JP2015034196A - Rubber composition for tire tread - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition in which low heat generation performance of a vulcanized rubber can be improved while processability of the rubber composition is improved, and to provide a pneumatic tire having a tire tread having low heat generation performance and excellent high mileage performance.SOLUTION: A rubber composition for a tire tread is prepared by blending 20 to 60 parts by mass of carbon black, 0.05 to 5.0 parts by mass of a dihydrazide compound, and 0.1 to 2.0 parts by mass of an inorganic acid metal salt in 100 parts by mass of a diene rubber. Thereby, low heat generation performance of a vulcanized rubber is improved while preventing prevulcanization (scorching) of the rubber composition and improving processability.

Description

  The present invention relates to a rubber composition for a tire tread, and the rubber composition for a tire tread is useful as a raw material for a vulcanized rubber excellent in low heat generation performance.

  In recent years, from the viewpoint of energy saving, the tire industry has been actively developing low fuel consumption tires. For the development of low fuel consumption tires, especially the low heat generation performance of the rubber part of the tire tread obtained by vulcanization. It is said that improvement is essential.

  As a technique for improving the low heat generation performance of a vulcanized rubber, Patent Document 1 described below describes a technique for blending a hydrazide compound and a reinforcing filler with a rubber composition as a raw material.

Japanese Patent Publication No. 7-57828

  However, as a result of intensive studies by the present inventors, it has been found that the above prior art has the following problems. Specifically, with the technique described in Patent Document 1, the processability of the rubber composition tends to deteriorate, and the improvement in the low heat generation performance of the vulcanized rubber is insufficient.

  When a dihydrazide compound is blended in the rubber composition, the low heat generation performance of the resulting vulcanized rubber is improved. On the other hand, when a dihydrazide compound is blended in the rubber composition, the scorch time of the rubber composition tends to be shortened, and as a result, the point that processability deteriorates has been a big problem.

  This invention is made | formed in view of the said situation, The objective is to provide the rubber composition which can improve the low heat generation performance of vulcanized rubber, improving the processability of a rubber composition. The present invention also relates to a pneumatic tire provided with a tire tread having low heat generation performance and excellent fuel economy performance.

  In order to solve the above problems, the present invention comprises the following arrangement. That is, this invention contains carbon black 20-60 mass parts, dihydrazide compound 0.05-5.0 mass parts, and inorganic acid metal salt 0.1-2.0 mass parts with respect to 100 mass parts of diene rubber. The present invention relates to a rubber composition for tire treads.

  Since the rubber composition according to the present invention contains a dihydrazide compound, the dispersibility of carbon black in the rubber composition is improved. Therefore, even the final vulcanized rubber improves the dispersibility of carbon black, and as a result, the low heat generation performance of the vulcanized rubber improves. On the other hand, when the dihydrazide compound is added alone to the rubber composition, early vulcanization (scorch) of the rubber composition is likely to occur, and the processability is often adversely affected. However, in the present invention, since the inorganic acid metal salt is contained in the rubber composition in addition to the dihydrazide compound, undesired shortening of the scorch time can be prevented. The reason why such an effect is obtained is not clear, but the rubber composition containing the dihydrazide compound exhibits basicity. However, when an inorganic acid metal salt is present in the rubber composition, the dihydrazide compound and the polymer and / or carbon black are used. It is possible to effectively neutralize the rubber composition without causing reaction inhibition with.

  In the present invention, the blending amount of carbon black with respect to 100 parts by weight of the diene rubber is 20 to 60 parts by weight, the blending amount of the dihydrazide compound is 0.05 to 5.0 parts by weight, and the blending amount of the inorganic acid metal salt. 0.1 to 2.0 parts by mass. By setting the blending amount of the three components of carbon black, dihydrazide compound, and inorganic acid metal salt to such a ratio, in the present invention, the low exothermic improvement effect of the vulcanized rubber and the processability improvement effect of the rubber composition Can be balanced in a balanced manner.

