JP2010163544A - Rubber composition for tire tread, and pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for a tire tread capable of satisfying both abrasion resistance and a low fuel consuming property. <P>SOLUTION: This rubber composition for the tire tread contains 35 to 55 pts.wt. carbon black, having 105 to 165 mg/g iodine adsorption amount and 95 to 145 ml/100 g DBP absorbing amount, based on 100 pts.wt. rubber component, containing 60 to 90 pts.wt. natural rubber and/or isoprene rubber and 40 to 10 pts.wt. butadiene rubber synthesized by using a neodymium-based catalyst and having ≥96% cis-1,4 bond content and ≤0.6% vinyl group content, wherein its vulcanized material at 60°C has ≤0.100 loss tanδ. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a rubber composition for a tire tread used for a tread portion of a pneumatic tire, and a pneumatic tire using the same.

  In recent years, the demand for lower fuel consumption of automobiles has been increasing and tires are also required to have lower fuel consumption. As a part of a method for reducing the fuel consumption of a tire, there is a method of reducing hysteresis loss in a tread portion that contributes most to rolling resistance.

  In order to reduce the hysteresis loss of the tread portion, for example, carbon black or silica having a large particle size is used as a filler to be blended in the rubber composition, the blending amount of the carbon black is reduced, or a surfactant is blended. There is a way.

  However, although these methods can significantly reduce hysteresis loss and improve low heat buildup, there is a problem that wear resistance deteriorates.

  In addition, in Patent Document 1 below, in order to balance low fuel consumption and wear resistance, it is proposed to blend silica surface-treated with a silane coupling agent. The point of use is not disclosed.

  Patent Document 2 below proposes to use a butadiene rubber having a specific molecular weight distribution and a vinyl group content of 1% or less for a tread portion of a tire. However, this document does not disclose the use of a butadiene rubber having a cis-1,4 bond content and a vinyl group content specific to the present invention. This document is intended to improve the wear resistance without impairing the workability and fracture resistance, and does not disclose the loss tangent (tan δ) of the rubber composition. There is no suggestion of improving the exotherm.

  On the other hand, in Patent Document 3 below, a butadiene rubber synthesized using a neodymium catalyst as a diene rubber component has a cis-1,4 bond content of 95% or more and a vinyl group content of 1.8. % Or less of butadiene rubber 20-80 parts by weight and natural rubber and / or isoprene rubber 80-20 parts by weight are disclosed. However, this document, as a tread rubber composition for a studless tire, is a rubber composition for blending a rubber component with a plant granule, and is a rubber composition for the purpose of improving performance on ice and snow, and has a loss at a temperature of 60 ° C. Tangent (tan δ) is generally high and is not intended to improve low heat buildup.

  Patent Document 4 below discloses a butadiene rubber synthesized using a neodymium-based catalyst as a rubber component, having a cis-1,4 bond content of 95% or more and a vinyl group content of 1.8% or less. A rubber composition is disclosed in which a specific silica and carbon black are blended as a filler, and a tan δ of the vulcanizate is 0.05 to 0.1. However, this document relates to a rubber composition for a sidewall that requires bending fatigue resistance and cut resistance, and therefore, the required characteristics are different from the rubber composition for a tread that requires wear resistance. It does not suggest the present invention that achieves both wear resistance and low fuel consumption.

JP 2005-320371 A Japanese Patent Laid-Open No. 06-263920 JP 2005-344000 A JP 2006-124487 A

  The present invention has been made in view of the above points, and an object thereof is to provide a rubber composition for a tire tread that can achieve both wear resistance and low fuel consumption, and a pneumatic tire using the same. And

  The tire tread rubber composition according to the present invention is a butadiene rubber synthesized using 60 to 90 parts by weight of natural rubber and / or isoprene rubber and a neodymium catalyst, and has a cis-1,4 bond content of 96. % Of the butadiene rubber having a vinyl group content of 0.6% or less, and 100 parts by weight of the rubber component containing 100% by weight of the iodine component, the iodine adsorption amount is 105 to 165 mg / g, and the DBP absorption amount is 95. ˜145 ml / 100 g of carbon black is contained in 35 to 55 parts by weight, and the loss tangent tan δ of the vulcanizate measured at an initial strain of 15%, a dynamic strain of ± 2.5%, a frequency of 10 Hz and a temperature of 60 ° C. is 0. .100 or less.

  Moreover, the pneumatic tire according to the present invention is formed by producing a tread portion with the rubber composition for a tire tread.

  According to the present invention, in the rubber composition for a tire tread, the above-mentioned specific butadiene rubber is used in combination with natural rubber and / or isoprene rubber, and the specific carbon black is blended to maintain the wear resistance. The low heat build-up can be improved and the fuel consumption of the pneumatic tire can be reduced.

