JP2001192503A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire exhibiting high-level grip performances on dry, wet, icy and snowy road surfaces. SOLUTION: The pneumatic tire employs for a tread an expanded rubber composition comprising (A) 100 pts.wt. of a rubber component comprising a diene-based rubber and, incorporated thereinto, (B) 0.1-30 pts.wt. of at least one nitrogen-containing compound selected from the group consisting of specific lactams, specific imidazoles, specific ureas and specific pyrrolidones, (C) 0.1-50 pts.wt. of a protonic acid and/or a phenol derivative and (D) a blowing agent and a blowing aid.

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 pneumatic tire having improved grip performance using a rubber composition comprising a tread rubber and a nitrogen-containing compound having a specific structure. For entering tires.

[0002]

2. Description of the Related Art In recent years, consciousness for safety has been increased with the improvement of high kinetic performance and high horsepower of automobiles and maintenance of expressways. In particular, grip performance typified by acceleration performance and braking performance is an important required characteristic. For this reason, conventionally, a technique in which the tread rubber composition itself is devised in order to improve grip on dry and wet road surfaces of a general road is known. As the first method, there is a method using a styrene-butadiene copolymer rubber having a high glass transition temperature and a high styrene content. In this case, as the rubber temperature increases due to running, tan δ decreases, and grip performance decreases. There is a disadvantage of doing so. As a second method, there is a method of securing grip performance by increasing the tan δ of the rubber by filling the processing oil and carbon black at a high level. However, it is difficult to obtain a high level of grip performance due to the limitation of high filling. Further, as a third method, by blending a specific nitrogen-containing compound, t
There is also an attempt to increase an δ and improve grip performance (Japanese Patent Application Laid-Open No. Hei 9-71686). However,
Each of the above-mentioned methods improves grip on dry and wet road surfaces, but does not provide the effect of improving braking performance and driving performance (ice and snow performance) on ice and snow.

On the other hand, as a method for improving the ice and snow performance, a method of using a polymer having a low glass transition temperature to increase the contact area by the softness of the rubber at a low temperature, or a method of blending a foreign substance with the rubber to improve the snow and snow. There are known a method utilizing a scratching effect and a method of obtaining a grip performance by removing a water film on ice and snow by pores on the tread surface using foamed rubber or the like. However, in this case,
Even though the grip performance required for current studless tires can be satisfied to some extent, it has been difficult to ensure high grip performance on ice, snow, dry and wet road surfaces in a well-balanced manner.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a pneumatic tire which satisfies a high level of grip performance on a dry road surface, a wet road surface and an icy road surface under such circumstances. is there.

[0005]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventor has found that a foamed rubber composition containing a nitrogen-containing compound having a specific structure and a protonic acid is used for a tire tread. To achieve that purpose. That is, the present invention relates to (A) 100 parts by weight of a rubber component containing a diene rubber and (B) a general formula (1)

[0006]

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[Wherein, R₁And R_TwoAre independent of each other
Hydrogen atom, alkyl group having 1 to 8 carbon atoms, or unsubstituted
Or a phenyl group having an alkyl group having 1 to 8 carbon atoms.
You. R ₁And R_TwoEven if they are the same or different
Good. And the number of carbon atoms of the heterocyclic ring is 4-1.
9 lactams, general formula (II)

[0008]

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[Wherein, R_ThreeAnd R_FourAre independent of each other
Hydrogen atom, alkyl group having 1 to 8 carbon atoms, or unsubstituted
Or a phenyl group having an alkyl group having 1 to 8 carbon atoms.
You. R _ThreeAnd R_FourEven if they are the same or different
Good. Represented by the general formula (III):

[0010]

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[In the formula, R _{5 to} R ₈ each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an unsubstituted or phenyl group having an alkyl group having 1 to 8 carbon atoms. R _{5 to} R ₈ may be the same or different. At least one nitrogen-containing compound selected from the group consisting of ureas and pyrrolidones represented by the formula:
To 30 parts by weight, (C) 0.1 to 50 parts by weight of a protonic acid and / or phenol derivative, and (D) a foamed rubber composition obtained by blending a foaming agent and a foaming aid in a tread. A pneumatic tire is provided.

[0012]

DETAILED DESCRIPTION OF THE INVENTION (A) used in the present invention
As the diene rubber as a component, a diene synthetic rubber or a mixture of a diene synthetic rubber and a natural rubber is used.
Here, as the diene-based synthetic rubber, for example, polyisoprene synthetic rubber (IR), 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 alone or in combination of two or more.

