JP2005171016A - Rubber composition and radial tire using the same and used for heavy load - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition which simultaneously has good fatigue resistance, crack resistance, and initial physical property-holding characteristics. <P>SOLUTION: This rubber composition comprises 100 pts. wt. of a rubber component comprising 80 to 50 pts. wt. of natural rubber and/or polyisoprene rubber and 20 to 50 pts. wt. of polybutadiene rubber, 40 to 60 pts. wt. of carbon black having a nitrogen adsorption specific surface area of ≥90 m<SP>2</SP>/g, 0.3 to 1.8 pts. wt. of a compounding agent A represented by the formula: (C<SB>6</SB>H<SB>5</SB>-CH<SB>2</SB>)<SB>2</SB>N-(C=S)-(S)<SB>y</SB>-(CH<SB>2</SB>)<SB>x</SB>-(S)<SB>y</SB>-(C=S)-N(CH<SB>2</SB>-C<SB>6</SB>H<SB>5</SB>)<SB>2</SB>[(x) is 3 to 12; (y) is 1 to 8], and a vulcanization accelerator. The rubber composition satisfies the following relation:(a)/(b)=0.35 to 0.55, wherein (a) is the amount of the compounding agent A; (b) is the amount of the vulcanization accelerator, per 100 pts. wt. of the rubber component. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a rubber composition, and particularly to a rubber composition used in a chafer portion of a radial tire for heavy loads. The present invention also relates to a heavy duty radial tire, particularly an aircraft radial tire, characterized in that the rubber composition described above is used in a chafer portion.

  Since the number of carcass plies can be reduced as a feature of heavy duty radial tires, especially aircraft radial tires, it is possible to reduce the weight around the bead, but in response to this, deformation becomes larger than the bias tire, and the bead As a result, problems such as crack (torque crack) deformation and generation of rubber sticking due to setting tend to occur in the chafer (= rim cushion) portion.

  Increasing the hardness of the rubber is effective in improving the settling resistance of the rubber. However, if the hardness of the rubber is increased in this way, the crack resistance is deteriorated. That is, there is a trade-off between anti-sag and crack resistance.

  On the other hand, since these tires are often used multiple times by retreading, maintaining performance in use over a long period of time (as a base tire) is also an important consideration.

  As a countermeasure for the above-mentioned problem, for example, in Japanese Patent Application Laid-Open No. 7-172118, the failure of the bead portion due to rim rubbing is reduced by defining the physical properties (100% modulus) of the side rubber / stiffener rubber / chafer rubber. Japanese Patent Laid-Open No. 14-293113 proposes a method for suppressing the settling of the heel portion by defining the physical properties (100% modulus) of the heel rubber and the carcass gauge. In this method, too, it is insufficient to improve both cracks and sag in the bead portion and chafer portion of a heavy-duty radial tire used under severe conditions, particularly an aircraft radial tire. There is no mention of maintaining the performance.

  As described above, in this technical field, there is a continuous demand for a rubber composition having both good set resistance, crack resistance, and initial property retention.

  Prior art document information related to the invention of this application includes the following.

JP-A-7-172118 JP-A-14-293113 JP 2001-2833 A

  An object of the present invention is to provide a rubber composition having both good settling resistance, crack resistance, and initial property retention. Another object of the present invention is for heavy loads that have good sag resistance and crack resistance and can maintain initial performance over a long period of time by using the rubber composition in the chafer part. It is to provide a radial tire, in particular an aircraft radial tire.

