JP3283942B2 - Rubber composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition having a novel property which can effectively reduce the ply loose phenomenon for a tire carcass.

[0002]

2. Description of the Related Art There are many types of furnace carbon black for rubber reinforcement depending on the particle properties, and are usually classified based on characteristics such as average particle diameter, specific surface area and structure. And since these kind characteristics are the main factors to determine various properties of compounded rubber, when compounding with rubber components, means to select and use carbon black with kind characteristics suitable for the material use is commonly used. ing. For example, a tire carcass site must withstand the load received by the tire, impact and filling air pressure, so a high tension area (elongation) is required, but the basic particle size is relatively small for this application, Hard carbon blacks such as N219 (ISAF-Ls) and N326 (HAF-Ls) having a low structure are selectively used.

In recent years, high-speed durability has been strongly required for large tires for trucks and buses, and the radial structure of tires has been progressing, and carcass cords having high elastic modulus such as polyester and steel have been used. Kind is used. For this reason, the expansion and contraction between the cords during running and the shear strain in the cord direction at the time of contact with the ground are increased, so that the rubber portion of the carcass ply is cracked or broken, and as a result, the ply loose phenomenon often occurs. ing. In general, in order to reduce this ply loose phenomenon, it is effective to prevent thermal aging of rubber due to heat generated during running and to reduce fatigue aging due to repeated strain. In order to suppress the heat build-up of the rubber composition,
It is effective to mix carbon black with a large particle size and small specific surface area.However, this type of soft carbon black has a weakening of the breaking strength due to poor reinforcement, and causes a peeling phenomenon between the carcass cord and the rubber. And durability cannot be maintained.

[0004] The applicant of the present invention has developed such a reciprocal rubber performance by adding more microselective characteristics in addition to the basic characteristics such as particle diameter, specific surface area and structure of the compounded carbon black. We have systematically continued research to achieve both, and have already made the following development proposals. (1) Nitrogen adsorption specific surface area (N ₂ SA) of 60 m ² / g or more and DBP oil absorption of 60 to simultaneously impart high reinforcing performance and elongation and low heat build-up to compounded rubber to reduce the ply loose phenomenon. Furnace black for tire carcass belonging to the hard system region of ９０90 ml / 100 g and having a selective characteristic whose true specific gravity is equal to or less than the value calculated from the equation [1.8379-0.0006 × (N ₂ SA)] (Japanese Patent Publication No. 1-54376) No.). (2) Similarly, when the nitrogen adsorption specific surface area (N ₂ SA) is 60 m ² / g or more,
It belongs to a hard type with a BP oil absorption of 60 to 90 ml / 100 g, and has a pore mode radius between aggregates of [43.3524 −0.1892 ×
(N ₂ SA)] A rubber composition having both high breaking strength and elongation and low heat build-up, blended with carbon black having selective properties not more than the value calculated by the formula (Japanese Patent Application No. 4-84649).
No.)

[0005]

According to these prior arts, a rubber composition suitable for a tire carcass can be obtained. However, the use of tires in recent years has become increasingly severe, and the development of carbon black capable of simultaneously imparting even lower heat build-up and higher breaking strength and elongation to rubber compositions for tire carcass has been developed. Is still required.

The present invention has been developed based on such a request by elucidating the technical consequences between the colloidal properties of carbon black different from those of the prior art and the performance of a compounded rubber. It is an object of the present invention to provide a rubber composition suitable for a tire carcass having a high degree of reinforcement, an elongation and a low heat build-up, which can effectively reduce the ply loose phenomenon under a variety of running conditions.

