JP2000239442A - Rubber composition and pneumatic tire using same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a rubber composition having both low heat generation and high anti-fracture by mixing N,N'-m-xylene-bis-citraconimide and a hydrazide compound having a specific structure with a rubber component comprising natural rubber and/or isoprene rubber and a diene-based rubber as a residual component. SOLUTION: A composition of the present invention is obtained by mixing 0.1-1.5 pts.wt. of N,N'-m-xylene-bis-citraconimide and 0.1-5 pts.wt. of at least one of compounds represented by formula I (A is an aromatic ring, hydantoin ring or the like; X is hydroxyl group, amino group or the like; and R3 and R4 are an 1-18C alkyl, a cycloalkyl and an aromatic ring) or formula II (R5 and R6 are an 1-18C alkyl group, a cycloalkyl group and an aryl group) with 100 pts.wt. of a rubber component comprising not less than 70 wt.% of natural rubber and/or isoprene rubber and a diene-based rubber as a residual component. 20-60 pts.wt. of carbon black and 1-20 pts.wt. of silica are mixed with 100 pts.wt. of the rubber component.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber compound having excellent low heat build-up and high resistance to breakage, and a pneumatic tire using the same, which is suitable for heavy loads.

[0002]

2. Description of the Related Art In general, truck and bus tires (TBs) are used.
R tire), there is a demand for a tread rubber having excellent wear resistance, low heat build-up, and breakage resistance. Normally, heavy-duty pneumatic tires generate a large amount of tread heat during running.Therefore, the tread rubber has a two-layer structure, and the outer layer cap rubber has excellent wear resistance and the inner layer base rubber has low heat build-up. There is a need for an improved rubber composition.

As means for improving the heat durability of a tire, there are a method using a large amount of a low heat-generating base rubber and a method using a lower heat-generating base rubber. Until now, if the volume of the base rubber was increased, the tear resistance of the base rubber, which is inconsistent with low heat generation, was insufficient.
The base rubber was torn, causing deterioration in appearance at the end of use.

[0004] As a countermeasure, the present applicant has previously used N, N'-m-xylenebis-citraconimide and silica to prevent heat sag and improve heat generation durability. A rubber composition in which tear resistance is improved by silica and a heavy-duty pneumatic tire using the same have been developed (JP-A-9-32857).
No. 4).

[0005] In recent years, pneumatic tires for heavy loads have been further flattened and reduced in diameter, and use conditions have become severe. For this reason, higher heat generation and tear resistance are required to be higher than before. The rubber composition described in the above publication and the pneumatic tire for heavy load using the same have improved tearing resistance while improving heat generation durability (low heat generation property). However, it is not sufficient for the requirement of low heat generation. Therefore,
There is a demand for a rubber composition having improved tear resistance while further improving low heat build-up, and a pneumatic tire using the rubber composition suitable for heavy loads.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a rubber compound having excellent low heat build-up and high fracture resistance. It is an object of the present invention to provide a pneumatic tire suitable for heavy loads.

[0007]

DISCLOSURE OF THE INVENTION The present inventors have studied various specific hydrazide compounds which are excellent as rubber exothermic improvers and the like, and clarified various requirements necessary for heavy load use. In addition to succeeding in obtaining a rubber composition of the above, and using this as a base rubber of pneumatic tires for heavy loads, etc., in order to have excellent tear resistance, it is necessary to use a larger amount of base rubber than before. Heat resistance (low heat generation) as a result,
The inventor succeeded in obtaining a pneumatic tire suitable for heavy load and the like having the above-mentioned purpose and excellent in durability, and completed the present invention. That is, the present invention resides in the following (1) to (5). (1) N-N'-m-xylene-bis-citraconimide is used in an amount of 0.1 to 100 parts by weight of a rubber component containing 70% by weight or more of natural rubber and / or isoprene rubber and the remainder being a diene rubber. 1.5 parts by weight, and 0.1 to 5 parts by weight of at least one selected from the group consisting of chemical substances represented by the following general formula (I) or (II). Rubber composition.

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Embedded image (2) The rubber composition according to the above (1), further comprising 20 to 60 parts by weight of carbon black and 1 to 20 parts by weight of silica based on 100 parts by weight of the rubber component. (3) The nitrogen adsorption surface area of the carbon black (N ₂ S
The rubber composition according to the above (2), wherein A) is at least 70 m ² / g. (4) The above-mentioned (1) as base rubber with cap / base structure
A pneumatic tire using the rubber composition according to any one of (1) to (3). (5) The pneumatic tire according to (4), wherein the cap / base volume ratio of the cap / base structure is 90/10 to 10/90.