In the rubber composition according to the present invention, (B)
The nitrogen-containing compound as a component is a lactam having a heterocyclic structure represented by the formula (I). Where R ₁
And R ₂ each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an unsubstituted or phenyl group having an alkyl group having 1 to 8 carbon atoms. The alkyl group may be linear or branched. For example, methyl group, ethyl group, n-propyl group, isopropyl group, n
-Butyl group, isobutyl group, sec-butyl group, t-butyl group, pentyl group, hexyl group, octyl group and the like. Of these, ゜ and R ₁ and R ₂ are preferably hydrogen or an alkyl group having 3 or less carbon atoms. Also,
The heterocyclic ring preferably has 4 to 12 carbon atoms. Among such lactams, ω-laurolactam is particularly preferred. The imidazole of the component (B) used in the present invention has the structure of the above formula (II). here,
R ₃ and R ₄ each independently represent a hydrogen atom, a carbon number of 1 to 8;
Or an unsubstituted or phenyl group having an alkyl group having 1 to 8 carbon atoms, and the alkyl group may be linear or branched. Among them, R
₃ and R ₄ are preferably hydrogen or an alkyl group having 1 to 3 carbon atoms. Among such imidazoles,
2-Methylimidazole is particularly preferred.

The ureas of the component (B) used in the present invention have the structure of the above formula (III). Here, R _{5 to} R ₈ each independently represent a hydrogen atom, a carbon atom 1
And represents an unsubstituted or phenyl group having an alkyl group having 1 to 8 carbon atoms. The alkyl group may be linear or branched. Among them, R _{5 to} R ₈ are preferably hydrogen or an alkyl group having 1 to 3 carbon atoms. Among such ureas, dimethyl urea is particularly preferred. As the pyrrolidone of the component (B) used in the present invention, a pyrrolidone such as 2-pyrrolidone is preferable. The nitrogen-containing compound as the component (B) may be used alone or in combination of two or more.
Further, in the tread rubber of the tire of the present invention, since the tan δ of the rubber varies depending on the type of the nitrogen-containing compound to be compounded, the high level of ice and snow performance is maintained, and for example, the grip on dry road surfaces is particularly important. If so,
1-benzyl-2-methylimidazole and dimethyl urea are preferably used, and when importance is placed on grip on wet road surfaces, ω-laurolactam and pyrrolidone are preferably used.

The compounding amount of the nitrogen-containing compound is as follows:
0.1 to 30 parts by weight with respect to 00 parts by weight. 0.1
If the amount is less than 10 parts by weight, there is no effect of increasing the tan δ of the rubber, so that the effect of grip performance cannot be obtained. If the amount is more than 20 parts by weight, the effect of addition is small and it is economically disadvantageous. Considering the grip performance and economy, the compounding amount of this nitrogen-containing compound is 0.1%.
The content is preferably 5 to 20 parts by weight, more preferably 2 to 10 parts by weight. Next, the protonic acid of the component (C) used in the present invention is not particularly limited. Examples of the protonic acid include aliphatic monocarboxylic acids such as acetic acid, propionic acid and oleic acid, succinic acid and maleic acid. Aromatic monocarboxylic acids such as aliphatic dicarboxylic acid, benzoic acid, p-methoxybenzoic acid, p-chlorobenzoic acid, p-nitrobenzoic acid, cinnamic acid, naphthoic acid, phthalic acid, phthalic anhydride, and trimellitic acid Protonic acids such as aromatic polycarboxylic acids such as pyromellitic acid and the like are preferable, and among them, naphthoic acids and benzoic acids are particularly preferable. Also, (C)
As the phenol derivative as a component, a phenol-based antioxidant is preferable, and a bisphenol-based antioxidant is particularly preferable.

These proton acids and phenol derivatives as component (C) may be used alone or in combination of two or more. Further, the rubber containing these protonic acids and / or phenol derivatives has different tan δ depending on the type of the rubber. Therefore, while maintaining a high level of ice and snow performance, for example, the grip on dry road surfaces is particularly important. In this case, benzoic acid and naphthoic acid are preferably used, and when importance is placed on the grip of a wet road surface, triethylene glycol-bis [3- (3-t-butyl-
5-methyl-4-hydroxyphenyl) propionate] [trade name: IRGANO, manufactured by Ciba-Geigy Japan Ltd.]
X245], 4,4'-thio-bis (6-tert-butyl-3-methylphenol) [manufactured by Ouchi Shinko Chemical Co., Ltd., trademark: Nocrack 300] and 4,4'-butylidenebis (3-methyl -6-tert-butylphenol) [Ouchi Shinko Chemical Industry Co., Ltd., trademark; NS-3
0] and the like are preferably used. Therefore, in the present invention, it is possible to obtain a high level of steering stability on dry road surfaces (dry steering stability) and steering stability on wet road surfaces (wet steering stability) while maintaining high performance on ice. It is possible. Protonic acid as component (C) and / or
Alternatively, the compounding amount of the phenol derivative is 0.1 to 50 parts by weight, preferably 0.5 to 20 parts by weight based on 100 parts by weight of the rubber component. If the amount is less than 0.1 part by weight, the effect of the grip performance cannot be obtained because the effect of increasing tan δ of the rubber is not obtained even when used in combination with the nitrogen-containing compound. In order to obtain sufficient grip performance, the amount of the protonic acid and / or phenol derivative is preferably 1 to 1.5 times the amount of the nitrogen-containing compound.

