JP4622512B2 - Rubber composition - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a rubber composition, and more specifically, a rubber composition having two or more specific types of silica having different particle diameters, excellent workability and dispersibility, and excellent mechanical properties and wear resistance. Related to things.

Currently, silica is used as a filler for tire reinforcement, and the amount of use is increasing year by year. In general, silica has a problem that the interaction between silica and silica is stronger than the interaction between rubber and silica due to the influence of silanol groups on the surface of the silica, and the silica is not uniformly dispersed in the rubber. Conventionally, when silica with a large N ₂ SA value is blended with rubber, processing / dispersibility is poor, and when silica with a small N ₂ SA value is blended with rubber, processing / dispersibility is good, but tensile properties and wear resistance are low. It is known that there is a problem of getting worse. Therefore, there is a strong demand for a method for obtaining a silica-containing rubber composition that has good processing and dispersibility, and that is excellent in mechanical properties and wear resistance.

In Patent Document 1 below, in order to improve the above problem, a specific amount of two specific types of silica having different maximum pore size distribution and different N ₂ SA are blended with the olefinic unsaturated elastomer. Discloses a prior art which has obtained a rubber composition having good rolling resistance and wet grip, and good tensile strength and handleability. However, further improvements are desired to obtain better desired properties.

JP 2001-89605 A

  Therefore, in the present invention, by blending two or more kinds of specific silicas having different particle diameters, a rubber composition having even better processability and dispersibility, and excellent mechanical properties and wear resistance is obtained. The purpose is to provide.

According to the present invention, 100 parts by weight of rubber to, N ₂ SA N ₂ SA of (nitrogen adsorption specific surface area) is different from the silica A of the largest N ₂ SA value and silica B of the smallest N ₂ SA value Two or more types of silica having a difference in value of 30 or more are included so that the blending ratio α (silica A / silica B) satisfies 0.5 <α ≦ 10, and the N ₂ SA is different. Two or more types of silica are two or more types of silica, a silica having a mesh residue of 2000% or less and a silica having a mesh size of 2000m or less and a residue of a mesh of 2000m or more and a silica content of 50% or more. And a rubber composition comprising 0.1 to 15% by weight of a silane coupling agent based on the total amount of silica.

  Furthermore, a pneumatic tire using the rubber composition is provided.

In the present invention, such as the difference between the N ₂ SA value of the N ₂ SA is different two or more kinds of silica and silica of the most significant N ₂ SA value and its most small N ₂ SA value silica is 30 or more, Combining two or more specific types of silica with different silica particle sizes into rubber solves the problems related to conventional processability and dispersibility in silica compounded rubber compositions as well as the problems of reduced mechanical properties and wear resistance. And it has been found that better results can be obtained.

As the two or more types of silica having different particle diameters used in the present invention, general silica powders conventionally used for rubber fillers are used, and two or more types of silica having different particle sizes are selected. Need only be blended into the rubber together with other compounding agents. In the present invention, “N ₂ SA (nitrogen adsorption specific surface area)” and “aperture 2000 μm sieve” are used as an index and standard indicating the difference in particle diameter of the silica.

The rubber composition of the present invention, in order to achieve the intended purpose, at least N ₂ SA is different The major N ₂ SA value silica and the N ₂ SA of the silica of the smallest N ₂ SA value It is preferable to use two or more kinds of specific silicas having a difference of 30 or more, preferably 30 to 200, more preferably 40 to 140. The reinforcing filler containing two or more specific types of silica needs to be used in an amount of 30 to 150 parts by weight. The total amount of the reinforcing filler may be two or more kinds of silicas having different N ₂ SA, and another reinforcing filler such as carbon black may be blended in a part thereof. In this case, among the reinforcing fillers, the total amount of two or more kinds of silicas having different N ₂ SA is preferably 30 to 120 parts by weight, more preferably 40 to 100 parts by weight. If the blending amount of two or more kinds of silicas with different N ₂ SA is less than 30 parts by weight, the desired effect cannot be achieved. Conversely, if it exceeds 120 parts by weight, processability and dispersibility deteriorate. It is not preferable.

Further, as the two or more kinds of silicas having different N ₂ SA blended in the rubber composition of the present invention, the residue of the 2000 μm sieve mesh is 5% or less and the residue of the 2000 μm sieve sieve is 50%. It is more preferable to use two or more types of silica with the above silica.

