JP2000281833A - Rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition that retains electrical conductivety and low heat build-up without deterioration in processability and abrasion resistance and shows excellent wet grip performance. SOLUTION: This rubber composition comprises 100 pts.wt. of natural rubber and/or diene synthetic rubber, 20-100 pts.wt. of silica-immobilized carbon black as a reinforcing filler and 5-30 pts.wt. of aluminum hydroxide with an average particle size of 0.1-10 μm and BET specific surface area of >=20 m2/g.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition which is excellent in wet grip performance while maintaining electrical conductivity and low heat generation without reducing processability and wear resistance.

[0002]

2. Description of the Related Art In recent years, characteristics required for automobile tires include not only fuel efficiency but also fuel efficiency.
There are a wide variety of things such as steering stability, wear resistance, and riding comfort, and various devices have been devised to improve these performances. Among these performances, the grip performance and the rolling resistance characteristics of the tire are all characteristics relating to the hysteresis loss of the rubber. Generally, when the hysteresis loss is increased, the grip force is increased and the braking performance is improved, but the rolling resistance is also increased and the fuel efficiency is increased.
As described above, since the grip performance and the rolling resistance characteristic are in a contradictory relationship, various rubber compositions for tires have been proposed to simultaneously satisfy both characteristics.

For example, in a rubber composition for a tire, since a polymer component and carbon black greatly affect both properties, when a styrene-butadiene copolymer is used as the polymer component, the content of bound styrene, butadiene The 1,2-bond content of the portion is appropriately selected to improve both the rolling resistance characteristics and the grip performance.

[0004] On the other hand, with respect to carbon black, if the particle diameter is increased or the blending amount is reduced, the cut chipping resistance and the like are reduced. Developed and effective.

[0005] However, generally, when the grip performance is improved, there is a problem that abrasion resistance, which is a property contradictory to the grip performance, is reduced.

[0006] In recent years, for example, European Patent No. 501227 discloses a rubber composition for a tire tread having improved wet performance by devising a method of kneading with special silica and a method for producing the same. JP-A-7-149950 and JP-A-8-5
JP-A-9893 and JP-A-8-59894 discloses a tire tread in which natural rubber or diene rubber is mixed with carbon black and / or an inorganic filler such as silica and aluminum hydroxide to improve wet performance. A rubber composition, Japanese Patent Application Laid-Open No. 9-255814, discloses a tire tread in which carbon black, aluminum hydroxide and / or clay are blended with a rubber having a styrene content of 30 to 40% by weight to improve wet performance. Japanese Patent Application Laid-Open No. 10-59713 discloses a rubber composition for a tire tread using aluminum hydroxide having a specific center particle diameter, a BET specific surface area and a pore diameter as a reinforcing agent. . However, in the former case, the processability of the rubber is deteriorated by blending a large amount of silica, and the electrical conductivity of the rubber is reduced to cause a problem of generation of static electricity. In the latter case, there is a problem that the wet skid performance is not sufficient.

Further, Japanese Patent Application Laid-Open No. 10-316800 discloses
Japanese Patent No. 2788212 and WO 96/37547 disclose a rubber composition in which carbon black having silica fixed to the surface is blended, and the rubber composition is compared with a conventional one using a silica filler. Although it is described that the resistance is small, it is still insufficient in terms of wet skid performance.

Various proposals have hitherto been made to solve these problems. However, wet grip performance without lowering workability and abrasion resistance, and maintaining electric conductivity and low heat build-up. At present, there is no rubber composition excellent in the above.

[0009]

DISCLOSURE OF THE INVENTION The present invention is directed to a rubber composition which solves the above problems and has a good balance of electric conductivity, low heat generation and wet grip performance without lowering workability and wear resistance. It was made as a result of intensive studies to provide products.

That is, the present invention relates to natural rubber and
Or) 100 parts by weight of diene-based synthetic rubber
As a filler, carbon black with silica immobilized
20 to 100 parts by weight and an average particle diameter of 0.1 to 10 μm
m and BET specific surface area is 20m ^Two/ G or more aluminum hydroxide
Rubber composition containing 5 to 30 parts by weight of
Regarding 1).

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The rubber component used in the rubber composition of the present invention is a natural rubber (NR) and / or a diene-based synthetic rubber. The diene-based synthetic rubber is not particularly limited. For example, styrene-butadiene rubber (SBR), polybutadiene rubber (BR), polyisoprene rubber (IR), ethylene-propylene-diene rubber (EPDM), chloroprene rubber (CR) And acrylonitrile-butadiene rubber (NBR).
These may be used alone or in combination of two or more.

Next, the rubber composition of the present invention contains carbon black on which silica is fixed and aluminum hydroxide.

Examples of the carbon black having silica immobilized thereon include carbon black having silica adhered or deposited on the surface (hereinafter referred to as silica surface-treated carbon black), and carbon black and silica in a single particle. One in which silica and carbon black are dimensionally mixed and both silica and carbon black are exposed on the particle surface (hereinafter, referred to as silica-containing carbon black) is exemplified. With the above structure, wear resistance,
Although excellent in electrical conductivity, etc., since the number of functional groups present on the surface is small, chemical affinity with the rubber component is low, and it is possible to improve the disadvantage of silica that it is difficult to disperse by kneading, silica And the advantages of carbon black can be effectively exhibited.