Further, the rubber composition applied to the tread of the tire of the present invention is made of foamed rubber, and therefore, it is necessary to incorporate a foaming agent and a foaming aid as the component (D). Examples of the foaming agent include dinitrosopentamethylenetetraamine (DPT), azodicarbonamide (ADCA), dinitrosopentastyrenetetramine, benzenesulfonylhydrazide derivative, p, p'-oxybisbenzenesulfonylhydrazide (OBSH) , Sulfonyl hydrazides such as p-toluenesulfonyl hydrazide (TSH), ammonium bicarbonate, nitrososulfonyl azo compounds, N,
N'-dimethyl-N, N'-dinitrosophthalamide,
p-toluenesulfonyl semicarbazide and p, p'-
Oxy-bis (benzenesulfonyl semicarbazide) and the like. One of these may be used alone, or two or more of them may be used in combination, and may be appropriately selected and used depending on the vulcanization temperature and the like. Among these foaming agents, azodicarbonamide (ADCA) is preferable in consideration of various properties such as manufacturing processability.

In the present invention, examples of the foaming auxiliary used in combination with the foaming agent include auxiliaries used in the production of ordinary foamed products such as urea, zinc stearate, metal salts of benzenesulfinic acid and zinc white. No. These are 1
Species may be used alone or in combination of two or more. Among these, sodium benzenesulfinate alone or a combination thereof with urea is particularly preferred. The foaming ratio of the tread rubber using the rubber composition in the present invention is preferably from 10 to 40%. Vs is calculated by the following equation. If it is less than 10%, the effect of removing the water film is reduced and the ice and snow performance is poor, and if it exceeds 40%, the abrasion resistance tends to be poor. Considering ice and snow performance and wear resistance,
Further, 15 to 30% is preferable. Vs = {(ρ ₀ / ρ ₁ ) −1} × 100 (%)

Here, ρ ₁ is the density (g / cm ³ ) of the vulcanized rubber (foamed rubber), and ρ ₀ is the density (g / cm ³ ) of the solid phase in the vulcanized rubber (foamed rubber). ). In addition, these densities are calculated from the weight in ethanol and the weight in air, respectively. In the rubber composition according to the present invention, carbon black, a process oil, a vulcanizing agent, a vulcanization accelerator, an antioxidant, which are usually used in the rubber industry, as long as the object of the present invention is not impaired. A scorch inhibitor, zinc white, stearic acid and the like may be added. The composition can be obtained by kneading using a kneading machine such as a roll or an internal mixer. The pneumatic tire of the present invention is manufactured by a usual method using the above rubber composition as a tread rubber. The pneumatic tire of the present invention thus obtained exhibits excellent performance in all of on-ice performance, dry steering stability, and wet steering stability.

[0020]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. In addition, the grip performance of the tire was performed by each evaluation of the performance on ice, dry steering stability, and wet steering stability by the following methods. (1) Performance on ice Running on a flat road with an ice temperature of -5 ° C at 20k / h
At the time of m / hr, the brake was depressed to lock the tire, and the distance to the stop was measured. The result was expressed as an index with the reciprocal of the distance taken as 100 for the comparative tire. The larger the value, the better the braking performance on ice. (2) Dry steering stability and wet steering stability Each prototype tire was mounted on a passenger car by a specialized driver and allowed to run on a circuit on a dry or wet road surface, and a lap time (second) at that time was measured. Comparative example 1
The tire is shown in an exponential expression with the tire being 100, and the larger the value, the better.