  Furthermore, the present invention relates to a pneumatic tire obtained using the rubber composition for a tire tread described above. A pneumatic tire provided with a tire tread obtained using the rubber composition for a tire tread as a raw material has low heat generation performance, so that fuel efficiency performance is extremely improved.

  The rubber composition for a tire tread according to the present invention includes 20 to 60 parts by mass of carbon black, 0.05 to 5.0 parts by mass of a dihydrazide compound, and 0.1 to 0.1 parts of an inorganic acid metal salt with respect to 100 parts by mass of the diene rubber. Contains 2.0 parts by weight.

  Examples of the diene rubber include natural rubber (NR), polyisoprene rubber (IR), polystyrene butadiene rubber (SBR), polybutadiene rubber (BR), chloroprene rubber (CR), and nitrile rubber (NBR). If necessary, a terminal-modified one (for example, terminal-modified BR, terminal-modified SBR, etc.) or a substance modified to give a desired property (for example, a modified NR) can be suitably used. Regarding polybutadiene rubber (BR), in addition to those synthesized using a cobalt (Co) catalyst, a neodymium (Nd) catalyst, a nickel (Ni) catalyst, a titanium (Ti) catalyst, and a lithium (Li) catalyst, WO2007 What was synthesize | combined using the polymerization catalyst composition containing the metallocene complex as described in -129670 can also be used.

  When considering the low heat generation performance of the vulcanized rubber, the polystyrene butadiene rubber has a styrene content of 10 to 40% by mass, a vinyl bond content of the butadiene part of 10 to 70% by mass, and a cis content of 10% by mass or more. Particularly preferred are those having a styrene content of 15 to 25% by mass, a vinyl bond content of the butadiene part of 10 to 60% by mass, and a cis content of 20% by mass or more. Moreover, when using as a tread rubber part of a pneumatic tire, it is preferable to use a non-oiled type polystyrene butadiene rubber rather than an oiled type.

  In the present invention, natural rubber (NR) can be suitably used as the diene rubber. When the total amount of the diene rubber is 100 parts by mass, it is preferable to contain 50 parts by mass or more of natural rubber, and 75 parts by mass. More preferably, it is more preferably about 100 parts by mass or more.

A dihydrazide compound is a compound having _two hydrazide groups (—CONHNH ₂ ) in the molecule. , 11-octadecadien-1,18-dicarbohydrazide and the like. Among these, in the present invention, use of isophthalic acid dihydrazide and adipic acid dihydrazide is preferable, and use of isophthalic acid dihydrazide is more preferable.

  The rubber composition for a tire tread according to the present invention contains 0.05 to 5.0 parts by mass of the dihydrazide compound with respect to 100 parts by mass of the diene rubber. As for the compounding quantity of a dihydrazide compound, it is more preferable that it is 0.1-3.0 mass parts.

  As the carbon black, for example, conductive carbon black such as acetylene black and ketjen black can be used in addition to carbon black used in normal rubber industry such as SAF, ISAF, HAF, FEF, and GPF.

  The tire tread rubber composition according to the present invention contains 20 to 60 parts by mass of carbon black per 100 parts by mass of the diene rubber. The blending amount of carbon black is more preferably 30 to 50 parts by mass.

  The inorganic acid metal salt is a metal salt of an inorganic acid such as hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid, boric acid, and the metal content includes sodium, potassium, lithium, rubidium, cesium, calcium, magnesium, strontium, copper , Aluminum, and antimony. In the present invention, in particular, sodium hydrogen sulfate containing sulfuric acid as an inorganic acid and sodium as a metal component can be suitably used.

  The tire tread rubber composition according to the present invention contains 0.1 to 2.0 parts by mass of an inorganic acid metal salt with respect to 100 parts by mass of the diene rubber. The compounding amount of the inorganic acid metal salt is more preferably 0.3 to 1.6 parts by mass.