[0008]

Embodiments of the present invention will be described below in detail. The rubber composition of the present invention contains natural rubber and / or
Alternatively, N-N 'is added to 100 parts by weight of a rubber component containing 70% by weight or more of isoprene rubber and the remainder being a diene rubber.
-M-xylene-bis-citraconimide 0.1 to
1.5 parts by weight and 0.1 to 5 parts by weight of at least one selected from the group consisting of hydrazide compounds represented by the following general formulas (I) and (II). It is assumed that.

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The rubber component used in the present invention is a natural rubber (N
R) and / or 70% by weight or more of isoprene rubber,
The remainder consists of diene rubber. In the present invention, an NR having a NR of 100% is desirable from the viewpoint of low heat build-up and breaking resistance, but any material containing 70% by weight or more of an isoprene rubber may be used. Therefore, butadiene rubber (BR), styrene-butadiene rubber (SB)
Up to 30% of a diene rubber such as R) can be blended. In the rubber component, if the NR and / or isoprene rubber is less than 70% by weight, the desired low heat build-up and fracture resistance cannot be exhibited, which is not preferable.

NN'-m-xylene- used in the present invention
Bis-citraconimide is represented by the following structural formula.

Embedded image This NN'-m-xylene-bis-citraconimide cures rubber, prevents sag, and improves low heat build-up.
The amount is 0.1 to 1.5 parts by weight, preferably 0.3 to 1.0 part by weight with respect to parts by weight. When the amount is less than 0.1 part by weight, the effects of the present invention cannot be achieved, and
Exceeding 2.0 parts by weight is not preferred because the puncture resistance is impaired.

The above-mentioned general formula (I) or (I)
The chemical substance represented by I) has a function of improving the tear resistance of the rubber while maintaining low heat build-up of the rubber composition. Of the chemical substances represented by the general formula (I), preferably, A in the general formula (I) is an aromatic ring, and X is a compound represented by the following formula:

Embedded image At least one selected from a hydroxy group and an amino group, wherein R _{1 to} R ₄ are hydrogen and a linear or branched alkyl group having 1 to 18 carbon atoms, a cycloalkyl group, an aromatic ring (each of which is the same); However, it may be at least one of the more selected chemical substances.

Specific chemical substances represented by the above general formula (I) include, for example, N ² , N ⁴ -di (1-methylethylidene) isophthalic dihydrazide, N ² , N ⁴ -di (1-methyl) propylidene) isophthalic acid dihydrazide, N ^2, N ⁴ - di (1,3-dimethyl-butylidene) isophthalic acid dihydrazide, N '- (1-methylethylidene) salicylic acid hydrazide, N' - (1-methylpropylidene) salicylic acid Hydrazide, N '-(1-methylbutylidene) salicylic acid hydrazide, N'-(1,3-dimethylbutylidene) salicylic acid hydrazide, N '-(2
-Furylmethylene) salicylic acid hydrazide and the like, and specific chemical substances represented by the general formula (II) include, for example, 1-hydroxy-N '-(1-methylethylidene) -2-naphthoic acid hydrazide , 1-hydroxy-N '-(1-methylpropylidene) -2-naphthoic acid hydrazide, 1-hydroxy-N'-(1-methylbutylidene) -2-naphthoic acid hydrazide, 1-hydroxy-N'- (1,3-dimethylbutylidene) -2-
Naphthoic acid hydrazide, 1-hydroxy-N '-(2-
Furylmethylene) -2-naphthoic acid hydrazide, 3-hydroxy-N '-(1-methylethylidene) -2-naphthoic acid hydrazide, 3-hydroxy-N'-(1-methylpropylidene) -2-naphthoic acid hydrazide , 3-hydroxy-N '-(1-methylbutylidene) -2-naphthoic acid hydrazide, 3-hydroxy-N'-(1,3-
Dimethylbutylidene) -2-naphthoic acid hydrazide, 3
-Hydroxy-N '-(2-furylmethylene) -2-naphthoic acid hydrazide, 3-hydroxy-N'-(1,2
-Diphenylethylidene) -2-naphthoic acid hydrazide and the like. The chemical substance represented by the general formula (I) or (II) is a starting material for 3-hydroxy-2-
It can be easily synthesized by heating and reacting naphthoic acid hydrazide and the like with acetone, methyl isobutyl ketone and the like.

