JP2007186567A - Rubber composition for tread of tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for the tread of a tire, improving its dry and wet steering stability, a low temperature performance and processability without damaging its low fuel consumption property. <P>SOLUTION: This rubber composition obtained by blending 30-150 pts.wt. reinforcing filler containing ≥10 pts.wt. silica having 100-300 m<SP>2</SP>/g BET specific surface area and 0.1-15 wt.% silane coupling agent based on the silica blending amount, with 100 pts.wt. diene-based rubber is provided by blending 1-20 pt./pts.wt. total blending amount of (1) a terpene resin having a Tg: 50 to 120°C and (2) (a) a terpene-based liquid resin having hydroxyl value: ≤120 mg/KOH and (b) at least one kind of a rosin ester compound obtained by reacting the rosin having a Tg: -50 to 10°C with an ester, by a blending ratio of (1):(2)=(20:80) to (80:20) range. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a rubber composition for a tire tread, and more particularly, to a rubber composition for a tire tread having improved dry and wet handling stability, low temperature performance, and processability without impairing low fuel consumption.

  Today, silica compound rubber compound is positioned as a technology that achieves both low fuel consumption and rain safety (wet performance), and various researches have been conducted by tire manufacturers. As basic problems, there are a decrease in dry performance and a decrease in workability due to re-aggregation of silica. In addition, recently, from the viewpoint of environmental protection, the problem of scattering of petroleum-based aroma oil, which has been conventionally used as a plasticizer for tire rubber, into the atmosphere accompanying tire wear has been pointed out.

  Conventionally, a rubber composition for studless tires with improved wear resistance on ice and snowy road surfaces while maintaining wear resistance at a high level, resin powder, polynorbornene elastomer and terpene resin are added to diene rubber. A compounding technique is disclosed in the following Patent Document 1, and a rubber composition for a tire tread having improved grip properties on snow, on ice, or a wet road surface, and a softening agent-containing norbornene polymer in a diene rubber And a technique for blending a terpene resin or rosin ester as a tackifier is disclosed in the following Patent Document 2, and further, the tire tread that achieves both wet grip performance and wear resistance by increasing the strength of the butyl rubber. Terpene resin and rosin for diene rubber such as SBR Art of compounding resin butter, and the like is disclosed in Patent Document 3 below.

  Further, in order to obtain a tire tread rubber composition excellent in both workability and grip performance in relation to the first problem described above, 10 to 150 parts by weight of a terpene resin having a softening point of 80 to 160 ° C. The prior art blended into the diene rubber in an amount of 5 is disclosed in Patent Document 4 below, and in relation to the first and second problems, the tire tread rubber is excellent in workability and low rolling resistance. In order to obtain a composition, a non-petroleum high glass transition temperature (Tg) glycerol fatty acid triester is used as a base, and a plasticizer further containing a small amount of vegetable oil, if necessary, a large amount silica compounded diene rubber composition The prior art which mix | blends a predetermined quantity with is disclosed by the following patent documents 5. FIG.

JP 2001-302847 A JP-A-11-246711 JP 2004-2584 A JP 2004-18760 A Special table 2004-519551 gazette

  The present invention has been made in view of the solution of the above-mentioned problems. By blending a high Tg and low Tg resin component into a silica compounded rubber composition, the fuel efficiency of the silica compounded rubber composition is improved. An object of the present invention is to provide a rubber composition for a tire tread having improved dry and wet handling stability, low temperature performance, and processability without impairing the performance.

According to the present invention, 30 to 150 parts by weight of a reinforcing filler containing 10 parts by weight or more of silica having a BET specific surface area of 100 to 300 m ² / g with respect to 100 parts by weight of diene rubber, and the amount of silane coupling agent added to silica In the rubber composition for a tire tread formed by blending 0.1 to 15% by weight with respect to
(1) Tg: terpene resin having a temperature of 50 to 120 ° C. At least one kind of rosin ester compound obtained by reacting rosin and ester at 10 ° C. is in the range of blending ratio (1) :( 2) = 20: 80-80: 20, and the total blending amount is 1-20 wt. A partially blended rubber composition for tire treads is provided.