  Hereinafter, matters related to the implementation of the present invention will be described in detail.

  In the rubber composition of the present invention, the rubber component comprises a blend of 60 to 90 parts by weight of natural rubber and / or isoprene rubber and 40 to 10 parts by weight of a specific high cis-butadiene rubber. When the blending amount of the natural rubber and isoprene rubber exceeds 90 parts by weight, the wear resistance is inferior, and when the blending amount of the high cis-butadiene rubber exceeds 40 parts by weight, the processability is inferior and tan δ increases. The rubber component is basically composed of natural rubber and / or isoprene rubber and the specific high cis-butadiene rubber, but styrene butadiene rubber and neodymium catalyst as long as the effects of the present invention are not impaired. Other diene rubbers such as butadiene rubber polymerized by other methods may be included.

The specific high cis-butadiene rubber used in the rubber component is polymerized using a neodymium-based catalyst, has a cis-1,4 bond content of 96% or more, and has a vinyl group (1, (2-vinyl bond) It has a microstructure with a content of 0.6% or less. By using such a butadiene rubber, the tan δ of the vulcanized rubber can be lowered and the rolling resistance of the tire can be reduced as compared with the case of using a butadiene rubber polymerized with another catalyst such as a cobalt catalyst. can do. Here, examples of the neodymium-based catalyst include neodymium alone, a compound of neodymium and other metals, and an organic compound, and specific examples thereof include NdCl ₃ , Et-NdCl _{2, and the} like. The cis-1,4 bond content and vinyl group content are values measured using a nuclear magnetic resonance apparatus (NMR).

  Although it does not specifically limit as this high cis-butadiene rubber, It is preferable to use the high molecular weight butadiene rubber whose Mooney viscosity is 44 or more. The upper limit of Mooney viscosity is not particularly limited, but is preferably 70 or less. Here, the Mooney viscosity is the Mooney viscosity ML (1 + 4) at 100 ° C. measured according to JIS K6300.

  The rubber composition of the present invention has an iodine adsorption amount (IA) of 105 to 165 mg / g and a DBP (dibutyl phthalate) absorption amount of 95 to 145 ml / 100 g with respect to 100 parts by weight of the rubber component. A certain carbon black is mix | blended in 35-55 weight part. When the blending amount of the carbon black exceeds 55 parts by weight, the tan δ increases and the workability deteriorates although the wear resistance is excellent. On the contrary, if the amount of the carbon black is less than 35 parts by weight, the wear resistance is deteriorated. The blending amount of the carbon black is more preferably 35 to 50 parts by weight.

  The iodine adsorption amount of carbon black is a value measured according to JIS K6217, and the larger the value, the smaller the particle size is generally and the wear resistance is improved. When the iodine adsorption amount of carbon black is less than 105 mg / g, the wear resistance is poor. More preferably, the lower limit of iodine adsorption is 110 mg / g or more, the upper limit is 150 mg / g or less, and still more preferably 140 mg / g or less.

  The DBP absorption amount of carbon black is measured according to JIS K6217, and is an index of the structure of carbon black. By setting it within the above range, tan δ can be lowered while maintaining wear resistance. . If the DBP absorption amount is too large, workability tends to deteriorate and tan δ tends to increase. More preferably, the DBP absorption amount has a lower limit of 110 ml / 100 g or more and an upper limit of 130 ml / 100 g.

The rubber composition of the present invention contains 0 to 10 weight percent of silica having a BET specific surface area of 90 to 220 m ² / g and a DBP absorption of 120 to 220 ml / 100 g based on 100 parts by weight of the rubber component. It can mix | blend in part. That is, the silica is not essential, but when blended, it is preferably blended at 10 parts by weight or less. By blending the silica, tan δ can be lowered and the low heat build-up can be further improved. However, if the amount of silica exceeds 10 parts by weight, the workability deteriorates and the dispersibility of the silica is impaired, so that tan δ increases.

The BET specific surface area of silica is a value measured according to the BET method described in JIS K6430, more preferably 150 to 220 m ² / g, and still more preferably 180 to 210 m ² / g.

  The DBP absorption amount of silica is a value measured according to JIS K6217, and is more preferably 130 to 180 ml / 100 g which is 120 to 200 ml / 100 g.

  When silica is blended, it is preferable to use a silane coupling agent in combination. The compounding amount of the silane coupling agent is 5 to 15 parts by weight with respect to 100 parts by weight of silica, and if it is less than 5 parts by weight, the addition effect is insufficient and the dispersibility of silica is inferior. In the case of exceeding tan δ, tan δ deteriorates on the contrary due to an adverse effect of an excessive silane coupling agent that does not react with silica.

