JP3494548B2 - Rubber composition for tire tread - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition containing carbon black, an aromatic oil and two or more diene rubbers. More specifically, the present invention relates to a rubber composition having a low glass transition temperature. A tire with a high balance of wet skid resistance and abrasion resistance, characterized by adding incompatible rubber with a high glass transition temperature and further blending a specific amount of specific carbon black and aroma oil. The present invention relates to a rubber composition for a tread.

[0002]

2. Description of the Related Art Conventionally, in order to obtain sufficient wet skid resistance, a rubber composition for a tire tread has been compounded with a large amount of carbon black and a plasticizer. It deteriorated, and the plasticizer volatilized, so that deterioration with time was also large. On the other hand, a technique of blending a rubber excellent in wet skid resistance in order to improve wet skid resistance is also known, but a rubber excellent in wet skid resistance generally has a problem of poor abrasion resistance.

Therefore, it has not been possible to obtain a rubber composition for a tire tread in which the wet skid resistance and the wear resistance are highly balanced (that is, both are improved).

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to improve wet skid resistance and abrasion resistance by containing two or more kinds of rubbers which are incompatible with each other, a specific carbon black, and an aromatic oil. It is to provide a highly balanced rubber composition for a tire tread.

[0005]

A rubber composition for a tire tread according to the present invention comprises a diene rubber having a glass transition temperature of −35 ° C. to 0 ° C. with respect to 80 to 20 parts by weight of a diene rubber having a glass transition temperature of −50 ° C. or less. 20 to 80 parts by weight of rubber is added, and N ₂ SA
24M4DBP at 65 ~ 200m ² / g is composed of 90 ~ 150ml / 100g of carbon black and aroma oil, and the interaction parameter (χ _eff ) between the compounded rubbers and the spinodal point of the rubber blend system. The difference (χ _eff −χ _s ) from the action parameter (χ _s ) is set within the range of 2.0 × 10 ^{−4 to} 1.2 × 10 ⁻² , and the carbon black and the aromatic oil are represented by the following formula (a). The value of φ defined by is 0.48 ≦ φ ≦
It is characterized by being blended in an amount of 0.70.

[0006] Here, C: carbon black compounding amount (parts by weight) ρ: specific gravity of rubber S: oil compounding amount (parts by weight) As described above, a rubber composition containing two or more diene rubbers having different glass transition temperatures (Tg). Difference (χ _eff ) between the interaction parameter (χ _eff ) at the temperature during rubber vulcanization and the spinodal point interaction parameter (χ _s )
-Χ _s ) makes it possible to make the blended rubbers incompatible with each other, and because of the blending of specific carbon black and aroma-based oil, wet skid resistance and abrasion resistance The sex can be highly balanced.

Here, χ _eff is Macromolecules, 24,
It is calculated by the following formula shown in 4844 (1991). χ _eff = χ _{1 −} χ ₂ ······· χ _s is calculated by the following general equation of thermodynamics. 2 χ _s = 1 / N ₁ φ ₁ + 1 / N ₂ φ ₂ ... N ₁ : 1 component polymerization degree, N ₂ : 2 component polymerization degree, φ ₁ :
Molar fraction of one component φ ₂ : Molar fraction of two components

[0008] χ _eff <χ _s: compatible, χ _eff> χ _s: incompatible _{χ 1 = aeχ SV + afχ SB} + bdχ SV + bfχ VB + cd
_{χ SB + ceχ VB χ 2 =} abχ SV + acχ SB + bcχ VB + deχ SV + df
χ _SB + ef χ _VB χ _SV = 56.5 × 10 ^-3 ＋ 5.62 / T χ _SB ＝ 8.43 × 10 ^-3 ＋ 10.2 / T χ _VB ＝ 2.69 × 10 ^-3 + 1.87 / T

