according to 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 portion 5 Bead filler 6 Side wall portion 7 Rubber reinforcing layer 8 Tread portion

Claims (13)

[Claims] 1. A rubber composition comprising a pair of left and right bead portions and a bead filler disposed radially outside the bead portion in a tire radial direction, wherein the rubber composition constituting the bead filler is a vinyl compound in a conjugated diene unit. 25% binding
As described above, the weight of 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 the ratio of the weight average molecular weight to the number average molecular weight (Mn) of 1 to 4 A pneumatic tire characterized by containing 50% by weight or more of the coalesced rubber component. 2. A carcass layer, a tread portion disposed radially outside of the carcass layer in a tire radial direction, a pair of sidewall portions disposed on left and right sides of the tread portion, and a plurality of sidewall portions disposed on the sidewall portion. The rubber composition that comprises a rubber reinforcing layer and is provided on the sidewall portion has a vinyl bond content of 25% or more in the conjugated diene unit and a weight average molecular weight (Mw) of 20.
And the molecular weight distribution (Mw / Mn) represented by the ratio of the weight average molecular weight to the number average molecular weight (Mn) is 1
A pneumatic tire characterized in that the rubber component contains at least 50% by weight of the conjugated diene-based polymer of No. 4 to No. 4. 3. A pair of left and right bead portions, a bead filler and a carcass layer disposed outside the bead portion in the tire radial direction, a tread portion disposed outside the carcass layer in the tire radial direction, and the tread. A pair of sidewall portions disposed on the left and right sides of the portion, and a rubber reinforcing layer disposed on the sidewall portion, the rubber composition constituting the bead filler and disposed on the sidewall portion. The rubber composition constituting the rubber reinforcing layer has a vinyl bond content of 25% or more in the 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). A pneumatic tire comprising a rubber component containing 50% by weight or more of a conjugated diene-based polymer having a molecular weight distribution (Mw / Mn) represented by a ratio of 1 to 4 in a rubber component. 4. The pneumatic tire according to claim 1, wherein the conjugated diene polymer has a weight average molecular weight (Mw) of 300,000 to 800,000. 5. The pneumatic tire according to claim 1, wherein the conjugated diene polymer has a weight average molecular weight (Mw) of 300,000 to 700,000. 6. The pneumatic tire according to claim 1, wherein a vinyl bond amount is 30% or more. 7. The rubber component according to claim 1, wherein the conjugated diene-based polymer is contained in an amount of 60% by weight or more.
The pneumatic tire according to any one of the above. 8. The pneumatic tire according to claim 1, wherein the rubber component contains a conjugated diene-based polymer containing a tin atom and / or a nitrogen atom in a molecule. 9. The conjugated diene-based polymer has a vinyl bond content in the conjugated diene unit of 25% or more, a weight average molecular weight (Mw) of 200,000 to 900,000, and a ratio of weight average molecular weight to number average molecular weight (Mn). The molecular weight distribution (Mw /
The pneumatic tire according to any one of claims 1 to 8, wherein Mn) is 1 to 4, and contains a conjugated diene-based polymer containing a tin atom and / or a nitrogen atom in a molecule. 10. The method according to claim 1, wherein the content of the conjugated diene-based polymer containing a tin atom and / or a nitrogen atom in the molecule is 40% by weight or more of the total amount of the conjugated diene-based polymer. The pneumatic tire according to any one of the above. 11. The rubber composition according to claim 1, wherein the rubber component contains a conjugated diene polymer having a branched structure.
0. The pneumatic tire according to any one of 0. 12. The pneumatic device according to claim 1, wherein the conjugated diene-based polymer is a conjugated diene homopolymer and / or a conjugated diene-aromatic vinyl copolymer. tire. 13. The pneumatic tire according to claim 1, wherein the conjugated diene polymer is polybutadiene.