  The rubber composition for a tire tread according to the present invention includes a diene rubber, carbon black, a dihydrazide compound, and an inorganic acid metal salt, a vulcanizing compound, carbon black, silica, a silane coupling agent, and an antioxidant. Zinc oxide, stearic acid, wax, softeners such as oil, processing aids, organic acid metal salts, and methylene acceptors and methylene donors can be blended.

  Examples of organic acid metal salts include cobalt naphthenate, cobalt stearate, cobalt borate, cobalt oleate, cobalt maleate, and cobalt trineodecanoate.

  As the methylene acceptor, a phenolic compound or a phenolic resin obtained by condensing a phenolic compound with formaldehyde is used. Such phenolic compounds include phenol, resorcin or alkyl derivatives thereof. Alkyl derivatives include methyl group derivatives such as cresol and xylenol, and derivatives with long chain alkyl groups such as nonylphenol and octylphenol. The phenol compound may contain an acyl group such as an acetyl group as a substituent.

  In addition, phenolic resins obtained by condensing phenolic compounds with formaldehyde include resorcin-formaldehyde resins, phenolic resins (phenol-formaldehyde resins), cresol resins (cresol-formaldehyde resins), and formaldehyde composed of a plurality of phenolic compounds. Resin etc. are included. These are uncured resins that have liquid or heat fluidity.

  Among these, from the viewpoint of compatibility with the rubber component and other components, the density of the resin after curing, and the reliability, the methylene acceptor is preferably resorcin or a resorcin derivative, and in particular, resorcin or resorcin Alkylphenol-formalin resins are preferred.

  As the methylene donor, hexamethylenetetramine or melamine resin is used. As such a melamine resin, for example, methylol melamine, a partially etherified product of methylol melamine, a condensate of melamine, formaldehyde, and methanol is used, and among them, hexamethoxymethyl melamine is particularly preferable.

  As the additional rubber, the diene rubber can be used similarly.

  As an anti-aging agent, an aromatic amine-based anti-aging agent, an amine-ketone anti-aging agent, a monophenol anti-aging agent, a bisphenol anti-aging agent, a polyphenol anti-aging agent, dithiocarbamic acid, which are usually used for rubber Anti-aging agents such as a salt-based anti-aging agent and a thiourea-based anti-aging agent may be used alone or in an appropriate mixture. The content of the anti-aging agent is more preferably 0 to 5.0 parts by mass and further preferably 0.5 to 3.0 parts by mass with respect to 100 parts by mass of the rubber component.

  Examples of the vulcanizing compounding agent include vulcanizing agents such as sulfur and organic peroxides, vulcanization accelerators, vulcanization acceleration aids, vulcanization retarders and the like.

  Sulfur as the vulcanizing compounding agent may be normal sulfur for rubber. For example, powdered sulfur, precipitated sulfur, insoluble sulfur, highly dispersible sulfur and the like can be used. When the rubber physical properties and durability after vulcanization are taken into consideration, the sulfur content relative to 100 parts by mass of the rubber component is preferably 0.5 to 5.0 parts by mass in terms of sulfur content.

  As the vulcanization accelerator, sulfenamide vulcanization accelerator, thiuram vulcanization accelerator, thiazole vulcanization accelerator, thiourea vulcanization accelerator, guanidine vulcanization, which are usually used for rubber vulcanization. Vulcanization accelerators such as accelerators and dithiocarbamate vulcanization accelerators may be used alone or in admixture as appropriate. As for the compounding quantity of the vulcanization accelerator with respect to 100 mass parts of rubber components, 0.1-5.0 mass parts is preferable.

  The tire tread rubber composition according to the present invention includes a diene rubber, carbon black, a dihydrazide compound, and an inorganic acid metal salt, if necessary, a sulfur vulcanizer, a vulcanization accelerator, silica, and a silane. Coupling agent, zinc oxide, stearic acid, vulcanization accelerator, vulcanization retarder, organic peroxide, anti-aging agent, softener such as wax and oil, processing aid, Banbury mixer, kneader, roll It can be obtained by kneading using a kneader used in a normal rubber industry.

