JP2890328B2 - Rubber composition for tire tread - Google Patents

Description

The present invention relates to a rubber composition for a tire tread having improved cut resistance, particularly a rubber for a tread of a large tire such as a construction vehicle, a truck, a bus, and a light truck. Composition.

Conventionally, as a compounding design of a rubber composition for a tire tread when cut resistance is particularly required, there is a tendency to increase hardness and elastic modulus, increase breaking elongation, and increase hysteresis loss. Styrene to component rubber
Butadiene copolymer rubber and various resins are blended. Further, in order to further improve the cut resistance, for example, as disclosed in JP-A-57-102933, a high styrene-containing styrene-butadiene copolymer having a styrene content of 30 to 70% by weight. It has been proposed to compound rubber. As described above, the rubber composition obtained by blending the styrene-butadiene copolymer rubber significantly increases the modulus of elasticity and hardness at room temperature, and significantly improves the cut resistance at room temperature. However, at a high temperature (60 ° C. or higher), the styrene-butadiene copolymer rubber has a large thermoplasticity, so that the rate of increase in elastic modulus and hardness is smaller than that at normal temperature, and the cut resistance is not sufficiently improved. There were drawbacks.

[Problems to be solved by the invention]

An object of the present invention is to provide a rubber composition for a tire tread having improved cut resistance over a wide temperature range from normal temperature to high temperature.

Here, the cut resistance refers to a property in which the tread portion is less likely to be cut by a stone or the like on the road when the tire runs.

[Means for solving the problem]

The rubber composition for a tire tread of the present invention comprises styrene-
A cresol-formaldehyde polycondensation resin, a phenol-formaldehyde polycondensation resin, based on 100 parts by weight of a raw rubber consisting of not less than 20 parts by weight of butadiene copolymer rubber and not more than 80 parts by weight of natural rubber and / or polyisoprene rubber
And at least one resin a selected from a resorcin-formaldehyde polycondensation resin and at least one resin b selected from a rosin-based resin and a petroleum-based resin, the total amount of b of a being 3 to 15 The blending ratio of parts by weight and a / b is 1/9 to 9/1, and the storage elastic modulus at 20 ° C. is 8.5 MPa or more and the storage elastic modulus at 100 ° C. is 4.0 MPa. It is characterized by the above.

 Hereinafter, the configuration of the present invention will be described in detail.

(1) Raw rubber.

It comprises at least 20 parts by weight of styrene-butadiene copolymer rubber (SBR) and at most 80 parts by weight of natural rubber (NR) and / or polyisoprene rubber (IR).

As described above, SBR and NR and / or IR are the reasons for the trade-off between cut resistance and heat generation due to external stress required for heavy-duty vehicles, in addition to securing the rubber strength required for heavy-duty tires. This is for balance of characteristics. If the SBR is less than 20 parts by weight, sufficient improvement in cut resistance is not observed.

(2) In the rubber composition of the present invention, the resin a and the resin b are mixed with 100 parts by weight of the raw rubber so that the total amount of the resins a and b is 3
1515 parts by weight and a / b in a ratio of 1/9 to 9/1. Further, other compounding agents such as carbon black may be compounded as needed.

The resin a is at least one selected from a cresol-formaldehyde polycondensation resin, a phenol-formaldehyde polycondensation resin, and a resorcin-formaldehyde polycondensation resin. The resin b is at least one selected from a rosin resin and a petroleum resin.
The rosin-based resin includes, for example, gum rosin WW, tall oil rosin, wood rosin, rosin-modified resin of the Haritac AQ series, and rosin derivatives such as maleated rosin.
The petroleum resin is, for example, an aliphatic petroleum resin such as Escolets 1102 or an aromatic petroleum resin such as petrozine.

If the total amount of a and b is less than 3 parts by weight, the effect of improving the cut resistance is not sufficient, while if it exceeds 15 parts by weight, the effect of improving the cut resistance is saturated, and the increase in heat generation is remarkable. Therefore, it is not preferable. In addition, when the mixing ratio of a / b is less than 1/9, the effect of improving cut resistance is small because the increase in elastic modulus and hardness is small.On the other hand, when the mixing ratio is more than 9/1, physical property changes due to aging become remarkable, which is not preferable. .

(3) The rubber composition of the present invention must have a storage modulus at 20 ° C of 8.5 or more and a storage modulus at 100 ° C of 4.0 PMa or more (storage at 20 ° C / 100 ° C). The elastic modulus is 8.5 / 4.0 or more respectively). 8.5 ° C storage elasticity at 20 ° C / 100 ° C
If the pressure is less than 4.0 MPa, the cut resistance in the temperature range from normal temperature to high temperature is insufficient.

 Examples and comparative examples are shown below.

Examples and Comparative Examples Table 1 shows the rubber compositions (Examples 1 and 2 and Comparative Examples 1 to 5).
Shows the blending content (parts by weight) and physical properties (index).

Examples 1 and 2 are within the scope of the present invention, and the storage elastic modulus is increased at both 20 ° C / 100 ° C, and the cut resistance is also improved.

Comparative Example 1 was a case where the ratio of styrene-butadiene copolymer rubber / natural rubber was 10 parts by weight / 90 parts by weight,
Although the storage elastic modulus of R.I. increases, the improvement in cut resistance is small due to the decrease in hysteresis loss.

Comparative Example 2 is a case where a blend of polybutadiene / natural rubber was used, and cut resistance was significantly reduced and taste was not good.

Comparative Example 3 is a case where the amount of the resin is less than 3 parts by weight, and the effect of improving the cut resistance is small.

Comparative Example 4 is a case where the resin compounding amount is more than 20 parts by weight,
Exothermicity becomes remarkable, which is not preferable.

Comparative Example 5 is blended within the range of the present invention, but has a storage elastic modulus of less than 8.5 / 4.0 MPa at 20 ° C./100° C., and does not exhibit cut resistance.

〔The invention's effect〕

As described above, according to the present invention, it is possible to improve cut resistance over a wide temperature range from room temperature to high temperature.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08L 93:04 57:02) (C08L 9/00 9:06 61:06 93:04 57:02) (56) References JP-A-56-47470 (JP, A) JP-A-61-225231 (JP, A) JP-A-60-99703 (JP, A) JP-A-59-204637 (JP, A) JP-A-58-120650 (JP, A) JP, A) JP-A-58-117235 (JP, A) JP-A-2-185543 (JP, A) JP-A-64-43544 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , (DB name) C08L 7/00-21/02

Claims (1)

(57) [Claims] 1. A cresol-formaldehyde polycondensation resin, a phenol-formaldehyde polycondensate, and a styrene-butadiene copolymer rubber (20 parts by weight or more) and a natural rubber and / or polyisoprene rubber (80 parts by weight or less) raw material 100 parts by weight Condensed resin, and at least one resin a selected from resorcin-formaldehyde polycondensation resin and at least one resin b selected from rosin-based resin and petroleum-based resin, the total amount of a and b 3 to 15 parts by weight and a / b
The compounding ratio of 1/9 to 9/1 is used for tire treads whose storage modulus at 20 ° C is 8.5MPa or more and whose storage modulus at 100 ° C is 4.0MPa or more. Rubber composition.