  In the present invention, the problem of deterioration in processability and dry performance in the silica compounded rubber composition is that a high Tg terpene resin and a low Tg terpene liquid resin and / or a low Tg rosin ester have a predetermined compounding ratio. Thus, it has been found that a predetermined amount can be solved at once by blending with a silica-blended rubber composition.

  As said high Tg terpene resin mix | blended with the rubber composition for tire treads of this invention, Tg: 50-120 degreeC, More preferably, the terpene resin of 60-100 degreeC is used. As such a terpene resin, a terpene resin, a hydrogenated terpene resin, a terpene phenol resin, an aromatic modified terpene resin, or the like is selected and used.

  The low Tg (a) terpene-based liquid resin blended in the tire tread rubber composition of the present invention has a Tg of −50 to 10 ° C., more preferably −40 to 0 ° C., and a hydroxyl value: A terpene-based liquid resin of 120 mg / KOH or less, preferably 100 mg / KOH or less is used. As such terpene-based liquid resin, for example, a terpene resin, a hydrogenated terpene resin, a terpene phenol resin, an aromatic modified resin, or the like is selected and used.

  In addition, the low Tg (b) rosin ester compound blended in the tire tread rubber composition of the present invention has a Tg of -50 to 10 ° C, more preferably -40 to 0 ° C. A compound is used. Examples of such rosin ester compounds include (a) rosins such as tall oil, tall oil resin and tall oil fatty acid, and (b) various monovalent or polyhydric alcohols (among these, preferred ones are: Ester compounds with ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, etc.) are used.

  In the tire tread rubber composition of the present invention, the blend ratio of the high Tg terpene resin and at least one of the low Tg (a) terpene liquid resin and (b) rosin ester compound is 20:80. -80: 20, more preferably in the range of 30: 70-70: 30, with respect to 100 parts by weight of the diene rubber composition, the total blending amount is 1-20 parts by weight, more preferably 1.5-15 parts by weight. Is used in an amount of. When the blending ratio of the high Tg terpene resin is less than 20 or more than 80, the balance between the dry performance and the wet performance is deteriorated, and the workability improvement effect is small, which is not preferable. If the total amount is less than 1 part by weight, the desired effect cannot be exhibited. Conversely, if it exceeds 20 parts by weight, heat generation (low fuel consumption) and wear resistance are deteriorated, which is not preferable.

  Examples of the diene rubber component used in the tire tread rubber composition of the present invention include natural rubber (NR), polyisoprene rubber (IR), various butadiene rubbers (BR), and various styrene-butadiene copolymers. Rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), chloroprene rubber, ethylene-propylene-diene copolymer rubber, styrene-isoprene copolymer rubber, styrene-isoprene-butadiene copolymer rubber, isoprene-butadiene Synthetic rubbers such as copolymer rubbers may be mentioned, and the rubber components may be used alone or in admixture of two or more.

As the reinforcing filler blended in the rubber composition for tire treads of the present invention, the reinforcing filler 30 containing 10 parts by weight or more, preferably 20 to 100 parts by weight of silica having a BET specific surface area of 100 to 300 m ² / g. Up to 150 parts by weight, preferably 40 to 120 parts by weight are used. If the compounding amount of the silica is less than 10 parts by weight, a low heat-generating rubber composition cannot be obtained. Conversely, if the compounding amount of the reinforcing filler containing silica exceeds 150 parts by weight, the workability and wear resistance are reduced. This is not preferable because the properties and the like are lowered. As the reinforcing filler other than silica, usually, carbon black or the like is preferably used, but is not limited thereto.

  In the rubber composition for a tire tread of the present invention, a silane coupling agent that is usually blended with silica is blended and used in an amount of 0.1 to 15% by weight, preferably 4 to 10% by weight of the blended amount of silica. As such a silane coupling agent, any of the silane coupling agents generally used in the tire rubber composition may be used alone or in combination.

  The rubber composition for a tire tread of the present invention is further added with a usual vulcanization or crosslinking agent, a vulcanization or crosslinking accelerator, an anti-aging agent, a filler, a plasticizer, and other various compounding agents blended for tire rubber. The compounding agent can be kneaded by a general method to obtain a rubber composition, which can be vulcanized or crosslinked. The compounding amounts of these compounding agents can be set to conventional general compounding amounts as long as the object of the present invention is not violated.