The above purpose is
For 100 parts by weight of a rubber component comprising 80 to 50 parts by weight of natural rubber and / or polyisoprene rubber and 20 to 50 parts by weight of polybutadiene rubber,
40 to 60 parts by weight of carbon black having a nitrogen adsorption specific surface area of 90 m ² / g or more,
The following formula
(C ₆ H ₅ -CH ₂ ) ₂ N- (C = S)-(S) _y- (CH ₂ ) _x- (S) _y- (C = S) -N (CH ₂ -C ₆ H ₅ ) ₂
0.3 to 1.8 parts by weight of compounding agent A represented by: and a vulcanization accelerator,
A rubber composition comprising:
In the above formula,
x is 3-12, and y is 1-8,
The blending amount (a) of the compounding agent A and the blending amount (b) of the vulcanization accelerator with respect to 100 parts by weight of the rubber component are as follows:
a / b = 0.35 to 0.55
A rubber composition characterized by satisfying
This is achieved by the present invention including:

  According to the present invention, it is possible to provide a rubber composition having both good settling resistance, crack resistance, and initial property retention. Further, by using the rubber composition according to the present invention in the chafer part, a heavy-duty radial tire that has good sag resistance and crack resistance and can maintain initial performance over a long period of time, In particular, an aircraft radial tire can be provided.

  The present invention has a good sag resistance by blending a specific carbon black, a compounding agent having a specific structure, and a vulcanization accelerator in a specific compounding amount with respect to a rubber component having a specific composition. This is based on the finding that it is possible to provide a rubber composition having both crack resistance and initial property retention.

That is, the rubber composition according to the present invention is
For 100 parts by weight of a rubber component comprising 80 to 50 parts by weight of natural rubber and / or polyisoprene rubber and 20 to 50 parts by weight of polybutadiene rubber,
40 to 60 parts by weight of carbon black having a nitrogen adsorption specific surface area of 90 m ² / g or more,
The following formula
(C ₆ H ₅ -CH ₂ ) ₂ N- (C = S)-(S) _y- (CH ₂ ) _x- (S) _y- (C = S) -N (CH ₂ -C ₆ H ₅ ) ₂
0.3 to 1.8 parts by weight of compounding agent A represented by: and a vulcanization accelerator,
A rubber composition comprising:
In the above formula,
x is 3-12, and y is 1-8,
The blending amount (a) of the compounding agent A and the blending amount (b) of the vulcanization accelerator with respect to 100 parts by weight of the rubber component are as follows:
a / b = 0.35 to 0.55
Is a rubber composition characterized by satisfying

  In the rubber composition according to the present invention, the polybutadiene rubber (BR) occupies 20 to 50 parts by weight, preferably 25 to 45 parts by weight, out of 100 parts by weight of the rubber component, and the balance is natural rubber (NR) and / or. Polyisoprene rubber (IR) is preferably occupied. When the blending amount of the polybutadiene rubber (BR) is less than 20 parts by weight with respect to 100 parts by weight of the rubber component, the crack resistance is deteriorated and cracks (torque cracks) at the contact portion with the rim are likely to occur. Therefore, it is not preferable. On the other hand, when the blending amount of polybutadiene rubber (BR) exceeds 50 parts by weight with respect to 100 parts by weight of the rubber component, it is not preferable because the settling resistance deteriorates and the rubber tends to sag.

The carbon black to be blended in the rubber composition according to the present invention desirably has a nitrogen adsorption specific surface area (N ₂ SA) of 90 m ² / g or more, preferably 110 m ² / g or more. When the nitrogen adsorption specific surface area (N ₂ SA) is less than 90 m ² / g, the crack resistance of the rubber composition after vulcanization becomes insufficient, which is not preferable. In the description of the present specification, “nitrogen adsorption specific surface area (N ₂ SA)” means a specific surface area [m ² / g] measured according to JIS K6217.

  In the rubber composition according to the present invention, the compounding amount of the carbon black is 40 to 60 parts by weight, preferably 45 to 55 parts by weight with respect to 100 parts by weight of the rubber component. When the blending amount of the carbon black is less than 40 parts by weight with respect to 100 parts by weight of the rubber component, the hardness in the rubber composition after vulcanization becomes insufficient. On the contrary, when the blending amount of the carbon black exceeds 60 parts by weight with respect to 100 parts by weight of the rubber component, the heat build-up in the rubber composition after vulcanization is increased, which is not preferable.