The preferable chemical substances represented by the general formulas (I) and (II) are 3-hydroxy-N '-(1,1) in view of easiness of synthesis, cost and low heat generation effect.
3-dimethylbutylidene) -2-naphthoic acid hydrazide, 3-hydroxy-N '-(1,3-diphenylethylidene) -2-naphthoic acid hydrazide and 3-hydroxy-N'-(1-methylethylidene) -2 -Naphthoic acid hydrazide hydrazide, more preferably 3-hydroxy-N '-(1,3-diphenylethylidene)-
2-Naphthoic hydrazide is preferred.

The chemical substances represented by the above general formulas (I) and (II) can be used alone or in combination of two or more kinds.
It is used in the range of parts by weight, preferably 0.3 to 2.0.
Parts by weight. When the amount is in the range of 0.1 to 5 parts by weight, a rubber composition having both excellent low heat build-up and high fracture resistance can be obtained. When the compound is 0.
If the amount is less than 1 part by weight, the effects of the present invention cannot be achieved. If the amount exceeds 5 parts by weight, other performances are adversely affected, and it is not economical.

In the present invention, it is preferable to add carbon black as a reinforcing filler. Carbon black is used, is not particularly limited, preferably, nitrogen adsorption specific surface area (N ₂ SA) of 70m ² / g or more, more preferably, is desired to have a property of 80 to 120 ² / g . If the N ₂ SA is less than 70 m ² / g, the wear resistance deteriorates, which is not preferable. The compounding amount of the carbon black is 20 to 60 parts by weight, preferably 25 to 4 parts by weight, based on 100 parts by weight of the rubber component.
0 parts by weight. If the amount of carbon black is less than 20 parts by weight, the abrasion resistance is reduced, and if it is more than 60 parts by weight, the low heat build-up is unfavorably deteriorated.

In the present invention, silica may be further blended in addition to carbon black as the above-mentioned reinforcing filler.
The amount of the silica is 1.0 to 20 parts by weight, preferably 3 to 1 part by weight, per 100 parts by weight of the rubber component.
5 parts by weight. If the amount is less than 1 part by weight, the effects of the present invention cannot be achieved.
Low heat build-up deteriorates, which is not preferable.

When the above silica is used, it is preferable to use a silane coupling agent in combination. By using this silane coupling agent, the heat generation can be further reduced. As the silane coupling agent, for example, bis (3
-Triethoxysilylpropyl) polysulfide, γ-
Mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, 3-trimethoxysilylpropyl-N, N-dimethylcarbamoyltetrasulfide, 3-trimethoxysilylpropylbenzothiazolyltetrasulfide, 3-
Trimethoxysilylpropyl methacrylate monosulfide and the like. The amount of the silane coupling agent is preferably 1/20 to 1/5 with respect to the amount of silica.

In the present invention, in addition to the above, addition of vulcanizing agents, vulcanization accelerators, antioxidants, zinc white (ZnO), stearic acid, waxes, antioxidants and the like which are usually used in the rubber industry. An agent can also be compounded.

In the present invention, the rubber component having the above-mentioned compounding ratio, N-N'-m-xylene-bis-citraconimide, a chemical substance represented by the above formula (I) or (II),
Banbury mixer, such as carbon black and silica,
It is preferably used as a rubber composition for a pneumatic tire by kneading with a kneading machine such as a roll or an internal mixer, and the rubber composition is used as a base rubber having a cap / base structure by a conventional method. By
A pneumatic tire suitable for heavy loads and the like can be manufactured.

The cap / base volume ratio of the cap / base structure is preferably 90/10 to 10/90, more preferably 70/30 to 30/70. If the base is less than 10%, a low heat generation effect cannot be obtained.
If it exceeds 0%, the abrasion resistance of the tread portion decreases, which is not preferable.

[0021]

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples, but is not limited to the following Examples.

Examples 1 and 2 and Comparative Examples 1 to 4
A rubber composition was prepared using a Banbury mixer according to the formulation (parts by weight) shown in Table 1. Using each of the rubber compositions obtained above as a base rubber having a cap / base structure, a pneumatic tire for 11R225 14PR good road was produced by a conventional method, and the modulus (elastic modulus) and fracture were obtained by the following methods. Each property of elongation, destruction resistance, abrasion resistance, and low heat generation was evaluated. The volume ratio of the cap / base structure is 50/50. The tire performance was measured by measuring the above-prepared 11R225 14PR good road tire for 10 t.
It was evaluated after inserting it into a truck and running 100,000 km. The results are shown in Table 1 below.

