JP4180093B2 - Rubber composition - Google Patents

Description

  The present invention relates to a rubber composition, and more specifically, a rubber having a predetermined amount of dry-heat treated silk powder, excellent filler dispersibility, excellent elastic modulus at high temperature, and excellent wear resistance. Relates to the composition.

  Conventionally, in the rubber industry, means for reinforcing rubber by blending carbon black as a reinforcing filler has been employed, but there has been a problem that the heat generated by rubber is high and the rolling resistance is large. Therefore, in recent years, the above problem has been solved by blending silica as a filler instead of carbon black. However, it is known that the silica is easily agglomerated with each other due to the characteristics of the silica surface, so that the mixing property is deteriorated. Therefore, in general, as shown in the following Patent Document 1, the dispersibility of silica has been increased by using a silane coupling agent in combination, but this is a novel method for further improving the physical properties of rubber. Search for fillers is required.

  In Patent Document 2 below, a predetermined amount of silk powder with a predetermined particle size is blended with a resin or rubber to obtain a molded product having high production efficiency and moisture permeability, moisture absorption / release properties and appearance comparable to natural products. Patent Document 3 below discloses that a transmission belt with improved durability can be obtained by blending a predetermined amount of silk short fibers into the adhesive rubber layer of the transmission belt. Has been. However, no technology has been proposed for blending silk powder in order to improve the mixing and processability of the silica-containing rubber composition and improve the physical properties.

JP 7-48476 A Japanese Patent No. 2832010 JP-A-9-144815

In the present invention, by adding a predetermined dry heat-treated silk powder to the silica-blended rubber composition, the rubber composition is excellent in filler dispersibility, excellent in elastic modulus at high temperature, and in wear resistance. Another object of the present invention is to provide an excellent rubber composition.

According to the present invention, with respect to 100 parts by weight of the diene rubber, dry heat-treated silk powder 0.1 to 0.1 obtained by heat-treating the silk raw material for 30 to 480 minutes at a temperature of 180 to 300 ° C. in a closed dryer. There is provided a rubber composition comprising 30 parts by weight, 40 to 100 parts by weight of a reinforcing filler containing silica, and 3 to 20% by weight of a silane coupling agent based on silica.

In the silica compounded rubber composition, the present inventors blended a predetermined amount of the dry heat-treated silk powder together with a conventional silane coupling agent, so that the dispersibility of the silica filler is excellent, and the elastic modulus at high temperature is excellent. It has also been found that a rubber composition excellent in wear resistance can be obtained.

  Examples of the diene rubber used in the rubber composition of the present invention include natural rubber (NR), various butadiene rubbers (BR), various styrene-butadiene copolymer rubbers (SBR), polyisoprene rubber (IR), acrylonitrile. -Butadiene copolymer rubber (NBR), chloroprene rubber, ethylene-propylene-diene copolymer rubber, styrene-isoprene copolymer rubber, styrene-isoprene-butadiene copolymer rubber, isoprene-butadiene copolymer rubber, etc. Can be mentioned. The diene rubber may be modified with an epoxy group, an alkoxysilane group, a hydroxyl group-containing group, or the like. These diene rubbers may be used alone or as a blend rubber of two or more.

As the dry heat-treated silk powder used in the rubber composition of the present invention, for example, a 250 mesh sieve based on the Tyler sieve standard is used, and the maximum particle size is less than 63 μm, preferably 50 μm or less, more preferably 35 μm or less. Are effectively used. As the dry heat-treated silk powder , the smaller the particle size, the better the reinforcing performance.

The dry heat-treated silk powder can be embrittled by, for example, placing 200 g each in a hot air dryer and arranging silk raw materials in a total of 6 stages and drying with hot air at 210 ° C. for 60 minutes. The pulverization can be made into powder by pulverizing for 3 hours by a ball mill pulverization method. If the temperature condition in the dry heat treatment is 180 ° C. or less, it is not preferable in terms of time efficiency, and if the temperature condition exceeds 300 ° C., there is a high possibility that the silk will burn. Therefore, it is preferable that the said temperature conditions are 180-300 degreeC, More preferably, it is 200-220 degreeC.

The dry heat-treated silk powder used in the rubber composition of the present invention is 0.1 to 30 parts by weight, more preferably 1 to 15 parts per 100 parts by weight of the diene rubber together with a predetermined amount of silane coupling agent. Formulated in an amount of% by weight. If the amount is less than 0.1 parts by weight, the desired effect is not obtained. Conversely, if it exceeds 30 parts by weight, the wear resistance of the rubber composition is remarkably deteriorated, which is not preferable.