As described above, x and y representing the lengths of the methylene chain and sulfur chain in the blend A blended in the rubber composition according to the present invention are 3 to 12 (preferably 4 to 10) and 1 to 1, respectively. 8 (preferably 2-6) is desirable. When x is less than 3, the initial breaking elongation is lowered, which is not preferable. On the contrary, when x exceeds 12, it is not preferable because exothermic property is deteriorated. Further, when y is less than 1 (that is, 0 (zero)), it does not function as a vulcanizing agent, which is not preferable. Conversely, when y exceeds 8, the effect of improving the heat aging resistance becomes insufficient, which is not preferable. Particularly preferred compounding agent A is one in which x is 6 and y is 2, that is,
(C ₆ H ₅ -CH ₂ ) ₂ N- (C = S)-(S) _2- (CH ₂ ) _6- (S) _2- (C = S) -N (CH ₂ -C ₆ H ₅ ) ₂
Is mentioned.

  Furthermore, in the rubber composition according to the present invention, the compounding amount of the compounding agent A is 0.3 to 1.8 parts by weight, preferably 0.4 to 0.8 parts by weight with respect to 100 parts by weight of the rubber component. A part by weight is desirable. When the compounding amount of the compounding agent A is less than 0.3 parts by weight with respect to 100 parts by weight of the rubber component, the effect of improving the initial physical property retention in the rubber composition after vulcanization becomes insufficient, which is not preferable. . On the contrary, when the compounding amount of the compounding agent A exceeds 1.8 parts by weight with respect to 100 parts by weight of the rubber component, the initial breaking elongation in the rubber composition after vulcanization becomes insufficient, which is not preferable.

  The compounding agent A itself is a compound known in the rubber compounding technical field. For example, in Japanese Patent Application Laid-Open No. 2001-2833, a vulcanizable rubber composition comprising a diene rubber and a conventional additive is added to a rubber. 100 parts by weight of component a) 0.5 to 3.8 parts by weight of the compound corresponding to the above compounding agent A, b) 0.5 to 2 parts by weight of sulfur, and c) at least one vulcanization It is disclosed that by blending 0.5 to 3.0 parts by weight of the accelerator, the tear resistance and aging resistance are improved without deteriorating the heat build-up of the rubber composition after vulcanization. .

  However, in the present invention, as described above, the rubber component having a specific composition is blended with a specific carbon black, a compounding agent A, and a vulcanization accelerator in a specific compounding amount, thereby achieving good resistance. The present inventors have found that it is possible to provide a rubber composition having both sag, crack resistance, and initial physical property retention.

  As the vulcanization accelerator used in the rubber composition according to the present invention, any vulcanization accelerator generally used in the technical field may be used, but a preferable vulcanization accelerator is used. Examples of 2-mercaprobenzothiazole (MBT), dibenzothiazole disulfide (MBTS), N-cyclohexyl-2-benzothiazole sulfenamide (CBS), N-tert-butyl-2-benzothiazolyl-sulfur Fenamide (TBBS), N, N-dicyclohexyl-2-benzothiazolylsulfenamide (DCBS), diphenylguanidine (DPG), tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), and tetrakis (2 -Ethylhexyl) Ram disulfide (TOT-N) and the like. Among these, a particularly preferred vulcanization accelerator is N-tert-butyl-2-benzothiazolyl-sulfenamide (TBBS), for example, trade name “Noxeller NS-F” from Ouchi Shinsei Chemical Co., Ltd. Is commercially available.

  In the rubber composition according to the present invention, the ratio (a / b) of the blending amount (a) of the blending agent A to the blending amount (b) of the vulcanization accelerator is 100 parts by weight of the rubber component. It is desirable that it is 0.35 to 0.55, preferably 0.35 to 0.50. When the a / b is less than 0.35, the crack resistance and initial elongation at break in the rubber composition after vulcanization are insufficient, which is not preferable. On the contrary, when a / b is more than 0.55, the set resistance and the initial elongation at break in the rubber composition after vulcanization become insufficient.