  The silane coupling agent is not particularly limited. For example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) Examples thereof include sulfide silanes such as tetrasulfide, and protected mercaptosilanes such as 3-octanoylthio-1-propyltriethoxysilane and 3-propionylthiopropyltrimethoxysilane.

  In addition to the above components, the rubber composition of the present invention is generally used in rubber compositions for tire treads such as zinc white, stearic acid, anti-aging agents, softeners, vulcanizing agents, and vulcanization accelerators. Various additives can be blended. The rubber composition is prepared by kneading according to a conventional method using a rubber kneader such as a normal Banbury mixer or kneader.

  The rubber composition for a tire tread of the present invention having the above-described configuration has an initial strain of 15%, a dynamic strain of ± 2.5%, a loss tangent tan δ of the vulcanizate measured at a frequency of 10 Hz and a temperature of 60 ° C. of 0.100 or less. It needs to be. When tan δ exceeds 0.100, the low heat build-up is inferior and the effect of reducing the fuel consumption of the pneumatic tire is insufficient. Note that the lower limit of tan δ is preferable from the viewpoint of low heat build-up, so the lower limit is not particularly limited, but is usually 0.050 or more.

  Since the tan δ of the vulcanizate varies depending on the blending amount of the high cis-butadiene rubber, the type and blending amount of the carbon black, the kind and blending amount of the silica, etc., as shown in Examples below. What is necessary is just to set these suitably so that it may become 0.100 or less. For example, tan δ increases as the amount of iodine adsorbed increases as the amount of adsorbed iodine increases, and as the amount of adsorbed carbon black increases. Tan δ can be set to 0.100 or less.

  The rubber composition for a tire tread of the present invention as described above is used as a rubber composition for a tread portion of a pneumatic radial tire, and the tread portion can be formed by vulcanization molding according to a conventional method. The rubber composition of the present invention is particularly suitable for treads of heavy duty tires used in large vehicles such as trucks and buses, but is not limited to this, and can be applied to passenger vehicle tires. it can.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

  Using a Banbury mixer, rubber compositions of Examples and Comparative Examples were prepared according to the formulations shown in Tables 1 and 2 below. Details of each formulation in Tables 1 and 2 are as follows.

NR: natural rubber (RSS # 3),
BR1: “BR150L” manufactured by Ube Industries, Ltd. (butadiene rubber polymerized with a cobalt catalyst, cis-1,4 bond content = 98.3%, vinyl group content = 0.7%, Mooney viscosity ML ( 1 + 4) 100 ° C. = 43),
BR2: “Buna CB22” manufactured by LANXESS (butadiene rubber polymerized with a neodymium catalyst, cis-1,4 bond content = 96.5%, vinyl group content = 0.4%, Mooney viscosity ML (1 + 4 ) 100 ° C = 63),
BR3: “Buna CB24” manufactured by LANXESS (butadiene rubber polymerized with a neodymium catalyst, cis-1,4 bond content = 96.7%, vinyl group content = 0.4%, Mooney viscosity ML (1 + 4 ) 100 ° C. = 44),
BR4: “Europrene NEOCIS BR60” manufactured by Polymeri Co., Ltd. (butadiene rubber polymerized by a neodymium catalyst, cis-1,4 bond content = 97.7%, vinyl group content = 0.4%, Mooney viscosity ML ( 1 + 4) 100 ° C. = 63).

CB1: “Seast 9” manufactured by Tokai Carbon Co., Ltd. (SAF, IA = 139 mg / g, DBP absorption amount = 115 ml / 100 g),
CB2: “Seast 6” manufactured by Tokai Carbon Co., Ltd. (ISAF, IA = 121 mg / g, DBP absorption amount = 114 ml / 100 g),
CB3: “Seast 7HM” manufactured by Tokai Carbon Co., Ltd. (ISAF, IA = 119 mg / g, DBP absorption amount = 123 ml / 100 g),
CB4: “Seast 3” manufactured by Tokai Carbon Co., Ltd. (HAF, IA = 80 mg / g, DBP absorption amount = 101 ml / 100 g).

Silica: “Nip seal AQ” (BET = 205 m ² / g, DBP absorption amount = 150 ml / 100 g) manufactured by Tosoh Silica Co., Ltd.
Silane coupling agent: “Si69” manufactured by Degussa.

