JPH07278353A - Rubber composition, tire tread produced from the composition and tire furnished with the tread - Google Patents

Abstract

PURPOSE:To provide a rubber composition containing a specific rubber component and silica at a specific ratio, having excellent abrasion resistance and low rolling resistance (low fuel cost) and suitable for tire tread, etc. CONSTITUTION:This rubber composition contains (A) 100 pts.wt. of a rubber component containing >=30wt.% of an isoprene-butadiene copolymer (having a glass transition temperature of preferably -90 to +20 deg.C) composed of 30-90wt.% of butadiene and the remaining part of isoprene and (B) 20-90 pts.wt. of silica having a BET surface area of 100-250m<2>/g. The butadiene in the isoprene-butadiene copolymer preferably contains 10-70wt.% of 1,2-bonded component and the isoprene preferably contains 20-70wt.% of 3,4-bonded component.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a rubber composition containing silica as a filler and having improved rolling resistance without lowering abrasion resistance, a tread prepared by using the rubber composition, and the tread. A tire having

[0002]

BACKGROUND OF THE INVENTION It is difficult to achieve the desired properties of a tire at the same time.
This is because the above properties are partially contrary to each other. That is, a measure for reducing rolling resistance leads to a reduction in wear resistance. For example, by substituting silica for all or part of carbon black as a filler, the rolling resistance of the tire is reduced, but the wear resistance of the tire is reduced. European Patent Publication No. 299074 discloses that a polymer modified with a special silane compound is used for a rubber composition containing a large amount of carbon black as a filler in order to prevent deterioration of wear resistance. Although proposed, this measure is unsuitable for industrial use because it uses a special silane compound.

To avoid this drawback, European Patent Publication No. 501227 discloses conjugated diene-vinyl aromatic compound copolymers synthesized by solution polymerization in a hydrocarbon solvent, and European Patent Publication No. 157703, for example. Special silica prepared by the method described, and conventional additives,
A rubber composition containing a vulcanization system has been proposed. The rubber composition is prepared in a known manner by stepwise mixing of the components. The compounding is performed at a temperature at which crosslinking does not occur. At least one other diene-based rubber component (eg, polyisoprene, natural rubber or polybutadiene) can be added to the rubber composition as a filler.

In the examples and comparative examples of the above publications, a styrene-butadiene copolymer synthesized by emulsion polymerization (hereinafter referred to as "emulsion polymerization SBR") and special silica or known silica as a filler or A styrene-butadiene copolymer (hereinafter, referred to as "solution polymerization SBR") synthesized by mutually comparing tire treads produced from a rubber composition containing carbon black or by solution polymerization, and a special silica as a filler. Alternatively, tire treads made from a rubber composition containing carbon black are compared with each other. As is apparent from the presented results, the tread containing emulsion polymerized SBR and carbon black has good wear resistance, but poor rolling resistance. Treads containing emulsion polymerized SBR and known silicas have poor wear resistance, but instead have good rolling resistance. And European Patent Publication 501227
The claimed tread, i.e. a tread containing solution-polymerized SBR and special silica, gave good results in both rolling resistance and abrasion resistance. However, this tread still uses special silica.

The object of the present invention is to provide abrasion resistance even in a tire tread made of a rubber composition containing a known silica without using a special silane compound or silica as proposed in the above European Patent Publication. And to provide a rubber composition which gives good results on rolling resistance.

[0006]

That is, the rubber composition of the present invention contains 2 parts of silica based on 100 parts by weight of the rubber component.
A rubber composition containing 0 to 90 parts by weight, wherein at least 30% by weight or more of the rubber component is an isoprene-butadiene copolymer or an isoprene-butadiene-styrene terpolymer.

That is, the rubber component in the rubber composition of the present invention is 30 to 100% by weight, preferably 50 to 10%.
0% by weight, more preferably 70 to 100% by weight, is a specific copolymer, namely isoprene-butadiene-styrene or isoprene-butadiene-styrene terpolymer. The isoprene-butadiene copolymer used in the present invention preferably has a glass transition temperature (Tg) in the range of -90 ° C to 20 ° C measured by a torsion pendulum method. Specifically, the isoprene-butadiene copolymer is
30-90% by weight of butadiene, preferably 60-80
It is preferred that the balance consists of isoprene, in weight percent.
Further, butadiene in the isoprene-butadiene copolymer preferably has 10 to 70% by weight of 1,2-bond component, and isoprene preferably contains 20 to 70% by weight of 3,4-bond component. The balance is the 1,4-bond component of isoprene and butadiene.

