JP2002088193A - Rubber composition for tread - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a rubber composition capable of providing compatibly excellent wetting performance and rolling resistance to a tire, and having good processability in a kneading. SOLUTION: This rubber composition for treads is obtained by compounding 100 pts.wt. of a diene-based rubber with 30-90 pts.wt. of silica as the filler and 2-20 pts.wt. of a polyethylene glycol; wherein 100 pts.wt. of the diene-based rubber contains >=10 pts.wt. of a styrene/isoprene/butadiene terpolymer having a glass transition temperature of -80 to -10 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tread rubber composition, and more particularly to a tread rubber composition excellent in processability, wet performance and rolling resistance.

[0002]

2. Description of the Related Art To improve the wet performance (grip and braking distance in steering stability) of a tire, generally,
A method of using silica as a filler in a tread rubber composition and a method of increasing hysteresis at a low temperature are known.

[0003] One effective method for increasing hysteresis at low temperatures is to use a rubber composition having a high glass transition temperature. However, a rubber composition having a high glass transition temperature can improve the wet performance, but at the same time, has a problem that the hysteresis at a high temperature increases to increase the rolling resistance, and the abrasion resistance tends to decrease. As a technique for solving this problem, Japanese Patent Laid-Open No.
No. 79667 describes a method of using a styrene / isoprene / butadiene terpolymer (SIBR) in a rubber composition. According to this method, the rolling resistance,
Although wet traction and abrasion resistance can be slightly improved, it is difficult to achieve a balance between wet performance and rolling resistance in a high dimension, and there is no mention of workability.

[0004] When silica is frequently used as a filler in a rubber composition, dispersion of the silica during kneading becomes difficult, and a problem remains in processability. In a rubber composition highly filled with silica as described above, the compatibility of wet performance and rolling resistance in a high dimension, including workability, is a trade-off, but the viewpoint of ensuring safety and improving the environment during automobile driving in rainy weather Therefore, a quick improvement method is required.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a tread rubber composition highly filled with silica that satisfies wet performance and rolling resistance at a high level and improves workability during kneading. It is in.

[0006]

According to the present invention, a filler, silica 30 to 90, is added to 100 parts by weight of a diene rubber.
Parts by weight and polyethylene glycol (PEG) 2-2
0 parts by weight, and the diene rubber 100
Of the parts by weight, at least 10 parts by weight of a tread rubber composition which is a styrene / isoprene / butadiene terpolymer (SIBR) having a glass transition temperature of -80 to -10 ° C, and a PEG having a number average molecular weight of 200 to 6000. It relates to the above-mentioned tread rubber composition.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The tread rubber composition of the present invention comprises:
Styrene / isoprene / butadiene terpolymer (SI
It is composed of a diene rubber containing BR), silica and polyethylene glycol (PEG).

[0008] The compounding amount of SIBR is 100 parts of diene rubber.
It is at least 10 parts by weight, preferably at least 20 parts by weight of the parts by weight. If the amount of SIBR is less than 10 parts by weight, it is difficult to improve the wet performance.

The glass transition temperature of SIBR is -80.
To -10C, preferably -60 to -20C. SI
When the glass transition temperature of the BR is less than -80 ° C, the grip performance of the tire decreases, and when it exceeds -10 ° C, the wear resistance and the snow performance deteriorate.

The arrangement of styrene units, isoprene units and butadiene units in SIBR may be random or block.

The tread rubber composition of the present invention comprises, as rubber components, styrene-butadiene rubber (SBR), butadiene rubber (BR), 1,4-added isoprene rubber (IR), ethylene-propylene-diene rubber in addition to SIBR. (EPDM), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), natural rubber (N
At least one of diene rubbers other than SIBR such as R) can be included. The glass transition temperature of these diene rubbers is preferably from -80 to -10C. If the glass transition temperature is less than -80 ° C, grip performance tends to be poor, and if it exceeds -10 ° C, abrasion resistance and snow performance tend to decrease.

[0012] The rubber composition of the present invention contains silica as a filler. The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably from 50 to 300 m ² / g. Nitrogen adsorption specific surface area (N ₂ SA) of the silica of less than 50 m ² / g tend dispersibility improving effect and the reinforcing effect is small, 300 meters ² /
If the silica exceeds g, the dispersibility is poor, and the heat buildup of the tire tends to increase.

The silica is not particularly limited. Dry silica (anhydrous silicic acid), wet silica (hydrous silicic acid) and the like can be used, and wet silica is preferably used. Particularly suitable wet-process silicas include, for example, Ultrasil V manufactured by Degussa.
N3 (trade name), Nip Seal VN3 AQ (trade name) manufactured by Nippon Silica Industry Co., Ltd., and the like.