[Evaluation of elastic modulus and elongation at break] Elastic modulus [M
₅₀ , M ₃₀₀ ], the elongation at break was cut out from the tire after running, a JIS # 3 sample was prepared, and the
It was evaluated on an Instron tensile tester according to SK6301. [Evaluation of Fracture Resistance] The state of the pattern blocks at both ends of the tread was observed, and the reciprocal of the number of missing blocks was calculated. The higher the value, the better the fracture resistance.

[Evaluation of Abrasion Resistance] The running distance when the cap rubber was completely worn (wear up to the wear indicator) was measured, and Comparative Example 2 was indicated as an index as a control (100). The higher the value, the better the wear resistance. [Evaluation of low heat generation] The heat generation temperature at the boundary between the belt and the tread rubber was measured, and Comparative Example 2 was controlled (10
0). The higher the numerical value, the better the low heat generation.

[0025]

[Table 1]

(Consideration of Table 1) As is evident from the results of Table 1 above, Examples 1 and 2 which fall within the scope of the present invention have a higher elastic modulus and fracture than Comparative Examples 1 to 4 which fall outside the scope of the present invention. Elongation,
It was found that it was excellent in fracture resistance, wear resistance and low heat generation. When viewed individually, when only the amount of N-N'-m-xylene-bis-citraconimide was increased from Comparative Example 2 in which silica and N-N'-m-xylene-bis-citraconimide were used in combination, low heat build-up was observed. It can be seen that, although improved, the fracture resistance is reduced. On the other hand, silica and NN'-m
In Example 1, in which -xylene-bis-citraconimide and 3-hydroxy-N '-(1,3-diphenylethylidene) -2-naphthoic acid hydrazide were applied, the resistance to destruction and heat generation were lower than those in Comparative Example 2. Have improved together,
It can be seen that Example 2 in which the amount of 3-hydroxy-N ′-(1,3-diphenylethylidene) -2-naphthoic acid hydrazide was increased further improved. However, N-N'-m
-Hydroxy-N '-(1,3-diphenylethylidene) -2 without using xylene-bis-citraconimide
Comparative Example 4 in which only -naphthoic acid hydrazide was added resulted in inferior low heat build-up, and according to Examples 1 and 2 within the scope of the present invention, 3-hydroxy-N '-(1,3-diphenylethylidene) It has been found that the combined use of -2-naphthoic acid hydrazide, silica and N-N'-m-xylene-bis-citraconimide makes it possible to achieve both high abrasion resistance and excellent low heat generation.

FIG. 1 shows strain (%) (horizontal axis) and stress (M
FIG. 6 is a characteristic diagram showing a relationship with Pa) [vertical axis]. The solid line indicates Example 2 and the dotted line indicates Comparative Example 2. In Example 2 in which BMH was added to Comparative Example 2, the rubber became harder in the low strain region, thereby improving the low heat buildup property. At the same time, the elongation at break (E _B ) was improved, so that the chipping resistance and It can be seen that the fracture resistance such as tear strength has been improved.

[0030]

According to the present invention, it is possible to provide a rubber compound having excellent low heat build-up and high fracture resistance, and a pneumatic tire using the rubber compound, which is suitable for heavy loads.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram (graph) showing a relationship between strain (%) [horizontal axis] and stress (MPa) [vertical axis].

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Claims (5)

[Claims] 1. A method in which natural rubber and / or isoprene rubber is
N-N'-m-xylene-bis- based on 100 parts by weight of a rubber component containing 0% by weight or more and the remainder being a diene rubber.
0.1 to 1.5 parts by weight of citraconic imide and 0.1 to 5 parts by weight of at least one selected from the group consisting of chemical substances represented by the following general formula (I) or (II) A rubber composition characterized by being compounded. Embedded image Embedded image 2. 100 parts by weight of the rubber component, 20 to 60 parts by weight of carbon black and 1 to 10 parts by weight of silica.
The rubber composition according to claim 1, which is blended with 20 parts by weight. 3. The rubber composition according to claim 2, wherein the carbon black has a nitrogen adsorption surface area (N ₂ SA) of 70 m ² / g or more. 4. A pneumatic tire using the rubber composition according to claim 1 as a base rubber having a cap / base structure. 5. The cap / cap of the base structure /
The pneumatic tire according to claim 4, wherein the volume ratio of the base is 90/10 to 10/90.