The glass transition temperature of the isoprene-butadiene-styrene terpolymer according to the present invention is in the range of -90 ° C to 20 ° C as measured by the torsion pendulum method. Specifically, the terpolymer preferably comprises 5 to 30 wt% isoprene, 40 to 80 wt% butadiene, and 15 to 30 wt% styrene. Particularly, in the terpolymer, 10 to 20% by weight of isoprene, 60 to 80% by weight of butadiene,
It is preferably composed of 15 to 30% by weight of styrene. Further, butadiene constituting the terpolymer has 20 to 70% by weight of 1,2-bond component, and isoprene is 40 to 6%.
It is preferred to have 0% by weight of 3,4-bond component.
Further, the butadiene constituting the terpolymer is 25 to 3
It has 5% by weight of 1,2-bond component and isoprene 55
More preferably, it has a 3,4-bond content of ˜60% by weight.

The rubber component of the rubber composition according to the present invention includes
Other than the specific rubber component, other rubber component may be contained in an amount of 0 to 70% by weight. As other rubber components, for example, natural rubber, a conjugated diene-vinyl aromatic compound copolymer synthesized by emulsion polymerization (hereinafter, referred to as "emulsion polymerization-conjugated diene-
Vinyl aromatic compound copolymer "), polybutadiene, or any combination thereof. Specifically, out of 100 parts by weight of all rubber components, natural rubber 0-5
0 parts by weight, emulsion polymerization-conjugated diene-vinyl aromatic compound copolymer 0 to 50 parts by weight, polybutadiene 0 to 30 parts by weight, or any combination thereof may be contained.

In the emulsion polymerization-conjugated diene-vinyl aromatic compound copolymer, 1,3-butadiene, isoprene and 2,3-dimethyl-1,3-butadiene are preferably used as the conjugated diene. To be Vinyl aromatic compounds include styrene, o-, m-, p
-Methylstyrene is preferably used. Among them, the emulsion polymerization-conjugated diene-vinyl aromatic compound copolymer is a styrene-butadiene copolymer (emulsion polymerization SBR) having a glass transition temperature of −20 to −70 ° C. determined by the torsion pendulum method. Preferably there is. As the polybutadiene, there are many 1,4-cis-bond components,
In particular, it is preferable to use polybutadiene having a 1,4-cis-bond component of more than 90%.

The rubber component can be used in the form of oil-extended rubber.
Generally, the total amount of oil of the rubber composition, that is, the free oil and the oil content of the rubber component is 1 per 100 parts by weight of the total rubber component.
It is preferably in the range of 0 to 50 parts by weight. The rubber composition according to the present invention contains silica as a filler in an amount of 20 to 90 parts by weight, preferably 5 parts by weight, based on 100 parts by weight of all rubber components.
Including 0 to 80 parts by weight. As silica, “conventional silica” and silica having optimized dispersibility in a rubber composition can be used. "Conventional" silica is understood as the silica that is commercially available from the respective manufacturers and is customary for tire manufacturing. Such silicas typically have a BET surface area (DI
N66131, see ISO5794 / 1 Annex D) 100-250 m ² / g, CTAB surface area (ISO
6810, ASTM D-3765) 100-25
0 m ² and DBP oil absorption (ISO S-4656, A
STM D-2414, DIN53601) 150-2
Having 50 ml / 100 g. Examples of silica having optimized dispersibility include European Patent Publication No. 15770.
Silica as described in No. 3 can be used.

The rubber composition according to the present invention may contain carbon black as another filler. The carbon black content must not exceed the silica content and the total amount of fillers must not exceed 90 parts by weight with respect to 100 parts by weight of the total rubber component. Incidentally, carbon black may also be contained as a reinforcing material. The rubber composition according to the present invention may contain, as conventional additives, aromatic oils and / or naphthenic oils, reinforcing materials, antioxidants, tackifiers, activators and processing aids. All these additives can be incorporated in the usual amount ranges. When a part of silica is replaced with carbon black, it is preferable to add a small amount of reinforcing material. Further, the rubber composition according to the present invention may contain a vulcanization system containing sulfur and a vulcanization accelerator.

