JP2005171015A - Rubber composition for coating steel cord - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for steel cord which has been improved in characteristics after aging while maintaining or improving the adhesion between the steel cord and a rubber. <P>SOLUTION: In the rubber composition for coating steel cord 0.05 to 0.4 pts.weight of an organic acid cobalt salt as a cobalt content, 3 to 7 pts.weight of sulfur, and 1 to 8 pts.weight of alkylphenol disulfide are blended to 100 pts.weight of a diene-based rubber. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a rubber composition for coating a steel cord, and more particularly, to a rubber composition for coating a steel cord that has improved physical properties after aging while maintaining or improving the adhesion performance between the steel cord and rubber.

  Important required properties of steel cord coating rubber compositions used in tires for passenger cars, buses, trucks, etc. include high adhesion, high rigidity, and high durability. Are in a reciprocal relationship. Conventionally, this balance has been achieved by making full use of the amount of cobalt in the organic cobalt salt, the amount of sulfur, the selection and the amount of RF resin (Japanese Patent Laid-Open Nos. 5-104678 and 10- 10). 81107, JP-A-10-297209, JP-A-2001-49044 and JP-A-2001-240701). However, since strain and stress concentrate on the bonded end of the steel cord and rubber, further improvement in the physical properties of the steel cord coating rubber composition is required to further improve tire durability. Yes.

JP-A-5-104678 JP-A-10-81107 Japanese Patent Laid-Open No. 10-297209 JP 2001-49044 A JP 2001-240701 A

  An object of the present invention is to provide a rubber composition for coating a steel cord, in particular, further improving the physical properties after aging while maintaining or improving the adhesion performance between the steel cord and rubber.

  According to the present invention, 0.05 to 0.4 parts by weight of organic acid cobalt as a cobalt amount, 3 to 7 parts by weight of sulfur, and 1 to 8 parts by weight of alkylphenol disulfide are added to 100 parts by weight of diene rubber. A rubber composition for coating a steel cord is provided.

  In the present invention, as a result of examining the improvement of physical properties while maintaining or improving the adhesion performance between steel cord and rubber in the rubber composition for coating steel cord, a certain amount of sulfur / cobalt was blended, and further, alkylphenol It has been found that by using disulfide in combination, it is possible to improve various physical properties with good durability.

  That is, the steel cord covering rubber composition according to the present invention has 0.05 to 0.4 parts by weight of organic acid cobalt as a cobalt amount, 3 to 7 parts by weight of sulfur, and 100 parts by weight of diene rubber. It is a rubber composition characterized by blending 1 to 8 parts by weight of alkylphenol disulfide.

  As the diene rubber component used in the rubber composition for coating a steel cord according to the present invention, natural rubber or diene synthetic rubber can be used alone or a mixed system thereof can be used. Examples of the diene-based synthetic rubber include various butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), polyisoprene rubber (IR), butyl rubber (IIR), acrylonitrile-butadiene copolymer rubber, and chloroprene rubber. , Ethylene-propylene-diene copolymer rubber, styrene-isoprene copolymer rubber, styrene-butadiene copolymer rubber, and the like.

  Examples of the organic acid cobalt used in the rubber composition for coating a steel cord according to the present invention include, for example, cobalt naphthenate, cobalt stearate, cobalt oleate, cobalt linoleate, cobalt linolenate, cobalt palmitate, and cobalt neodecanoate. , Cobalt rosinate, cobalt tall oil, cobalt trineodecanoate and the like. In the present invention, the organic acid cobalt is blended in an amount of 0.05 to 0.4 parts by weight, more preferably 0.1 to 0.3 parts by weight, based on 100 parts by weight of the diene rubber. The If the amount of cobalt is less than 0.05 parts by weight, the expected effect of increasing the modulus cannot be exhibited. Conversely, if the amount exceeds 0.4 parts by weight, the processability deteriorates and the physical properties of the vulcanized rubber are remarkably reduced. Therefore, it is not preferable.