  The rubber composition according to the present invention includes a process oil, a plasticizer, a softener, a vulcanization aid, a vulcanization retarder, a vulcanization activator, an anti-aging agent, and / or the like, and / or general in the rubber compounding technology Various other additives used in can be further blended. The blending amounts of these additives can be set to conventional general blending amounts as long as the object of the present invention is not violated.

  The rubber composition according to the present invention can be produced by mixing the above components using a known rubber kneading machine (for example, a roll, a Banbury mixer, a kneader, etc.).

  In a preferred embodiment of the present invention, by using the above rubber composition in the chafer portion, a radial for heavy load that has good sag resistance and crack resistance and can maintain initial performance over a long period of time. Tires are provided. The heavy duty radial tire according to a preferred embodiment of the present invention is particularly useful for use as an aircraft radial tire.

  Although the present invention will be described in more detail with reference to various comparative examples and examples described below, the technical scope of the present invention is not limited to these examples.

Comparative Examples 1-4 and Examples 1 and 2
Various compounding components used in the preparation of various test pieces to be described later are listed below.

Compounding natural rubber (NR): RSS No. 1 Polybutadiene rubber (BR): “Nipol BR1220” manufactured by Nippon Zeon Co., Ltd.
Carbon black (CB): “Show Black N220” manufactured by Showa Cabot Co., Ltd. (ISAF grade, N ₂ SA = 119 m ² / g)
Zinc Hana: “Zinc oxide 3 types” manufactured by Shodo Chemical Industry Co., Ltd.
Stearic acid: “Bead stearic acid” manufactured by NOF Corporation
Anti-aging agent (6PPD): “SANTOFLEX 6PPD” (N-phenyl-N′-1,3-dimethylbutyl-p-phenylenediamine) manufactured by FLEXSYS
Wax: “Sunnock” manufactured by Ouchi Shinsei Chemical Co., Ltd.

Sulfur: "Oil-treated sulfur" (5% oil-treated powder sulfur) manufactured by Hosoi Chemical Co., Ltd.
Formulation A: “Vulcren KA9188” manufactured by Bayer ((C ₆ H ₅ —CH ₂ ) ₂ N— (C═S) —S ₂ — (CH ₂ ) ₆ —S ₂ — (C═S) —N ( CH ₂ -C ₆ H ₅ ) ₂ ) (Blend = a part by weight / 100 parts by weight of rubber component)
Vulcanization accelerator (TBBS): “Noxeller NS-F” (N-tert-butyl-2-benzothiazolyl-sulfenamide) manufactured by Ouchi Shinsei Chemical Co., Ltd. (blending amount = b parts by weight / 100 parts by weight of rubber component) )

Sample Preparation (1) Preparation of Various Rubber Compositions All the above components except sulfur, compounding agent A, and vulcanization accelerator (TBBS) are sealed in 1.8 liters in the compounding amounts shown in Table I below. Placed in mold mixer, kneaded for 3-5 minutes, and master batch was released when 165 ± 5 ° C was reached. To this master batch, sulfur having the blending amounts shown in Table I below, blending agent A, and vulcanization accelerator (TBBS) were added and kneaded with an 8-inch open roll. Comparative Examples 1 to 4 and Examples Various rubber compositions for 1 and 2 were obtained.

（２）各種試験片の調製
上記各種ゴム組成物を、１５×１５×０．２cmの金型中で１５０℃において３０分間プレス加硫して、各種ゴム組成物についての加硫物性評価用試験片をそれぞれ調製した。

(2) Preparation of various test pieces The above-mentioned various rubber compositions were subjected to press vulcanization at 150 ° C. for 30 minutes in a 15 × 15 × 0.2 cm mold, and a test for evaluating vulcanized properties of various rubber compositions. Each piece was prepared.