The rubber composition according to the present invention has the above composition and can be prepared by the following multi-step method. In the first stage, one or more rubber components are mixed with conventional additives and silica in a kneader. In this case, the temperature should not rise to a temperature at which crosslinking begins, and the temperature should usually not exceed 160 to 170 ° C. After cooling, the mixture is further kneaded in the second stage. Also in this stage, as in the case of the first stage, the temperature should not be raised to the temperature at which crosslinking starts. In the next third stage, the vulcanization system is incorporated in rolls. Also in this case, the temperature is kept below the crosslinking temperature. The time of the mixing process at each stage is chosen so that good mixing of the components is achieved.

The tread rubber composition having a composition which can be prepared as described above surprisingly has the same level of abrasion resistance as the corresponding rubber composition containing only carbon black as a filler, Ta significantly lower than the corresponding rubber composition containing carbon black as an agent
n δ (dielectric loss factor). Low tan δ is associated with low rolling resistance. European Patent Publication No. 501227
As is clear from the publication, the rolling resistance is improved by substituting the carbon black with a known silica. As a result, the wear resistance was clearly reduced. However, in the rubber composition of the present invention, 30 to 100% by weight of the rubber component is composed of an isoprene-butadiene copolymer or an isoprene-butadiene-styrene copolymer, although the known silica is compounded. By doing so, deterioration of wear resistance can be avoided.

The tire tread of the present invention is composed of the rubber composition of the present invention. The tire of the present invention is a tire having a tread composed of the rubber composition of the present invention and a tread of this kind which can be vulcanized with sulfur. The rubber composition according to the present invention is used for producing a tire tread suitable for tires of passenger cars, two-wheeled vehicles, four-wheel drive vehicles, trucks and light trucks.

[0016]

The present invention will be described in detail with reference to the following examples. First, an example of a rubber composition containing an isoprene-butadiene copolymer as a specific rubber component will be described. Six types of rubber composition Nos. Having the composition shown in Table 1 1-6 were prepared. The blending composition in the table shows the blending amount of each component in parts by weight (hereinafter the same). Rubber composition No. 1 to 3 are compositions according to the examples of the present invention. Nos. 4 to 6 are compositions according to Comparative Examples that do not contain silica.

In Table 1, rubber component a is 80% by weight of butadiene and isoprene 2 synthesized by anionic polymerization.
It is an isoprene-butadiene copolymer of 0% by weight. The 1,2-bonds in the butadiene component are 52% by weight and the 3,4-bonds in the isoprene component are 36% by weight. The balance (%) in the butadiene component and the isoprene component is
It is a 1,4-bond.

The rubber component b is 80% by weight of butadiene and 20% by weight of isoprene synthesized by anionic polymerization.
Is an isoprene-butadiene copolymer. The 1,2-bond in the butadiene component is 38% by weight and the 3,4-bond in the isoprene component is 60% by weight. The balance (%) in the butadiene component and the isoprene component is 1,4-
It is a combination.

The rubber component c is an isoprene-butadiene copolymer of 75% by weight of anionically polymerized butadiene and 25% by weight of isoprene. The 1,2-bonds in the butadiene component are 40% by weight and the 3,4-bonds in the isoprene component are 60% by weight. The balance (%) in the butadiene component and the isoprene component is 1,4-bond.

As the silica VN3, Ultrasil VN3 (trade name), which is a commercial product of Degussa, is used, and the BET surface area is 170 m ² / g. Carbon black N234 has a BET surface area of 125 m ² / g (ISO
S-4652, ASTMD-3037, DIN661
32), CTAB surface area is 120 m ² / g
(Measured by ISO6810, ASTM D-3765), DBP oil absorption is 125 ml / 100 g (ISO6
810, measured according to ASTM D-2414, DIN 53601).

As a reinforcing material, carbon black N33 is used.
A mixture of 0 and polysulfide organosilane (mixing ratio 1: 1) was used. This mixture is commercially available as X 50-S (trade name) from Degussa. A diallyl-p-phenylenediamine mixture was used as an antioxidant. As the tackifier, a condensation product of p-tert-octylphenol and formaldehyde was used.

The vulcanization accelerator CBS is N-cyclohexyl-2-benzothiazolesulfenamide and the vulcanization accelerator DPG is N, N'-diphenylguanidine. Rubber composition No. 1-6 were prepared as follows.
That is, in the first stage, the rubber component was added to a kneader having a temperature of 50 ° C. and a rotation speed of 50 rpm and kneading. Then, zinc oxide, stearic acid, an antioxidant and a tackifier were added and kneaded. Then, the composition No. 1 to
In the case of 3, silica, a reinforcing material and an aromatic oil were added in an amount of ½ of the compounding amount and kneaded,
Composition No. In the cases of Nos. 4 to 6, carbon black and aromatic oil were added in an amount of ½ of the compounding amount and kneaded. Further, the remaining 1/2 amount of the above components was added and kneaded. Maximum temperature of 16 during all mixing operations
Hold at 0 ° C.