  The amount of silica used in the rubber composition of the present invention is 10 to 100 parts by weight, more preferably 40 to 80 parts by weight, based on 100 parts by weight of the diene rubber. If the amount of silica is less than 10 parts by weight, the silica-specific effects cannot be obtained, which is not preferable. On the other hand, if it exceeds 100 parts by weight, the mixing / workability of the rubber composition is deteriorated and the hardness is high. It is not preferable because it becomes too difficult to mold.

  In the rubber composition of the present invention, carbon black may be used in combination as a reinforcing filler other than silica, but the amount of such carbon black is based on 100 parts by weight of the diene rubber, The amount can be blended in an amount of 90 parts by weight or less and the total amount of the reinforcing filler containing silica is 40 to 100 parts by weight. However, if the blending amount exceeds 50 parts by weight, the heat generation of the rubber composition is increased and rolling resistance is increased, which is not preferable.

  Furthermore, the rubber composition of the present invention contains 3 to 20% by weight, preferably 5 to 12 parts by weight of a silane coupling agent, based on the compounded silica. It is preferable to blend such a predetermined amount of the silane coupling agent because the reaction efficiency between the silica-coupling agent-rubber is good and the rubber reinforcing property is excellent. As the silane coupling agent, a sulfur-containing silane coupling agent is preferably used. For example, 3,3′-bis (trimethoxy or triethoxysilylpropyl) disulfide is particularly preferable, and 3,3′-bis (triethoxy Silylpropyl) tetrasulfide is most preferred.

  The rubber composition according to the present invention further includes a vulcanization or crosslinking agent, a vulcanization or crosslinking accelerator, various waxes, oils, anti-aging agents, fillers, plasticizers and other tires, and other rubber compositions. Various compounding agents blended in the above can be blended, and these blending agents can be kneaded 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 this invention is further demonstrated by an Example and a comparative example, it cannot be overemphasized that the technical scope of this invention is not limited to these Examples.

Preparation of Test Sample According to the formulation (parts by weight) shown in Table 1, each compounding component such as rubber, silica, and dry heat treated silk powder excluding sulfur and vulcanization accelerator was loaded into a 1.7 L closed Banbury mixer. The master batch which was mixed for a minute and then released to the outside of the mixer and cooled to room temperature was put into the Banbury mixer again, and sulfur and a vulcanization accelerator were blended and mixed to obtain a rubber composition. . Next, this rubber composition was press vulcanized at 160 ° C. for 20 minutes in a 15 cm × 15 cm × 0.2 cm mold to produce a test sample (rubber sheet), and the following E ′ (storage modulus) and It was subjected to an abrasion resistance test.

Test Method 1) E ′ (tan δ (60 ° C.)): According to JIS K6394, using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho, static strain = 10%, dynamic strain = ± 2 %, Frequency = 20 Hz, E ′ (tan δ (60 ° C.)) was measured. The results are shown as an index with Comparative Example 1 as 100. The larger the index, the higher the elastic modulus at high temperature, which is superior.
2) Abrasion resistance: 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. As an index. It shows that abrasion resistance is excellent, so that an index | exponent is large.

Examples 1-6 and Comparative Examples 1-2
The results are shown in Table 1 below.

From the results of Table 1, in Examples 1 to 6 in which a dry blended silk powder of a predetermined blending amount was blended with a silica blended rubber composition, a rubber composition excellent in elastic modulus at high temperature and excellent in wear resistance. You can see that things are being obtained.

  Therefore, the rubber composition of the present invention is extremely useful particularly when used as a cap tread portion of a tire for a pneumatic tire.

Claims (3)

For 100 parts by weight of diene rubber, 0.1 to 30 parts by weight of dry heat-treated silk powder obtained by heat-treating silk raw material for 30 to 480 minutes at 180 to 300 ° C. in a hermetic dryer , silica A rubber composition comprising 40 to 100 parts by weight of a reinforcing filler and 3 to 20% by weight of a silane coupling agent based on silica. The rubber composition according to claim 1, wherein the dry heat-treated silk powder has a particle size of 50 μm or less. A pneumatic tire using the rubber composition according to claim 1 for a cap tread.