Examples 1 to 7 and Comparative Examples 1 to 3 As shown in Table 1, a blend of natural rubber and polybutadiene (cis-1,4-polybutadiene) was used as a rubber component, and a nitrogen-containing compound of component (B) was used. Each of the rubber compositions was prepared by changing the types of the protonic acid and the phenol derivative as the component (C), and the rubber compositions were applied to a tread rubber to produce a prototype 185 / 70R14 radial tire for a passenger car by an ordinary method. For each tire obtained, performance on ice,
Dry steering stability and wet steering stability were evaluated.
Further, the foaming ratio of each vulcanized rubber composition was measured by the method described above. The results are shown in Table 1.

[0022]

[Table 1]

[Note] * 1) N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine * 2) 2,2,4-trimethyl-1,2-dihydroquinoline polymer * 3 ) N-cyclohexyl-2-benzothiazyl-sulfenamide * 4) ADCA; azodicarbonamide * 5) BSN; sodium benzenesulfinate * 6) Nitrogen-containing compound A; 1-benzyl-2-methylimidazole B; dimethylurea C Ω-laurolactam * 7) Protonic acid or phenolic derivative D; α-naphthoic acid (protic acid) E; 4,4′-butylidenebis (3-methyl-6-te)
rt-butylphenol) (phenolic derivative)

From the results in Table 1, it is found that the first embodiment according to the present invention is
Nos. To 7 are excellent in all of on-ice performance, dry steering stability and wet steering stability. Further, among the examples, ω-laurolactam of component (B) and (C)
Component 4,4'-butylidenebis (3-methyl-6-t
tert-butylphenol) is particularly excellent in wet steering stability, and the component (B) 1
-Benzyl-2-methylimidazole and α of component (C)
-When naphthoic acid was used, it was found that dry handling stability was particularly excellent.

[0025]

The present invention uses a foamed rubber composition containing a specific nitrogen-containing compound and a protonic acid and / or a phenol derivative as a tire tread rubber. A pneumatic tire that satisfies a high level of grip performance on both a road surface and an ice-snow road surface can be obtained.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) C08K 5/095 C08K 5/095 5/13 5/13 5/21 5/21 5/23 5/23 5 / 3412 5/3412 5/3415 5/3415 5/3445 5/3445 5/41 5/41

Claims (10)

[Claims] 1. A rubber component 10 containing (A) a diene rubber
With respect to 0 parts by weight, (B) general formula (1) [Wherein, R ₁ and R ₂ are each independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or unsubstituted or
A phenyl group having an alkyl group of 8 is shown. R ₁ and R
₂ may be the same or different. A lactam represented by the formula (II), wherein the heterocyclic ring has 4 to 19 ring carbon atoms: Wherein R ₃ and R ₄ are each independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or unsubstituted or 1 to 3 carbon atoms.
A phenyl group having an alkyl group of 8 is shown. R ₃ and R
₄ may be the same or different. Represented by the general formula (III): [Wherein, R _{5 to} R ₈ are each independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or unsubstituted or 1 to 8 carbon atoms.
A phenyl group having an alkyl group. R _{5 to} R ₈ may be the same or different. ] 0.1 to 30 parts by weight of at least one nitrogen-containing compound selected from the group consisting of ureas and pyrrolidones represented by
(C) Protonic acid and / or phenol derivative 0.1 to
A pneumatic tire, characterized by using a foamed rubber composition obtained by mixing 50 parts by weight and (D) a foaming agent and a foaming aid in a tread. 2. The pneumatic tire according to claim 1, wherein the lactam of the component (B) is ω-laurolactam. 3. The pneumatic tire according to claim 1, wherein the imidazole as the component (B) is 1-benzyl-2-methylimidazole. 4. The pneumatic tire according to claim 1, wherein the urea component (B) is dimethyl urea. 5. The pneumatic tire according to claim 1, wherein the pyrrolidone as the component (B) is pyrrolidone. 6. The component (C) wherein the protonic acid is acetic acid, succinic acid, oleic acid, rosin acid, maleic acid, benzoic acid,
at least one compound selected from the group consisting of p-methoxybenzoic acid, p-chlorobenzoic acid, p-nitrobenzoic acid, cinnamic acid, phthalic acid, trimellitic acid, pyromellitic acid, phthalic anhydride and naphthoic acid The pneumatic tire according to claim 1, wherein 7. The pneumatic tire according to claim 6, wherein the phenol derivative as the component (C) is a phenolic antioxidant. 8. The pneumatic tire according to claim 7, wherein the phenolic antioxidant as the component (C) is a bisphenol antioxidant. 9. The pneumatic tire according to claim 1, wherein the foaming agent of the component (D) is azodicarbonamide. 10. The pneumatic tire according to claim 1, wherein the foaming aid of the component (D) is sodium benzenesulfinate.