Evaluation of samples (1) Measurement of vulcanized physical properties of various test pieces Various vulcanized physical properties of test pieces made of various rubber compositions obtained in Comparative Examples 1 to 4 and Examples 1 and 2 were tested as follows. Measured according to the method.

1) Elongation retention:
For each of the above-mentioned various test pieces that have not been aged and each of the above-mentioned various test pieces that have been aged by holding in a gear oven in air at 80 ° C. for 96 hours (all of which are dumbbell-shaped type 3). According to K6251 (former JIS K6301), the elongation at break (Eb-BL) after aging and the elongation at break after aging (Eb-AG) were measured, and after aging for the elongation at break (Eb-BL) at unaged The percentage elongation at break (Eb-AG) was determined as a percentage. The larger the elongation retention rate, the higher the initial property retention of the rubber composition after vulcanization.

2) Hardness increase:
About each of the above-mentioned various test pieces that have not been aged and the above-mentioned various test pieces that have been aged in the same manner as 1) above, the hardness at non-aging (Hs-BL) and the hardness after aging (in accordance with JIS K6253) Hs-AG) was measured, and the increase in hardness after aging (Hs-AG) from the hardness at unaged (Hs-BL) was determined. The smaller the hardness increase, the higher the initial physical property retention of the rubber composition after vulcanization.

3) Set resistance:
For each of the unaged test pieces, the compression set [%] after 25% compression for 72 hours at 100 ° C. is measured in accordance with JIS K6262, and the reciprocal of the measured value of Comparative Example 1 is taken as 100. Expressed in The larger the index, the smaller the set amount, and the higher the set resistance of the rubber composition after vulcanization.

4) Crack resistance:
The above-mentioned various test pieces that were not aged were bent according to JIS K6260 at a cycle of 300 rpm, and the length of the crack [mm] when the number of bendings reached 10,000 was measured. The reciprocal of the measured value was represented by an index of 100. The larger the index, the higher the crack resistance of the rubber composition after vulcanization.

(2) Evaluation of vulcanized physical properties of various test pieces The results of vulcanized physical properties measured in 1) to 4) above for all examples are shown in Table I above. As shown in Table I above, in all examples, the compounding amounts of the rubber component, carbon black, zinc white, stearic acid, anti-aging agent (6PPD), and wax in the rubber composition are the same.

  The test piece of Comparative Example 1 has a standard composition comprising 1.9 parts by weight of sulfur and 1.3 parts by weight of a vulcanization accelerator (TBBS) per 100 parts by weight of the rubber component. It is the test piece prepared from the rubber composition used as a standard. As described above, in the evaluation of vulcanized physical properties of various test pieces of Comparative Examples 2 to 4 and Examples 1 and 2 described below, the measurement results of the test piece of Comparative Example 1 are used as a reference.

  In the test piece of Comparative Example 2, the compounding amount of sulfur was reduced from 1.9 parts by weight to 1.6 parts by weight with respect to 100 parts by weight of the rubber component. It is the test piece prepared from the rubber composition for a comparison which has the same composition as the comparative example 1 except having mix | blended 0.4 weight part with respect to this. As shown in Table I above, the ratio (a / b) of the blending amount (a) of the blending agent A to 100 parts by weight of the rubber component to the blending amount (b) of the vulcanization accelerator is as follows. Not satisfying the default of the invention (below the lower limit), the hardness of unaged increased, the increase in hardness was suppressed, and the set resistance was improved, but the elongation retention and crack resistance deteriorated .

  The test piece of Comparative Example 3 has the same composition as Comparative Example 2 except that the amount of compounding agent A was increased from 0.4 parts by weight to 1.5 parts by weight with respect to 100 parts by weight of the rubber component. It is the test piece prepared from the rubber composition for a comparison. As shown in Table I above, a / b does not satisfy the default of the present invention (much higher than the upper limit), and compared with Comparative Example 1 serving as a reference, it is not aged. Although the hardness increased, the increase in hardness was suppressed, but the elongation retention rate, set resistance, and crack resistance were insufficient.