[0007]

The rubber composition according to the present invention for achieving the above object has a CTAB specific surface area of 6%.
0 to 110 m ² / g, a DBP oil absorption of 50 to 90 ml / 100 g belongs to a hard system region, and has the following characteristic formulas (1) to (3).
It is a structural feature that the rubber component is blended at a ratio of 35 to 100 parts by weight with respect to 100 parts by weight of the rubber component. (1) 5 ≦ N ₂ SA−IA ≦ 15 (2) Tint ≧ (blackness + 26) (3) 0.60 ≦ ΔDst / Dst mode diameter ≦ 0.75 where N ₂ SA in equation (1) is nitrogen Adsorption specific surface area (m ² / g), I
A indicates the iodine adsorption amount (mg / g). In the equation (2), Tint represents the specific coloring power (%) with respect to the reference sample IRB # 3, and the blackness represents the blackness (%) with respect to the reference sample IRB # 2. Also,
The Dst mode diameter in equation (3) is the disk centrifuge device
The Stokes mode diameter and ΔDst of the carbon black aggregate measured by (DCF) indicate the half width of the Stokes diameter distribution.

The values obtained by the following measuring methods are used for the characteristics of the furnace carbon black having the above configuration. CTAB specific surface area (CTAB); ASTM D3765-89
“Standard Test Method for Carbon Black-CTAB (Cetyl
trimethylammonium Bromide) According to Surface Area.
The measured value of the CTAB specific surface area of IRB # 6 by this method is:
77 m ² / g. DBP oil absorption (DBP): According to JIS K6221 (1982) "Test method for carbon black for rubber", paragraph 6.1.2, oil absorption A method. The DBP oil absorption of IRB # 6 by this method is 99.0 ml / 100 g. N ₂ SA (nitrogen adsorption specific surface area); ASTM D3037
−88 ”Standard Test Method for Carbon Black-Surf
ace Area by Nitrogen Absorption "According to Method B.
IRB # 6N ₂ SA measured by this method is 76m ² / g. IA (Iodine adsorption amount): According to JIS K6221 (1982) "Test method for carbon black for rubber", section 6.1.1.
The IA measurement of IRB # 6 by this method is 80 mg / g.

Tint (specific coloring power); JIS K6221
(1982) "Testing methods for carbon black for rubber"
According to the item 3, the reference sample is measured as IRB # 3. The Tint value of IRB # 6 by this method is 100%. Blackness: 0.500 g of a dry carbon black sample having a particle size of 149 μm or less was weighed and thoroughly kneaded while dripping linseed oil on a glass plate.
Paste 25x5 on Hoover Mahler with 15lb load
The mixture is kneaded twice to form a thin film on the surface of the measurement glass plate. A dencyclone head was set on a thin film previously formed for the reference sample IRB # 2, and the head was set to 50%. When the head was moved at least three places, the meter value was 49.5 to 50.
Confirm that it is 5%. In this state, the head is placed on the thin film of the sample carbon black, and the meter value is read. The head moves five places, and the average value is used as a measured value to calculate blackness by the following equation. Blackness = 50 / T × 100 where T is the measured value of the sample carbon black, 100 is the blackness of the reference sample IRB # 2, and 50 is the reference sample IRB
# 2 Thin film setting value. The blackness of IRB # 6 by this method is 92%.

Dst mode diameter, ΔDst; A dry carbon black sample is mixed with a 20 vol% ethanol aqueous solution containing a small amount of a surfactant to prepare a dispersion having a carbon black concentration of 50 mg / l, which is sufficiently dispersed by ultrasonic waves. Let it be a sample. Disc Centrifuge (Joyes Lobe, UK)
l) was set to 8000 rpm, 10 ml of spin solution (2 wt% glycerin aqueous solution) was added, and then 1 ml
Buffer solution (20 vol% ethanol aqueous solution). Then, 0.5 ml of the carbon black dispersion is added by a syringe to start centrifugal sedimentation, and at the same time, the recorder is operated to optically create a distribution curve of the Stokes equivalent diameter of the carbon black aggregate. The Stokes equivalent diameter of the maximum frequency in the obtained distribution curve is defined as Dst mode diameter (nm),
The difference between Stokes equivalent diameters at two points, large and small, at which a frequency of 50% of the maximum frequency is obtained is defined as ΔDst (nm). I by this measurement method
RB # 6 has a Dst mode diameter of 92 nm and a ΔDst of 68 nm.