  In addition, the blending method of each of the above components is not particularly limited, and blending components other than the vulcanizing compound such as the sulfur vulcanizing agent and the vulcanization accelerator are kneaded in advance to obtain a master batch, and the remaining components are added. Further, a method of further kneading, a method of adding and kneading each component in an arbitrary order, a method of adding all components simultaneously and kneading may be used.

  Hereinafter, examples and the like specifically showing the configuration and effects of the present invention will be described. The evaluation items in Examples and the like were evaluated based on the following evaluation conditions for rubber samples obtained by heating and vulcanizing each rubber composition at 150 ° C. for 30 minutes.

(1) tan δ (low heat generation performance)
Evaluation was performed based on a tan δ value measured at an initial strain of 10%, a dynamic strain of 2%, a frequency of 50 Hz, and a temperature of 60 ° C. using a Toyo Seiki viscoelastic spectrometer. Evaluation means index evaluation with the value of Comparative Example 1 being 100, and the smaller the value, the better the low heat generation performance.

(2) Workability In accordance with JIS K6300-1, index evaluation was performed with the value of the scorch time t5 of Comparative Example 1 being 100. If the value is too short, it means that the storage stability before vulcanization is inferior, rubber burn is likely to occur during vulcanization, and the processability is poor. On the other hand, if the numerical value is too high, the progress of vulcanization is too slow, which means that the workability is poor. Therefore, when the value of t5 of Comparative Example 1 is 100, an index evaluation of 90 to 110 means excellent workability.

(Preparation of rubber composition)
In accordance with the formulation of Table 1, the rubber compositions of Examples 1 to 5 and Comparative Examples 1 to 5 were compounded and kneaded using a normal Banbury mixer to prepare a rubber composition. Each compounding agent described in Table 1 is shown below (in Table 1, the compounding amount of each compounding agent is shown in terms of parts by mass with respect to 100 parts by mass of the rubber component).
a) Diene rubber Natural rubber (NR) "RSS # 3"
b) Carbon Black (ISAF) “Seast 6”, manufactured by Tokai Carbon Co., Ltd. c) Process Oil manufactured by JOMO d) Anti-aging agent “6PPD”, manufactured by Ouchi Shinsei Chemical Co., Ltd. e) Zinc Hana “Zinc Hana 1”, Mitsui F) Stearic acid “Bead stearic acid” manufactured by Metal Mining Co., Ltd. g) Sodium hydrogen sulfate “Sodium hydrogen sulfate (acidic sodium sulfate)”, Nacalai Tesque “h” Dihydrazide compound “Isophthalic acid dihydrazide (IDH)” I) Sulfur “Powder Sulfur” manufactured by Nippon Finechem Co., Ltd. j) Vulcanization accelerator “Sunseller CM-G” manufactured by Sanshin Chemical Industry Co., Ltd.

  From the results in Table 1, it can be seen that the rubber compositions according to Examples 1 to 5 are excellent in processability and also excellent in low heat generation performance of the vulcanized rubber. On the other hand, since the rubber composition according to Comparative Example 2 contains only the dihydrazide compound, the processability of the rubber composition deteriorated. Moreover, since the rubber composition which concerns on the comparative example 3 has little content of an inorganic acid metal salt, workability deteriorated similarly. Furthermore, since the rubber composition according to Comparative Example 4 has a high content of the inorganic acid metal salt, the processability deteriorates, and the rubber composition according to Comparative Example 5 also has a high content of the dihydrazide compound. Sex deteriorated.

Claims (2)

  Carbon black 20-60 mass parts, dihydrazide compound 0.05-5.0 mass parts, and inorganic acid metal salt 0.1-2.0 mass parts are contained with respect to 100 mass parts of diene rubbers. Rubber composition for tire tread.   A pneumatic tire obtained using the rubber composition for a tire tread according to claim 1.