  Sulfur used in the rubber composition for coating a steel cord according to the present invention is blended in an amount of 3 to 7 parts by weight, more preferably 3 to 5 parts by weight. When the amount of sulfur exceeds 7 parts by weight, the physical properties are deteriorated and the adhesiveness after aging is also inferior. On the other hand, if the sulfur content is less than 3 parts by weight, the adhesiveness is deteriorated.

  Examples of the alkylphenol disulfide used in the steel cord coating rubber composition according to the present invention include poly (amylphenol disulfide) and the like, and are blended in an amount of 1 to 8 parts by weight. If the blending amount of the alkylphenol disulfide is less than 1 part by weight, the adhesiveness of the rubber composition is inferior, and conversely if the blending amount exceeds 8 parts by weight, the physical properties of the rubber are lowered. .

  The rubber composition for coating a steel cord of the present invention further includes a vulcanization or crosslinking agent, a vulcanization or crosslinking accelerator, a reinforcing agent such as carbon black, various oils, an anti-aging agent, a filler, a softener, and a plasticizer. Various compounding agents and additives generally blended for tires, etc. can be blended, and the blending amounts of these blending agents and additives may be general amounts as long as they do not contradict the purpose of the present invention. it can.

  Hereinafter, the present invention will be further described with reference to standard examples, examples, and comparative examples, but it goes without saying that the scope of the present invention is not limited to these examples.

Preparation of test samples Master batches released when the components shown in Table 1 below, excluding sulfur and vulcanization accelerator, were kneaded for 3 to 5 minutes in a 1.8 L closed mixer and reached a temperature of 150 ± 5 ° C. Sulfur and a vulcanization accelerator were added to and kneaded with an 8-inch open roll to obtain a rubber composition. A part of this composition was subjected to an adhesion test after aging. Next, the remaining rubber composition was press vulcanized in a 15 cm × 15 cm × 0.2 cm mold at 148 ° C. for 45 minutes to prepare a test piece (rubber sheet), which was subjected to a JIS hardness test, before aging. And subjected to a tensile test after aging and an adhesion test after aging.

Test Method 1) JIS Hardness (Hs): JIS A hardness was measured according to JIS K6253. A standard example was taken as 100 and evaluated by an index. The higher the index, the higher the hardness.
2) Tensile properties: The elongation at break was measured according to JIS 6251. A standard example was taken as 100 and evaluated by an index. The larger the index, the better.
3) Tensile properties after aging: Elongation at break after standing in a gear oven at 90 ° C. for 48 hours was measured according to JIS K6251. A standard example was taken as 100 and evaluated by an index. The larger the index, the better.
4) Adhesiveness after aging: Adhesiveness after leaving a rubber composition in contact with a brass-plated steel cord and vulcanizing the test piece for 48 hours in an oven at 90 ° C , Measured according to the pull-out test method of ASTM D2229. A standard example was taken as 100 and evaluated by an index. The larger the index, the better.

Standard example, Examples 1-5 and Comparative Examples 1-6
The results are shown in the table below.

  From the above, it can be seen that the steel cord coating rubber composition according to the present invention has improved physical properties before aging and after aging and adhesion after aging.

  From the above results, if a rubber layer made of a rubber composition for coating a steel cord according to the present invention is disposed on a carcass and / or a belt as a rubber for coating a steel cord of a tire, for example, a pneumatic tire having extremely excellent durability Can be obtained.

Claims (2)

  Steel cord coating rubber containing 0.05 to 0.4 parts by weight of organic acid cobalt as cobalt, 100 parts by weight of diene rubber, 3 to 7 parts by weight of sulfur and 1 to 8 parts by weight of alkylphenol disulfide Composition. The rubber composition for coating a steel cord according to claim 1, wherein the organic acid cobalt is blended in an amount of 0.1 to 0.3 parts by weight and 3 to 5 parts by weight of sulfur.