  Contrary to the above Comparative Example 3, the test piece of Comparative Example 4 except that the amount of compounding agent A was reduced from 0.4 parts by weight to 0.2 parts by weight with respect to 100 parts by weight of the rubber component, It is the test piece prepared from the rubber composition for a comparison which has the same composition as the comparative example 2. As shown in Table I above, a / b does not satisfy the default of the present invention (significantly below the lower limit), and the hardness is excluded as compared with Comparative Example 1 serving as a reference standard. Each physical property deteriorated slightly.

  On the other hand, in the test piece of Example 1, the amount of sulfur was reduced from 1.9 parts by weight to 1.4 parts by weight with respect to 100 parts by weight of the rubber component. Except for adding 0.7 parts by weight to parts by weight and further increasing the amount of vulcanization accelerator (TBBS) from 1.3 parts by weight to 1.4 parts by weight with respect to 100 parts by weight of the rubber component. 1 is a test piece prepared from a rubber composition according to the present invention having the same composition as Comparative Example 1. As shown in Table I above, a / b satisfies the default of the present invention, and simultaneously improves initial physical property retention (hardness and elongation retention), set resistance, and crack resistance. Succeeded in doing. However, there was room for improvement with respect to elongation at break due to unaging.

  Next, the test piece of Example 2 reduced the compounding amount of the vulcanization accelerator (TBBS) from 1.4 parts by weight to 1.3 parts by weight with respect to 100 parts by weight of the rubber component, and at the same time, Test prepared from the rubber composition according to the present invention having the same composition as in Example 1 except that the blending amount was reduced from 0.7 parts by weight to 0.5 parts by weight with respect to 100 parts by weight of the rubber component. It is a piece. As shown in the above-mentioned Table I, a / b also satisfies the default of the present invention in this example, and the initial physical property retention (hardness and elongation retention) achieved in Example 1 was achieved. In addition, the present inventors succeeded in improving the elongation at break at the same time without impairing the effect of improving the set resistance and crack resistance.

  From the above results, in accordance with the provisions of the present invention, a specific carbon black, a compounding agent having a specific structure, and a vulcanization accelerator are compounded in a specific compounding amount with respect to a rubber component having a specific composition. The rubber composition after vulcanization was found to be able to simultaneously achieve good set resistance, crack resistance, and initial physical property retention. Such a rubber composition is used in a heavy duty radial tire that is required to have good sag resistance and crack resistance and to maintain initial performance for a long period of time, particularly in a chafer portion of a radial tire for aircraft. It is suitable for.

Claims (4)

For 100 parts by weight of a rubber component comprising 80 to 50 parts by weight of natural rubber and / or polyisoprene rubber and 20 to 50 parts by weight of polybutadiene rubber,
40 to 60 parts by weight of carbon black having a nitrogen adsorption specific surface area of 90 m ² / g or more,
The following formula
(C ₆ H ₅ -CH ₂ ) ₂ N- (C = S)-(S) _y- (CH ₂ ) _x- (S) _y- (C = S) -N (CH ₂ -C ₆ H ₅ ) ₂
0.3 to 1.8 parts by weight of compounding agent A represented by: and a vulcanization accelerator,
A rubber composition comprising:
In the above formula,
x is 3-12, and y is 1-8,
The blending amount (a) of the compounding agent A and the blending amount (b) of the vulcanization accelerator with respect to 100 parts by weight of the rubber component are as follows:
a / b = 0.35 to 0.55
A rubber composition characterized by satisfying The compounding agent A is
(C ₆ H ₅ -CH ₂ ) ₂ N- (C = S)-(S) _2- (CH ₂ ) _6- (S) _2- (C = S) -N (CH ₂ -C ₆ H ₅ ) ₂
The rubber composition according to claim 1, wherein   A radial tire for heavy loads, wherein the rubber composition according to claim 1 or 2 is used in a chafer part.   A radial tire for aircraft, wherein the rubber composition according to claim 1 or 2 is used in a chafer part.