The amount of the silica is 30 to 90 parts by weight, preferably 40 to 7 parts by weight, based on 100 parts by weight of the diene rubber.
0 parts by weight. If the amount of silica is less than 30 parts by weight, wet performance and reinforcing property tend to be poor, and if more than 90 parts by weight, the viscosity at the time of kneading becomes high and the workability tends to decrease.

The compounding amount of PEG contained in the rubber composition of the present invention is 2 to 20 parts by weight based on 100 parts by weight of the diene rubber.
Parts by weight, preferably 2 to 10 parts by weight. If the amount of PEG is less than 2 parts by weight, no improvement in performance can be expected in terms of wet performance, rolling resistance and viscosity reduction, and if it exceeds 20 parts by weight, the scorch time will be short.

The number average molecular weight of PEG is from 200 to 600.
It is preferably 0, particularly preferably 400 to 6000.
If the number average molecular weight of PEG is less than 200, the wear resistance of the tire tends to decrease, and if it exceeds 6000, the reduction in rolling resistance tends to decrease.

The rubber composition of the present invention may contain a silane coupling agent in addition to the above components. The silane coupling agent is not particularly limited as long as it has been conventionally used in the field of tires. For example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-trimethoxysilylpropyl)
Examples thereof include tetrasulfide, bis (2-triethoxysilylpropyl) tetrasulfide, 3-mercaptopropyltriethoxysilane, and 2-mercaptoethyltrimethoxysilane, and these can be used alone or in any combination. . Among these, bis (3-triethoxysilylpropyl) tetrasulfide and 3-mercaptopropyltriethoxysilane are preferably used from the viewpoint of the reinforcing effect and processability of the silane coupling agent, and further, from the viewpoint of processability. It is particularly preferable to use bis (3-triethoxysilylpropyl) tetrasulfide.

The compounding amount of the silane coupling agent is 2 to 2 of silica in terms of sufficient coupling.
It is preferably 20% by weight, and more preferably 4 to 15% by weight from the viewpoint of preventing a reduction in workability.

The rubber composition of the present invention may contain carbon black as a filler in addition to the silica. As carbon black, there is no particular limitation,
For example, there are HAF, ISAF, SAF, and the like.

The compounding amount of carbon black is preferably 10 to 70 parts by weight based on 100 parts by weight of the diene rubber. If the compounding amount of carbon black is less than 10 parts by weight, dry performance and reinforcing property tend to decrease, and if it exceeds 70 parts by weight, rolling resistance tends to increase.

The rubber composition of the present invention may further comprise, in addition to the above-mentioned components, a softening agent such as a paraffinic, aroma-based, or naphthenic-based process oil; and a tackifier such as a coumaroindene resin, a rosin-based resin, or a cyclopentadiene-based resin. Vulcanizing agents such as sulfur and peroxide; vulcanization accelerators; vulcanization aids such as stearic acid and zinc oxide;
It can be appropriately compounded as needed as long as the effects of the present invention are not impaired.

The rubber composition of the present invention can be used as a tread of a tire. The tire is manufactured by a usual method. That is, the rubber composition according to the present invention, into which various chemicals are blended as required, is extruded into a tread member at an unvulcanized stage, and is pasted and molded by a usual method on a tire molding machine to obtain an uncured material. Mold sulfur tires. The unvulcanized tire is heated and pressed in a vulcanizer to obtain a tire. The tire thus obtained has wet performance,
Excellent rolling resistance.

[0023]

EXAMPLES The present invention will now be described specifically with reference to examples, but the present invention is not limited to these examples.

Examples 1 to 6 and Comparative Examples 1 to 8 Each component other than sulfur and the vulcanization accelerator shown in Table 1 was used.
After kneading at about 150 ° C. for 4 minutes using a 1.7 L Banbury mixer manufactured by Kobe Steel, Ltd., sulfur and a vulcanization accelerator were added, and the mixture was kneaded at 80 ° C. for about 4 minutes with a biaxial roller. The resulting mixture was vulcanized at 175 ° C for 10 minutes to prepare a tread rubber composition. In addition, diene rubber (SBR (Nippol 9520)), SIBR (glass transition temperature about -30 ° C, styrene unit amount 25 wt%,
The amount of isoprene unit 50% by weight, butadiene unit amount 25% by weight) and the amount of PEG were varied according to Tables 2 and 3. The following test was performed on the obtained tread rubber composition.