The ester compound of rosin (diethylene glycol ester of tall oil) used in Examples and Comparative Examples of the present invention was obtained by the following preparation method.
Preparation of tall oil diethylene glycol ester A four-necked flask equipped with a stirrer, nitrogen inlet tube, thermometer, Dean-Stark water separator, tall oil (45% fatty acid, 38% rosin, acid value 157, trade name: Hartle) SR-30, Harima Chemicals) 1500 g, diethylene glycol 265 g (OH / COOH = 1.2), and magnesium oxide 1.8 g were added. After stirring and homogenizing, the temperature was raised to 200 ° C., and esterification was performed at the same temperature for 10 hours. Thereafter, unreacted alcohol and the like were removed under reduced pressure to obtain diethylene glycol ester of tall oil.

Preparation of test sample The components other than the vulcanization accelerator and sulfur in the composition shown in Table 1 below were kneaded for 5 minutes in a 1.7 L closed Banbury mixer, and released to the outside of the mixer when the temperature reached 160 ° C. After cooling to room temperature, this master batch was put into the mixer, and a vulcanization accelerator and sulfur were blended and kneaded to obtain a rubber composition. A part of this rubber composition was subjected to an extrudability test. The remaining rubber composition was press vulcanized at 160 ° C. for 20 minutes in a 15 × 15 × 0.2 cm mold to obtain a test piece (rubber sheet), which was subjected to a rolling resistance test and a low temperature performance test. .

Preparation of test tire A rubber composition part comprising the compounding composition of each example shown in Table 1 was obtained in the same manner as described above, and this was extruded as a cap tread to prepare a test tire of 195 / 65R15 size. It was subjected to a stability test.

Test Method 1) Extrudability: When the cap tread was extruded, the screw rotation speed of the extruder after the extrudate width / gauge was stabilized to a predetermined dimension was indicated by an index with Comparative Example 1 as 100. A larger index indicates better extrudability.
2) Rolling resistance: Using a viscoelastic spectrometer (manufactured by Toyo Seiki Seisakusho Co., Ltd.), at a temperature of 60 ° C., initial strain: 10%, dynamic strain: ± 2%, frequency 20 Hz, tan δ (60 ° C.) Measured and displayed as an index with Comparative Example 1 as 100. It shows that rolling resistance is excellent, so that a numerical value is large.

3) Dry handling stability: Test tires with the same specifications are mounted on a test vehicle with a displacement of 2L, and the grip level and steering performance on a dry paved road surface are evaluated. Comparative Example 1 is set to 100. Expressed as an index. It shows that dry steering stability is so favorable that a numerical value is large.
4) Wet handling stability: Test tires with the same specifications are mounted on a test vehicle with a displacement of 2 liters, and the grip level and steering performance on a wet road with a water depth of 2 mm are evaluated for feeling. Expressed as an index. It shows that wet steering stability is so favorable that a numerical value is large.
5) Low temperature performance: Measured under conditions of on-ice temperature (temperature: -3 ° C) using a British portable skid tester. It shows that low temperature performance is excellent, so that a numerical value is large.

Examples 1-5 and Comparative Examples 1-4
The results are shown in Table 1 below.

  According to the results of Table 1, in the rubber composition of the present invention in which a high Tg terpene resin and at least one of a low Tg terpene-based liquid resin and / or an ester compound of rosin are combined, a low rolling resistance is maintained. It can be seen that dry and wet handling stability, low temperature performance, and processability are improved.

  Therefore, the rubber composition of the present invention is extremely useful as a rubber composition for tire treads.

Claims (1)

30 to 150 parts by weight of a reinforcing filler containing 10 parts by weight or more of silica having a BET specific surface area of 100 to 300 m ² / g with respect to 100 parts by weight of the diene rubber, and 0.1% of the silane coupling agent relative to the amount of silica. In the rubber composition for a tire tread formed by blending ~ 15% by weight,
(1) Tg: terpene resin having a temperature of 50 to 120 ° C. At least one kind of rosin ester compound obtained by reacting rosin and ester at 10 ° C. is in the range of blending ratio (1) :( 2) = 20: 80-80: 20, and the total blending amount is 1-20 wt. A rubber composition for a tire tread, characterized in that it is partially blended.