  In each rubber composition, 3 parts by weight of zinc white (“Zinc Hana 1” manufactured by Mitsui Mining & Smelting Co., Ltd.) and stearic acid (“Lunac S25” manufactured by Kao Co., Ltd.) per 100 parts by weight of the rubber component are commonly blended. ) 1 part by weight, anti-aging agent (“Antigen 6C” manufactured by Sumitomo Chemical Co., Ltd.) 1 part by weight, vulcanization accelerator (“Soccele CZ” manufactured by Sumitomo Chemical Co., Ltd.) 1 part by weight, sulfur (Tsurumi Chemical Co., Ltd.) 2 parts by weight of “Powder Sulfur” manufactured by the company was blended.

  About each rubber composition, loss tangent tan-delta and abrasion resistance were measured using the test piece of the predetermined shape vulcanized at 150 degreeC for 30 minutes. Furthermore, using each rubber composition as a rubber for a tread, a pneumatic radial tire for a truck and bus (tire size: 11R22.5 14PR) was produced, and rolling resistance was evaluated. Each evaluation / measurement method is as follows.

Loss tangent tan δ: Tan δ was measured under the conditions of an initial strain of 15%, a dynamic strain of ± 2.5%, a frequency of 10 Hz, and a temperature of 60 ° C. using a viscoelastic spectrometer manufactured by UBM.

Abrasion resistance: In accordance with JIS K6251, the wear resistance was measured under the conditions of a slip rate of 30%, a load load of 40 N, and a sandfall amount of 20 g / min, and displayed as an index with the value of Comparative Example 1 being 100. . The higher the value, the better the wear resistance.

Rolling resistance: Using a single-axis drum tester, the rolling resistance when running on a drum at an internal pressure of 800 kPa, a load of 2900 kg, and a speed of 60 km / h was measured and displayed as an index with the tire of Comparative Example 1 as 100. . Smaller values indicate lower rolling resistance and better fuel economy.

  The results are as shown in Tables 1 and 2. In Comparative Examples 1 to 3, which are controls, butadiene rubber having a high vinyl group content polymerized with a cobalt-based catalyst is used, so tan δ is high and fuel efficiency is reduced. It was inferior. In Comparative Examples 4 and 5, since the HAF class having a low iodine adsorption amount was used as carbon black, the wear resistance was poor.

  In Comparative Example 6, although butadiene rubber polymerized with a neodymium catalyst was used, the amount of carbon black was too large, so tan δ was high, fuel efficiency was inferior, and processability was also deteriorated. In Comparative Example 7, although butadiene rubber polymerized with a neodymium-based catalyst was used, the amount of carbon black was too small, so the wear resistance was poor.

  In Comparative Example 8, butadiene rubber polymerized with a neodymium catalyst was used, but the amount of silica was too large, so tan δ was high and processability was also deteriorated. In Comparative Example 9, although butadiene rubber polymerized with a neodymium catalyst was used, the amount of the silane coupling agent was too large, so tan δ was high and the fuel efficiency was poor.

  In Comparative Example 10, since the rubber component was natural rubber alone, the wear resistance was poor. In Comparative Example 11, since the blending amount of the butadiene rubber polymerized with the neodymium catalyst was too large, tan δ was high, the workability was deteriorated, and the tire production was at a very difficult level, so the rolling resistance was evaluated. Was not implemented.

  On the other hand, in Examples 1 to 11 according to the present invention, tan δ can be lowered and low heat build-up can be improved while suppressing a decrease in wear resistance. I was able to achieve both.

  The rubber composition for tire tread of the present invention can be used for various pneumatic tires such as passenger cars, light trucks, trucks and buses.

Claims (3)

A butadiene rubber synthesized by using 60 to 90 parts by weight of natural rubber and / or isoprene rubber and a neodymium catalyst, having a cis-1,4 bond content of 96% or more and a vinyl group content of 0.6. % Relative to 100 parts by weight of a rubber component containing 40 to 10 parts by weight of butadiene rubber,
Containing 35 to 55 parts by weight of carbon black having an iodine adsorption of 105 to 165 mg / g and a DBP absorption of 95 to 145 ml / 100 g;
A rubber composition for a tire tread, wherein a loss tangent tan δ of a vulcanizate measured at an initial strain of 15%, a dynamic strain of ± 2.5%, a frequency of 10 Hz, and a temperature of 60 ° C. is 0.100 or less. 10 parts by weight or less of silica having a BET specific surface area of 90 to 220 m ² / g and DBP absorption of 120 to 220 ml / 100 g with respect to 100 parts by weight of the rubber component, and a silane coupling agent to 100 parts by weight of silica The rubber composition for a tire tread according to claim 1, further comprising 5 to 15 parts by weight.   A pneumatic tire comprising a tread portion made of the rubber composition according to claim 1.