JP2007231104A - Rubber composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition that makes it possible for the formulation amount of zinc oxide in the rubber composition to be lessened without deteriorating the physical properties of the rubber composition. <P>SOLUTION: The rubber composition comprises (i) at least one diene rubber, (ii) carbon black and/or silica, (iii) sulfur, and (iv) zinc oxide with an average particle size of <80 nm as a vulcanization promoting assistant. As the diene rubber preferably used are SBR, NR, IR, BR, IIR, CR, NBR, EPDM and the like. The rubber composition exhibits suitable properties for the use in pneumatic tires. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a rubber composition, and more particularly to a rubber composition in which the compounding amount of zinc oxide is reduced without substantially affecting rubber physical properties.

  Attempts have been made to reduce the amount of zinc oxide used in rubber compositions. For example, zinc oxide fine particles having a particle size of 200 nm or less are uniformly dispersed in carbon black particles with respect to 100 parts by weight of one or more rubber components selected from natural rubber, diene rubber or chloroprene rubber, nitrile rubber, and ethylene propylene rubber. A rubber composition comprising 20 to 200 parts by weight of zinc oxide composite carbon black is known (see Patent Document 1). According to this method, strength and wear resistance can be achieved even with a small amount of zinc oxide used. It is described that an excellent rubber composition can be obtained.

JP-A-5-222245

  Accordingly, an object of the present invention is to significantly reduce the amount of zinc oxide in the rubber composition without substantially reducing the physical properties, particularly mechanical strength and viscoelastic properties of the rubber composition.

  According to the present invention, there is provided a rubber composition comprising diene rubber, carbon black and / or silica, sulfur and zinc oxide having an average particle size of less than 80 nm as a vulcanization acceleration aid.

  According to the present invention, by using zinc oxide having an average particle size of 80 nm or less in the rubber composition, the physical properties of the rubber composition, particularly mechanical properties and viscoelastic properties are not deteriorated. The amount of zinc used can be reduced to a maximum of 1/10.

As a result of researches to solve the above problems, the present inventors have determined that the average particle diameter measured by the aeration method is less than 80 nm, preferably 50 to 20 nm, and the nitrogen adsorption method (BET method) (JIS-K6217-). 2 (for carbon black)) zinc oxide having a specific surface area of 10 m ² / g or more (more preferably 100 to 200 m ² / g) (average particle size of conventional general-purpose zinc oxide is 0.25 to 0. 0). By using 6 μm and a specific surface area of 4 to 7 m ² / g), it was found that substantially the same physical properties can be expressed even if the amount of zinc used is reduced to 1/10 of the conventional amount.

  In a preferred embodiment of the present invention, zinc oxide having an average particle size of less than 80 nm as a vulcanization accelerating aid and carbon black and / or silica 20 to 150 parts by weight, sulfur 1 to 5 parts by weight and 100 parts by weight of diene rubber. 0.01-5 weight part is mix | blended.

  The diene rubber compounded in the rubber composition of the present invention may be any diene rubber that can be generally compounded in various rubber compositions such as natural rubber (NR), polyisoprene rubber (IR), various styrene-butadienes. Copolymer rubber (SBR), various polybutadiene rubbers (BR), acrylonitrile-butadiene copolymer rubber (NBR), butyl rubber (IIR) and the like can be used alone or as any blend.

  The carbon black and / or silica used in the present invention is preferably blended in an amount of 20 to 150 parts by weight, more preferably 50 to 150 parts by weight, based on 100 parts by weight of the diene rubber. If the blending amount is too small, the reinforcing effect is too low and the mechanical properties may not be satisfied. If the blending amount is too large, poor dispersion, increased hardness, and reduced elongation may occur. Carbon black and silica that can be used are not particularly limited, and the ratio of carbon black and silica is not particularly limited.

  As the sulfur used in the present invention, any sulfur used for blending in the rubber composition can be used, and the blending amount thereof is not particularly limited, but is preferably based on 100 parts by weight of the diene rubber. Is 1 to 5 parts by weight, more preferably 1 to 3 parts by weight. If the blending amount is small, the crosslinking density is too low and the mechanical properties may be too low. If the blending amount is too large, the crosslinking density is too high and the elongation may decrease and the hardness may increase.

As described above, the zinc oxide used as a vulcanization accelerator auxiliary in the present invention has an average particle size of less than 80 nm, preferably an average particle size of 50 to 20 nm, and a specific surface area of 10 m ² / g or more (more preferably 100-200 m ² / g) is used. If the average particle size of the zinc oxide used is large, the number of reaction sites on the surface decreases, which is not preferable. Moreover, it is not preferable for the same reason that the specific surface area of the particles is small.