The silica surface-treated carbon black is
The carbon black is produced by, for example, but not limited to, for example, producing carbon black by an oil furnace method or the like, and then putting the carbon black into an atmosphere in which white carbon is produced, and attaching silica to the surface of the carbon black. As an example, the method described in JP-A-63-63755 is cited.
Above, preferably adjusted to 10 to 11, while maintaining the temperature at 70 ° C. or higher, preferably 85 to 95 ° C., for example, hydrolyze sodium silicate to deposit or deposit amorphous silica on the surface of carbon black particles. Can be manufactured. When manufactured by such a method, not all of the silica is physically or chemically bonded to the carbon black surface, but according to transmission electron microscope observation, silica is present on the carbon black. Has been confirmed to be.

The silica-containing carbon black is not particularly limited. For example, there is a method in which an organic siloxane is reacted with a raw material oil to produce the same. Manufacturing methods are preferred. The preferred production method is disclosed in detail, for example, in WO 96/37547.

Examples of the carbon black that can be used include, but are not limited to, HAF, ISAF, SAF and the like.

The silica-containing carbon black is preferable in view of the affinity with the rubber component and the like as compared with the silica surface-treated carbon black, since both the carbon part and the silica part are exposed on the particle surface. Specific examples of the silica-containing carbon black include, for example, ECOBLACK (CRX2000 (trade name)) manufactured by Cabot Corporation.

The content of silica in the carbon black on which the silica is fixed is preferably 0.1 to 30% by weight, more preferably 0.3 to 20% by weight. If the content is less than 0.1% by weight, the effect of improving wet performance tends to be small, and if it is more than 30% by weight, electric conductivity and workability tend to be poor.

The nitrogen adsorption specific surface area (hereinafter, referred to as N ₂ SA) of the carbon black having the immobilized silica.
Is 70 to 300 m ² / g, and further 100 to 250 m ²
/ G is preferred. When the N ₂ SA is less than 70 m ² / g, the dispersibility improving effect and the reinforcing effect tend to be small, and when it exceeds 300 m ² / g, the dispersibility becomes poor,
Exothermicity tends to increase and durability tends to decrease.

The compounding amount of the carbon black having the silica fixed thereto is 2 parts by weight based on 100 parts by weight of the rubber component.
0 to 100 parts by weight, preferably 30 to 80 parts by weight. If the compounding amount is less than 20 parts by weight, sufficient electric conductivity cannot be obtained, and if it exceeds 100 parts by weight, the kneading workability is deteriorated in spite of a small effect of improving abrasion resistance, which is not preferable. .

The aluminum hydroxide is a component used to further improve wet skid performance while maintaining other properties.

The average particle size of the aluminum hydroxide is as follows:
From the viewpoint of the balance between wet skid performance and wear resistance, the thickness is 0.1 to 10 μm, preferably 0.1 to 5 μm. If the average particle size is smaller than 0.1 μm, kneading processability is reduced, although improvement in grip performance cannot be expected.
If it exceeds 0 μm, the wear resistance is undesirably reduced.

[0023] The BET specific surface area of aluminum hydroxide (hereinafter referred to as BET) is, in terms of the balance between the grip performance improvement and wear resistance, 20 m ² / g or more, preferably 30~500m ² / g, further Preferably 50 to
350m ² / g, particularly preferably 70~350m ² / g
It is. When the BET is less than 20 m ² / g, the effect of improving grip performance is reduced, the wear resistance is reduced, and
If it exceeds 00 m ² / g, the dispersibility tends to decrease.

The amount of the aluminum hydroxide is 5 to 30 parts by weight, preferably 10 to 25 parts by weight, based on 100 parts by weight of the rubber component. When the amount is less than 5 parts, the effect of improving wet grip performance is small, and when the amount exceeds 30 parts by weight, abrasion resistance becomes poor, which is not preferable.

The rubber composition of the present invention may further contain, in addition to the above, vulcanizing agents such as silica, silane coupling agents, sulfur, various vulcanization accelerators, various softening agents, which are commonly used in the rubber industry. Additives such as various antioxidants, zinc oxide, stearic acid, antioxidants, and antiozonants can be added.

[0026]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but these do not limit the present invention.