After cooling the mixture, it was kneaded again in the second stage. In this case, the temperature was also suppressed to 160 ° C. or lower. In the second stage, the rubber composition No. 1 to 3 only, not the composition using only carbon black. Further, in the third stage (the second stage in the case of Composition Nos. 4 to 6), a vulcanization system composed of sulfur and a vulcanization accelerator was mixed with a roll. Also in this case, the temperature was kept below the crosslinking temperature.

A vulcanized rubber test piece was prepared from each of the prepared rubber compositions, and the wear resistance and dielectric loss rate ta of each test piece were prepared.
nδ was evaluated. The dielectric loss rate (tan δ) was measured by 7
It was carried out at 0 ° C. and measured according to DIN 53513. The wear was measured according to DIN 53516. Rubber composition No. The measured value of 4 was defined as 100, and the measured values of other rubber compositions were expressed by indexes. When the index exceeds 100, it means that the property is improved. Rubber composition No. 1 to
The compounding composition of No. 6 and the measurement results are also shown in Table 1.

[0025]

[Table 1]

As can be seen from Table 1, the abrasion resistance of the rubber compositions (Nos. 1 to 3) according to the present invention is the same as those of the corresponding rubber compositions (No. 1 to No. 3) containing carbon black instead of silica.
It is almost equivalent to 4-6). This was unexpected. Because European Patent Publication No. 50122
According to the data of No. 7, it has been reported that when the rubber composition contains emulsion-polymerized SBR or solution-polymerized SBR, substitution of carbon black with silica results in a substantial decrease in abrasion resistance. Therefore, as shown in Table 1, the rubber composition according to the present invention has significantly improved tan δ related to rolling resistance, and further, does not have reduced abrasion resistance.

Next, a rubber composition using an isoprene-butadiene-styrene terpolymer as a specific rubber component will be described. As the terpolymer, two isoprene-butadiene-styrene terpolymers of d and e were used. The isoprene-butadiene-styrene terpolymers d and e each have a glass transition temperature of -90 ° C to
20 ° C., which are distinguished by a molecular structure based on the manipulations during the polymerization.

Rubber composition No. 1 having the composition shown in Table 2 containing the terpolymer d or e. 7-11 were prepared. Rubber composition No. Nos. 7 to 9 are rubber compositions according to the examples of the present invention. Nos. 10 and 11 are rubber compositions according to Comparative Examples that do not contain silica. Rubber composition No. 7-
11 was prepared as follows. That is, in the first stage, the rubber component was added to a kneader having a temperature of 50 ° C. and a rotation speed of 50 rpm and kneading. Then, zinc oxide, stearic acid, an antioxidant and a tackifier were added and kneaded. Then, the composition No. In case of 7 and 8,
The amount of silica, reinforcing material and aromatic oil is 1
/ 2 amount was added and kneaded to obtain a composition No. In case of 9,
Composition No. 1 was prepared by adding silica, carbon black, a reinforcing agent and aromatic oil in an amount of ½ of the compounding amount and kneading. In the case of Nos. 10 and 11, carbon black and aromatic oil were added in an amount of 1/2 of the compounding amount and kneaded. Further, the other half of the above components was added and kneaded. A maximum temperature of 160 ° C. was maintained during all mixing operations.

After cooling the mixture, it was kneaded again in the second stage. In this case, the temperature was also suppressed to 160 ° C. or lower. In the second stage, the rubber composition No. 7-9 only, not the composition using only carbon black. Furthermore, the third stage (Composition No. 10,
In the case of No. 11, in the second stage), a vulcanization system consisting of sulfur and a vulcanization accelerator was mixed with a roll. Also in this case, the temperature was kept below the crosslinking temperature.

The wear and the dielectric loss factor tan δ of the test piece prepared from the rubber mixture were determined according to the rubber composition No. 1-5
The rubber composition No. The measured value of 10 was defined as 100, and the measured values of other rubber compositions were represented by indexes. Rubber composition No. Table 2 shows the compounding compositions of 7 to 11 and the measurement results.