  Zinc oxide having an average particle size of less than 80 nm used in the present invention can be produced, for example, by a method called a gas phase method. The vapor phase method (PVS method) is an ultrafine particle manufacturing technology developed by the US Nanophase Technology Company. The raw material (metal zinc) becomes vapor of metal atoms by thermal energy, and comes into contact with the reaction gas (oxygen). Metal oxide molecules (that is, zinc oxide) and clusters are formed, and then cooled instantaneously, thereby suppressing an increase in particle size and obtaining zinc oxide of less than 80 nm.

  In addition to the components described above, the rubber composition according to the present invention is used for tires such as vulcanization or crosslinking agents, vulcanization or crosslinking accelerators, various oils, anti-aging agents, plasticizers, and other rubber compositions. Various additives that are generally blended in the above can be blended, and such additives can be kneaded by a general method to form a composition, which can be used for vulcanization or crosslinking. As long as the amount of these additives is not contrary to the object of the present invention, a conventional general amount can be used.

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

Examples 1-2 and Comparative Examples 1-4
Sample preparation In the formulation shown in Table I, the components excluding the vulcanization accelerator and sulfur were kneaded for 5 minutes in a 1.6 liter closed mixer and released when the temperature reached 150 ° C to obtain a master batch. A vulcanization accelerator and sulfur were kneaded with this masterbatch with an open roll to obtain a rubber composition. Using this rubber composition, unvulcanized physical properties were evaluated by the following test methods. The results are shown in Table I.

  Next, the obtained rubber composition was vulcanized in a 15 × 15 × 0.2 cm mold at 160 ° C. for 15 minutes to prepare a vulcanized rubber sheet, and the physical properties of the vulcanized rubber were measured by the following test methods. It was measured. The results are shown in Table I.

Rubber physical property evaluation test method JIS-A hardness: Measured according to JIS K6253.
300% modulus (M300) and 100% modulus (M100): Measured according to JIS K6251.
Breaking strength (TB) and breaking elongation (EB): Measured according to JIS K6251.

  tan δ (0 ° C. and 60 ° C.): Measured at a temperature of 0 ° C. and 60 ° C. using an extension-type viscoelasticity measuring device (manufactured by Toyo Seiki Co., Ltd.) with an initial elongation of 10%, a distortion rate of ± 2%, and a frequency of 20 Hz. .

Table I footnote * 1: SBR (Nipol 1502) manufactured by Nippon Zeon Co., Ltd.
* 2: Carbon black (Seast KH) manufactured by Tokai Carbon Co., Ltd.
* 3: Zinc oxide manufactured by Shodo Chemical Co., Ltd. (3 types of zinc oxide, average particle size 0.5 μm, specific surface area 5 m ² / g)
* 4: Nano zinc white (average particle size: 34 nm, specific surface area: 30 m ² / g) manufactured by CI Kasei Co., Ltd.
* 5: Stearic acid (bead stearic acid YR) manufactured by Nippon Oil & Fats Co., Ltd.
* 6: Anti-aging agent 6C (SANTOFLEX 6PPD) manufactured by FLEXSYS
* 7: Tsurumi Chemical Industry Co., Ltd. oil-treated sulfur (Jinhua stamp fine powder sulfur 151 mesh)
* 8: Vulcanization accelerator CZ (Noxeller CZ-G) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

Comparative Example 1 is an example in which ZnO is not blended, and the crosslink density (M100) does not increase. Comparative Example 2 is a case where the normal use amount is reduced to 1/3, and Comparative Example 3 is a normal use example.
Example 1 has a higher breaking strength than Comparative Examples 2 and 3, and other physical properties are almost the same as Comparative Example 2.
In Example 2, the modulus is higher than that of Comparative Example 3, tan-δ (60 ° C.) is lower than that of Comparative Example 3, and the fuel efficiency is excellent.

  According to the present invention, the blending amount of zinc oxide in the rubber composition can be remarkably reduced without substantially adversely affecting the physical properties of the rubber composition.

Claims (6)

  A rubber composition comprising (i) at least one diene rubber, (ii) carbon black and / or silica, (iii) sulfur, and (iv) zinc oxide having an average particle diameter of less than 80 nm as a vulcanization accelerator.   Claims formed by blending 20 to 150 parts by weight of carbon black and / or silica, 1 to 5 parts by weight of sulfur and 0.01 to 5 parts by weight of zinc oxide having an average particle diameter of less than 80 nm with respect to 100 parts by weight of diene rubber. Item 2. The rubber composition according to Item 1. The rubber composition according to claim 1 or 2, wherein the specific surface area of zinc oxide is 10 m ² / g or more.   The rubber composition according to any one of claims 1 to 3, wherein the zinc oxide is produced by a gas phase method.   Diene rubber is styrene-butadiene copolymer rubber (SBR), natural rubber (NR), polyisoprene rubber (IR), polybutadiene rubber (BR), butyl rubber (IIR), chloroprene rubber (CR), nitrile rubber (NBR) The rubber composition according to any one of claims 1 to 4, which is at least one selected from ethylene-propylene-diene terpolymer rubber (EPDM).   It is for pneumatic tires, The rubber composition of any one of Claims 1-5.