Styrene amount Vinyl amount Butadiene amount One diene rubber a b c The other diene rubber d ef χ _SV : Interaction parameter χ _{SB of} styrene unit and 1,2-bond butadiene unit χ _SB : Styrene unit and 1, Interaction parameter of 4-bond butadiene unit χ _VB : Interaction parameter of 1,2-bond butadiene unit and 1,4-bond butadiene unit χ _eff : Interaction parameter of polymer χ ₁ : Interaction parameter of polymer molecule χ ₂ : Interaction parameter in polymer molecule χ _s : Interaction parameter at spinodal point of polymer blend system T: Absolute temperature at rubber vulcanization (° K)

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a glass transition temperature of -50
20 to 80 parts by weight of a diene rubber having a glass transition temperature of -35 ° C to 0 ° C is mixed with 80 to 20 parts by weight of a diene rubber having a temperature of ℃ or less.
A diene rubber having a glass transition temperature of −50 ° C. or lower is excellent in wear resistance and low temperature performance. The glass transition temperature is -35.
Diene rubber in the range of ℃ ~ 0 ℃, t
Has a peak of anδ and has excellent wet skid resistance. If the two are not compatible with each other, the properties of the both are expressed and a sufficient effect can be expected. It is not preferable to add more than 80 parts by weight of a rubber having a high glass transition temperature (diene rubber having a Tg of −35 ° C. to 0 ° C.) because the abrasion resistance is greatly deteriorated. Also,
Even if it is less than 20 parts by weight, the effect of compounding a rubber having a high glass transition temperature can be seen, but it is insufficient to compensate for the wet skid resistance which is decreased due to the reduction of carbon black / oil. A rubber blend having a value of χ _eff -χ _s of less than 2.0 × 10 ^-4 is nearly compatible, and the effect of compounding a high glass transition temperature rubber is not sufficiently exhibited. On the other hand, if the value of χ _eff -χ _s exceeds 1.2 to 10 ^-2 , the domain size of the dispersed phase becomes too large and the tensile strength and wear resistance deteriorate, which is not preferable.
It is preferably 5.0 × 10 ^{−4 to} 5.0 × 10 ⁻³ .

Examples of the diene rubber having a glass transition temperature of -50 ° C or less include polybutadiene rubber (BR) and styrene-
Butadiene copolymer rubber (SBR), polyisoprene rubber (IR), natural rubber (NR), or a mixture thereof are preferable, but not limited thereto. The diene rubber having a glass transition temperature of −35 ° C. to 0 ° C. is, for example, polybutadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), polyisoprene rubber (IR), or a mixture thereof. Preferred examples include, but are not limited to.

Further, in the present invention, N ₂ SA is 65 to 200 m.
Carbon black 24M4DBP is 90 ~ 150 mL / 100 g in ² / g, and aromatic type oil, is defined by the following formula (a) phi
The value is 0.48 ≦ φ ≦ 0.70, preferably 0.50 ≦ φ ≦ 0.67. Here, C: compounded amount of carbon black (parts by weight) ρ: specific gravity of rubber S: compounded amount of oil (parts by weight)

The value of φ also changes when the blending amounts of carbon black and aroma oil are changed. Also, the wear resistance changes with φ, and when the value of φ is φ = 0.5,
It was found that the wear resistance was maximized. φ value is 0.4 ~
If it is between 0.7, there is an effect of improving wear resistance, but φ is
When it is less than 0.48, the wet skid resistance is largely lowered, and the wet skid resistance and the wear resistance cannot be highly balanced.

[0014]

[Examples] Four kinds of polymers shown in Table 1 were compounded by the compounding method (parts by weight) shown in Table 2 and vulcanized at 160 ° C for 30 minutes to obtain rubber compositions (Examples 1 to 6). Comparative Examples 1 to
7). Polymers A to E are commercially available products, A: NIPOL 171
2, B: NIPOL 9528, C: NS 116, D: NIPOL 9529,
E: NIPOL 1220, both manufactured by Nippon Zeon Co., Ltd.

The styrene content and vinyl content of each of the polymers A to E were measured by a conventional infrared spectroscopic method (styrene content: Hampton method, vinyl content: Morero method). Molecular weight (Mw)
Is gel permeation chromatography (GPC)
Was measured using. The glass transition temperature (Tg) was measured using a differential scanning calorimeter (DSC) at a heating rate of 10 ° C / min.