(Raw material) Diene synthetic rubber SBR1502: SBR1 manufactured by JSR Corporation
502 (trade name) (styrene-butadiene copolymer) NIPOL9520: NIPOL manufactured by Zeon Corporation
9520 (trade name) (styrene-butadiene copolymer,
Oil extension: 37.5 phr) Carbon black with silica immobilized CRX2000: CRX2000 manufactured by Showa Cabot
(Trade name) (N ₂ SA: 154.3 m ² / g, DBP oil absorption: 113 ml / 100 g, iodine adsorption surface area: 122
g / kg, silica content: 4.7% by weight) Aluminum hydroxide Aluminum hydroxide A: Heidilite H-43 manufactured by Showa Denko KK (average particle diameter: 0.6 μm, BET: 6.5)
m ² / g) Aluminum hydroxide B: UF- manufactured by Sumitomo Chemical Co., Ltd.
ATH250 (average particle size: 2.5 μm, BET: 25
0 m ² / g) Aluminum hydroxide C: synthesized by the synthesis method described in JP-A-10-59713 (average particle diameter: 2)
μm, BET: 60 m ² / g) Silica: Ultrasil VN3 (N
₂ SA: 210 m ² / g) Carbon black: Show Black N220 manufactured by Showa Cabot Corporation (N ₂ SA: 125 m ² / g) Silane coupling agent: Si69 (bis (3-triethoxysilylpropyl) tetra manufactured by Degussa) Sulfide) Aroma oil: JOMO manufactured by Japan Energy Co., Ltd.
Process X140 Special wax: Sunnock N manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Antioxidant: Nocrack 6 manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
C (N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine) Stearic acid: Stearic acid manufactured by NOF CORPORATION Zinc oxide: Zinc flower No. 1 manufactured by Mitsui Kinzoku Mining Co., Ltd. Sulfur: powder sulfur manufactured by Tsurumi Chemical Co., Ltd. Vulcanization accelerator A: Noxeller NS (N-tert-butyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinko Chemical Co., Ltd. Vulcanization accelerator B : Noxeller D (N, N'-diphenyl guanidine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

(Processability) According to the Mooney viscosity measurement method specified in JIS K6300, the Mooney viscosity ML (1 + 4) of a predetermined rubber composition was measured at 130 ° C. and indicated as an index. The higher the value, the lower the Mooney viscosity,
Indicates excellent workability.

(Abrasion resistance) A predetermined rubber composition was heated at 170 ° C.
Using a vulcanized rubber obtained by press vulcanization for 20 minutes using a Lambourn abrasion tester, the wear amount was measured at a temperature of 20 ° C., a slip ratio of 20%, and a test time of 5 minutes.
The volume loss of each formulation was calculated, and the loss amount of Comparative Example 1 was calculated as 100.
The exponent was expressed by the following equation. The larger the value, the better the wear resistance.

Wear index = (Loss of Comparative Example 1 / Loss of each compound) × 100

(Rolling resistance index)
Using a vulcanized rubber obtained by press vulcanization at 70 ° C for 20 minutes, a viscoelastic spectrometer VES (manufactured by Iwamoto Seisakusho)
Tan δ of each formulation was measured under the measurement conditions of a temperature of 70 ° C., an initial strain of 10%, and a dynamic strain of 2%, and the ta of Comparative Example 1 was measured.
The index was expressed by the following equation with nδ being 100. The larger the value, the better the rolling resistance characteristics.

Rolling resistance index = (tan δ of Comparative Example 1 /
Tan δ) × 100 for each formulation

(Wet skid index) A tire having a tire size of 185 / 65R14 obtained by applying a predetermined rubber composition to a tread and vulcanizing at 170 ° C. for 20 minutes, a domestically produced FF vehicle (displacement: 1800 cc) was used. , 64km / h
The braking distance on an asphalt wet road surface when ABS control was performed under the condition of / h was measured and indicated by an index. The larger the value, the better the wet skid performance.

(Volume specific resistance)
A rubber sheet obtained by vulcanizing at 0 ° C. for 20 minutes was cut in a direction parallel to the roll axis to prepare a rubber test piece provided with a predetermined electrode, and the test piece was held at 23 ± 2 ° C. for 48 hours. Thereafter, the resistance value R between the electrodes was measured at the same temperature, and the volume specific resistance Rv (Rv = (a × b × R) / L) was calculated. Here, a and b represent the thickness of the rubber specimen and the width of the rubber specimen, respectively, and L represents the distance between the measurement electrodes.

Examples 1 to 3 and Comparative Examples 1 to 9 The raw materials shown in Table 1 were blended so as to have the composition shown in Table 1, and kneaded with a Banbury mixer according to a conventional method to obtain various rubber compositions. And used for each evaluation. Table 1 shows the results
Shown in

[0036]

[Table 1]

From the results shown in Table 1, the rolling resistance and the wet skid characteristics of Comparative Example 3 using only carbon black having silica immobilized were improved to some extent as compared with Comparative Example 1 using ordinary carbon black. You can see that it is. However, in Examples 1 to 3 in which predetermined aluminum hydroxide was used in combination with carbon black on which silica was fixed, the rolling resistance characteristics and the wet skid characteristics were further improved.

[0038]

According to the present invention, it is possible to obtain a rubber composition which is excellent in wet grip performance while maintaining electrical conductivity and low heat generation without lowering workability and wear resistance.

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Claims (1)

[Claims] Claims 1. A natural filler and / or a diene-based synthetic rubber, based on 100 parts by weight, as a reinforcing filler, 20 to 100 parts by weight of carbon black on which silica is fixed and an average particle diameter of 0.1 to 100 parts by weight. the rubber composition BET specific surface area was blended 5 to 30 parts by weight or more of aluminum hydroxide 20 m ² / g in 10 [mu] m.