[0031]

[Table 2]

According to the data of European Patent Publication No. 501227, as long as the rubber composition contains emulsion-polymerized SBR or solution-polymerized SBR, substitution of carbon black with silica resulted in a substantial decrease in abrasion resistance. The abrasion resistance of the rubber composition (No. 7 to 9) according to the present invention is shown in Table 2.
As can be seen, it is almost equivalent to the corresponding rubber composition (No. 10, 11) containing carbon black instead of silica. That is, although the rubber composition according to the present invention has a significantly improved tan δ related to rolling resistance by substituting all or part of carbon black with silica, it has abrasion resistance due to the addition of silica. Is suppressed.

[0033]

INDUSTRIAL APPLICABILITY The rubber composition of the present invention has the same wear resistance as the rubber composition containing carbon black as a filler and has a rolling resistance in spite of containing silica as a filler. As lower than the rubber composition containing carbon black. Therefore, by using the rubber composition of the present invention, it is possible to obtain a tire tread having wear resistance and low rolling resistance (low fuel consumption), and thus a tire.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ulrich Steinbrecht Germany, 64372 Ober-Lamstatt Steinburgweg 15

Claims (15)

[Claims] 1. A rubber composition containing 20 to 90 parts by weight of silica with respect to 100 parts by weight of a rubber component, wherein at least 30% by weight or more of the rubber component is an isoprene-butadiene copolymer. And a rubber composition. 2. The rubber composition according to claim 1, wherein the isoprene-butadiene copolymer comprises 30 to 90% by weight of butadiene and the balance isoprene. 3. In the isoprene-butadiene copolymer, butadiene in the copolymer has a 1,2-bond component of 10 to 70% by weight, and isoprene has a 3,4-content of 20 to 70% by weight. The rubber composition according to claim 1 or 2, which has a binding component. 4. The rubber composition according to claim 1, wherein the glass transition temperature of the isoprene-butadiene copolymer is −90 ° C. to + 20 ° C. 5. The rubber component other than the isoprene-butadiene copolymer in 100 parts by weight of the rubber component is 0 to 50 parts by weight of natural rubber, and a conjugated diene-vinyl aromatic compound copolymer is synthesized by emulsion polymerization. The rubber composition according to any one of claims 1 to 4, wherein the rubber composition is 0 to 50 parts by weight of coalescence, 0 to 30 parts by weight of polybutadiene, or a combination thereof. 6. The conjugated diene-vinyl aromatic compound copolymer is an emulsion polymerization-styrene-butadiene copolymer having a glass transition temperature of −20 ° C. to −70 ° C. The rubber composition described. 7. A rubber composition containing 20 to 90 parts by weight of silica relative to 100 parts by weight of a rubber component, wherein at least 30% by weight of the rubber component has a glass transition temperature of −90 ° C. to 20 ° C. Isoprene-butadiene-
A rubber composition which is a styrene terpolymer. 8. The isoprene-butadiene-styrene terpolymer is composed of 5 to 30 wt% isoprene, 40 to 80 wt% butadiene, and 15 to 30 wt% styrene. Rubber composition. 9. The isoprene-butadiene-styrene terpolymer has 40 to 6 isoprene in the copolymer.
It has 0% by weight of 3,4-bond component and 20% of butadiene.
9. A rubber composition according to claim 7 or 8, characterized in that it has from 1 to 70% by weight of 1,2-bonding component. 10. A rubber component other than an isoprene-butadiene-styrene terpolymer out of 100 parts by weight of the rubber component, 0 to 50 parts by weight of natural rubber, and a conjugated diene-vinyl aroma synthesized by emulsion polymerization. Group compound copolymer 0
50 parts by weight, or 0 to 30 parts by weight of polybutadiene,
Or a combination thereof.
9. The rubber composition as described in any one of 9 above. 11. The method according to claim 10, wherein the conjugated diene-vinyl aromatic compound copolymer is an emulsion polymerization-styrene-butadiene copolymer having a glass transition temperature of −20 ° C. to −70 ° C. The rubber composition described. 12. The silica has a BET surface area of 100.
~ 250 m ² / g.
1. The rubber composition according to any one of 1. 13. The rubber composition according to claim 1, wherein the rubber composition contains carbon black as a filler, and the carbon black content is not more than the silica content. 14. A tire tread obtained by sulfur-vulcanizing the rubber composition according to claim 1. 15. A tire comprising the tire tread according to claim 14.