Furthermore, at least two or more kinds of silica the N ₂ SA is different for use in the present invention, the most significant N ₂ SA compounding ratio of silica A and silica B of the smallest N ₂ SA value of value alpha (Silica A / Silica B) is preferably 0.5 <α ≦ 10, more preferably 1.3 <α ≦ 8. When the blending ratio α is 0.5 or less, the desired effect cannot be exhibited. On the other hand, when it exceeds 10, only the characteristics of silica A (silica having a large N ₂ SA) are manifested. Absent.

In the rubber composition of the present invention, 0.1 to 15% by weight, preferably 3 to 12% by weight, of a silane coupling agent is further blended with respect to the total amount of at least two kinds of silicas having different N ₂ SA. . If the amount of the silane coupling agent is less than 0.1% by weight based on the total amount of silica, the desired effect is not achieved, and if it exceeds 15% by weight, the compound is liable to cause a crosslinking reaction during mixing. Therefore, it is not preferable.

  As the rubber component in the rubber composition of the present invention, commonly used diene rubbers and other rubbers can be used effectively. Commonly used diene rubbers include, for example, natural rubber (NR), polyisoprene rubber (IR), various butadiene rubbers (BR), various styrene-butadiene copolymer rubbers (SBR), and acrylonitrile-butadiene copolymer rubbers. (NBR), chloroprene rubber, ethylene-propylene-diene copolymer rubber, styrene-isoprene copolymer rubber, styrene-isoprene-butadiene copolymer rubber, isoprene-butadiene copolymer rubber and the like.

  The rubber composition of the present invention is further blended with ordinary vulcanization or crosslinking agents, vulcanization or crosslinking accelerators, various oils, anti-aging agents, fillers, plasticizers, and other tire rubbers or general rubbers. Various compounding agents can be blended, and these compounding agents can be kneaded and vulcanized 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.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further, it cannot be overemphasized that the scope of the present invention is not limited to these Examples.

Preparation of test samples Vulcanization accelerators and ingredients other than sulfur in the formulations shown in Table 1 below were kneaded for 5 minutes in a 1.8 L closed mixer, and vulcanization was accelerated to the master batch released when the temperature reached 160 ° C. The rubber composition was obtained by kneading the agent and sulfur with an 8-inch open roll. This unvulcanized rubber composition was subjected to a Mooney scorch test. Next, this rubber composition was press vulcanized at 160 ° C. for 20 minutes in a 15 cm × 15 cm × 0.2 cm mold and a disk-shaped mold having a diameter of 49 mm and a thickness of 5 mm to obtain a target test piece (rubber sheet And subjected to the following breaking strength test and wear resistance test.

Test method 1) Mooney scorch test: Based on JIS K 6300, the time (minute) during which the Mooney viscosity increased by 5 points at 125 ° C. was measured. The larger the index, the longer the scorch time.
2) Breaking strength test: In accordance with JIS K6251, a sheet was punched out with a No. 3 dumbbell, a tensile test was performed at a tensile speed of 500 mm / min, and the breaking strength was measured. did. The larger the index, the higher the breaking strength.
3) Abrasion resistance test: Using a Lambourn abrasion tester (manufactured by Iwamoto Seisakusho), the load was 1.5 kg, the slip rate was 50%, the time was 10 minutes, and the room temperature was measured. Expressed as an index of 100. The larger the index, the better the wear resistance.

Examples 1-5 and Comparative Examples 1-2
The results are shown in Table 1.

  According to the results of Table 1, according to the present invention, the processability and dispersibility are excellent, and the mechanical properties and the wear resistance are excellent, which are not obtained in the prior art and are not found in the prior art. It can be seen that a rubber composition is obtained.

  The rubber composition according to the present invention can generally be used as a tire, a conveyor belt, a seismic isolation rubber or a hose material, and is particularly effective when used for a pneumatic tire.

Claims (2)

100 parts by weight of the rubber to, N ₂ SA (nitrogen adsorption specific surface area) is different from its most difference N ₂ SA value of silica B silica A large N ₂ SA value with its smallest N ₂ SA value is 30 or more And two or more types of silicas having different N ₂ SA are included so that the blending ratio α (silica A / silica B) is 0.5 <α ≦ 10. , mesh residue of 2000μm sieve residue of less than 5% of silica and mesh 2000μm sieve is two or more silica with 50% or more of silica, silica amount 30 to 120 parts by weight, and the silica amount A rubber composition comprising 0.1 to 15% by weight of a silane coupling agent based on the weight of the rubber composition.   A pneumatic tire using the rubber composition according to claim 1.