[0025]

[Table 1]

Test method (1) Mooney viscosity and scorch time According to JIS K6300, Mooney viscosity and scorch time were measured at 130 ° C. using MV202 manufactured by Shimadzu Corporation. The lower the value of the Mooney viscosity, the better the workability. If the scorch time is less than 10 minutes, rubber scorch will occur, which is not preferable.

(2) Measurement of Viscoelasticity Using a VES-F-3 manufactured by Iwamoto Seisakusho, the loss tangent (tan δ) at 60 ° C. was measured at a frequency of 10 Hz, an initial strain of 10%, and a dynamic strain of 2%. The smaller the tan δ value, the more advantageous the rolling resistance.

(3) Abrasion resistance Abrasion resistance was measured with a measuring device manufactured by Iwamoto Seisakusho Co., Ltd. under a load of 3.0 kg and a slip ratio of 30%. The evaluation was represented by an index with the case of Comparative Example 1 taken as 100. The larger the index, the better the wear resistance performance.

(4) Wet performance A tire of 185 / 70R14 size is manufactured by a conventional method, and a normal passenger car equipped with the tire makes a circular turn and slips on a test course on an asphalt road surface on which water is sprayed. The maximum speed was measured, and the wet performance was evaluated by an index with the case of Comparative Example 1 as 100. The higher the index, the better the wet performance.

The test results are shown in Tables 2 and 3.

[0031]

[Table 2]

[0032]

[Table 3]

Table 2 shows the results of the variation test of SIBR and PEG600, and Table 3 shows the results when the number average molecular weight of PEG was changed.

Comparative Examples 2 to 4 in Table 2 show that SIB
R is mixed in a variable amount. In Comparative Example 2 in which the amount of SIBR was 5 parts by weight, no improvement in various performances could be expected. The amount of SIBR was 50 parts by weight and 80 parts by weight, respectively.
In Comparative Examples 3 and 4, which are parts by weight, the wet performance and the wear resistance were able to be improved. However, since PEG was not blended, rolling resistance and Mooney viscosity could not be reduced at the same time.

On the other hand, Comparative Examples 5 to 7 in Table 2 show that Comparative Example 1 was blended with a variable amount of PEG. It is believed that PEG coats the silica and prevents the vulcanization accelerator from adsorbing to the silica. As a result, it is considered that effective vulcanization is performed, the crosslink density increases, and tan δ decreases. Moreover, since PEG coats silica, aggregation of silica is prevented, and Mooney viscosity is reduced.

Among Comparative Examples 5 to 7, the most balanced in terms of processability and rolling resistance was Comparative Example 6 in which 5 parts by weight of PEG 600 was blended. PEG600 is 1
In Comparative Example 5 which is part by weight, tan δ was not reduced, and Mooney viscosity was not significantly reduced. In Comparative Example 7, in which PEG 600 was 25 parts by weight, tan δ and Mooney viscosity were reduced, but the scorch time was considerably shortened, which was not preferable in view of workability. Mooney viscosity and ta
It can be seen that the composition in which nδ was reduced and the scorch time was at a practical level was Comparative Example 6 in which PEG 600 was 5 parts by weight. However, since SIBR is not compounded,
We could not expect much improvement in wet performance.

In Examples 1 to 3 in which SIBR and PEG 600 were simultaneously blended, the wet performance, rolling resistance and workability could be improved at a high level. Among them, it can be seen that Example 2 is the most balanced and effective.

From the results of Examples 2, 4, 5, 6 and Comparative Example 8 in Table 3 in which the number average molecular weight of PEG was changed, the number average molecular weight of PEG is preferably from 200 to 6000.
It can be seen that Example 2 using 00 is the most balanced. That is, as compared with Example 6 using PEG11000, PEG600, PEG200 and PE
In Examples 2, 4 and 5 using G6000, tan δ
It can be seen that the rolling resistance is further reduced. In Comparative Example 8 using ethylene glycol, the abrasion resistance performance was reduced, and the molecular weight was small, so that bloom was easily caused, which is not preferable.

[0039]

According to the present invention, a silica-containing tread rubber composition having both high wet performance and high rolling resistance can be obtained, and a rubber composition having good processability during kneading can be obtained. be able to.

Claims (2)

[Claims] 1. A rubber composition comprising 30 to 90 parts by weight of silica and 2 to 20 parts by weight of polyethylene glycol as a filler with respect to 100 parts by weight of a diene rubber. -8 for parts by weight or more
A tread rubber composition that is a styrene / isoprene / butadiene terpolymer having a glass transition temperature of 0 to -10C. 2. The tread rubber composition according to claim 1, wherein the polyethylene glycol has a number average molecular weight of 200 to 6,000.