[0016]

[Table 1]

[0017]

[Table 2]

Table 3 shows the calculated values of χ _eff -χ _s of Examples 1 to 6 and Comparative Examples 1 to 7, which are outside the scope of the present invention, and Example 1.
.About.6 and the tan .delta. (0.degree. C.) and abrasion resistance values of the vulcanizates of Comparative Examples 1 to 7 are shown. tanδ is frequency 20Hz
, Initial strain 10%, amplitude ± 2%. The value of tan δ (0 ° C) at this time correlates with wet skid resistance. The larger the number, the better the wet skid resistance.

The abrasion resistance was measured by using a Lambourn abrasion tester according to the test method specified in JIS K6301. It is shown by an index with Comparative Example 1 being 100. The larger the number, the better the abrasion resistance.

[0020]

[Table 3]

From the comparison between Comparative Examples 1 and 5 and Comparative Examples 2 and 4, when the value of φ is within the range of the present invention, the wear resistance is improved, but the wet skid resistance is deteriorated. Recognize. Even if other polymers are blended as in Comparative Example 3, wet skid resistance is not sufficiently improved if the value of χ _eff -χ _s is outside the range of the present invention. From the comparison between Example 5 and Comparative Example 6, the value of φ and χ
_{Even if} the value of _{eff −} χ _s is within the range of the present invention, if the carbon black outside the range of the present invention is used, the wear resistance is significantly reduced. Furthermore, from the comparison between Example 6 and Comparative Example 7,
Even if the value of φ and the value of χ _{ef f} −χ _s are within the range of the present invention, if the Tg of the polymer is outside the range of the present invention, the wet skid resistance is significantly reduced.

As in Examples 1 to 6, φ within the scope of the present invention
By blending the polymer within the range of the present invention, it is possible to greatly improve the wear resistance while maintaining the wet skid resistance at a high level.

[0023]

As described above, according to the present invention, two or more diene rubbers having different Tg's, fillers, and
In the rubber composition containing the extender oil for rubber, the interaction parameter (χ _eff ) between the blended rubbers and the interaction parameter (χ _s ) of the spinodal point of the rubber blend system
The difference (χ _eff −χ _s ) is within the range of 2.0 × 10 ^-4 × to 1.2 × 10 ^-2 , and since the specific carbon black and the aromatic oil are blended, the wet skid resistance and The wear resistance can be highly balanced.

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) C08L 9/00-9/10

Claims (3)

(57) [Claims] 1. A diene-based resin having a glass transition temperature of −50 ° C. or lower.
Glass with a glass transition temperature of −35 ° C. to 0 ° C. for 80 to 20 parts by weight.
Add 20 to 80 parts by weight of ene rubber and add N ₂SA is 65
~ 200 m²24M4DBP is 90 ~ 150ml / 100g of carbon per gram
A rubber blended with black and aromatic oils.
Interaction parameter (χ_eff) And its rubber blend
Interaction parameter (χ_s)When
Difference of (χ_eff−χ_s) 2.0 × 10^-Four~ 1.2 x 10^-2Range of
Inside, and with the carbon black and the aroma oil
And the value of φ defined by the following equation (a) is 0.48 ≦ φ ≦
A rubber composition for a tire tread compounded in an amount of 0.70. Here, C: compounding amount of carbon black (parts by weight) ρ: Specific gravity of rubber S: Oil blending amount (parts by weight) 2. The diene rubber having a glass transition temperature of −50 ° C. or lower is polybutadiene rubber, styrene-butadiene copolymer rubber, polyisoprene rubber, natural rubber, or a mixture of one or more thereof. Rubber composition for tire tread. 3. The diene rubber having a glass transition temperature of −35 ° C. to 0 ° C. is polybutadiene rubber, styrene-butadiene copolymer rubber, polyisoprene rubber, or a mixture of one or more thereof. Rubber composition for tire tread of.