A furnace carbon black having the characteristics of the present invention is provided in a combustion chamber having a tangential air supply port on a furnace head and a combustion burner mounted in a furnace axial direction, and is coaxially connected to the combustion chamber. Using an oil furnace consisting of a multi-stage narrow-diameter reaction chamber and a wide-diameter reaction chamber having a feed oil injection nozzle, divided feed conditions for feed oil, supply amounts of fuel oil and air, and oxygen gas addition conditions It can be manufactured by adjusting such factors.

The above-mentioned furnace carbon black is blended with an elastomer such as natural rubber, styrene-butadiene rubber, polybutadiene rubber, isoprene rubber, butyl rubber, various rubbers which can be reinforced with conventional carbon black, and mixed rubber according to a conventional method. The compounding ratio of carbon black is 35 to 100 parts by weight with respect to 100 parts by weight of the rubber component, and is kneaded together with necessary components such as a vulcanizing agent, a vulcanization accelerator, an antioxidant, a vulcanization aid, a softener, and a plasticizer. Thus, the rubber composition of the present invention is obtained.

[0013]

Among the characteristic items of the furnace carbon black specified in the present invention, the basic particle diameter range of CTAB specific surface area of 60 to 110 m ² / g and the structure range of DBP oil absorption of 50 to 90 ml / 100 g are usually in the hard system area of the variety. It is a prerequisite for the compounded rubber to have high reinforcing performance and moderate heat generation. When the CTAB specific surface area is less than 60 m ² / g, the reinforcing property is remarkably reduced, and on the other hand, 110 m ² / g
Exceeding the limit results in increased heat build-up, making it unsuitable for tire carcass. On the other hand, if the DBP oil absorption is less than 50 ml / 100 g, it becomes difficult to disperse the carbon black at the time of compounding the rubber, so that the reinforcing performance cannot be sufficiently imparted.
If the value exceeds g, the elongation characteristic becomes particularly remarkable.

The characteristic of the relational expression (1) mainly serves as a factor for suppressing the heat build-up. If the value of (N ₂ SA-IA) is less than 5, the heat build-up is insufficiently reduced. If it exceeds 15, the elongation properties decrease and the viscosity at the time of compounding the rubber increases, resulting in deterioration in processability. The selective property related to Tint in the relational expression (2) is an index indicating the property of the aggregate (aggregate) in which the carbon black is firmly fused and bonded, and the blackness indicating the size of the aggregate basic particle diameter. This shows that the coloring power is relatively large as compared with. When Tint is larger than the calculated value of (blackness + 26), sufficient reinforcement and improvement in elongation properties are provided. The (ΔDst / Dst mode diameter) value in the relational expression (3) is an index of the aggregate distribution width of carbon black. When this value satisfies the range of 0.60 to 0.75, the compounded rubber has a high level. And improved low heat build-up.

The unique properties and functions of the above-described furnace carbon black act comprehensively to effectively reduce the ply loose phenomenon as a rubber composition for a tire carcass, and can be used under severe driving conditions. Stability and durability can be greatly improved.

[0016]

【Example】

Examples 1-3, Comparative Examples 1-3, Reference Examples 1-2 A combustion chamber (diameter 800 mm, length 1000 mm) having a tangential air supply port at the furnace head and a combustion burner mounted in the furnace axis direction.
A first-stage narrow-diameter reaction chamber (diameter 250 mm, length 500 mm) and a second-stage narrow-diameter reaction chamber (diameter 180 mm, length) each having a feed oil injection nozzle coaxially connected to the combustion chamber and penetrating through the furnace wall. 300m
m), a third-stage narrow-diameter reaction chamber (diameter 200 mm, length 300 mm), and a subsequent wide-diameter reaction chamber (diameter 450 mm) were installed. The specific gravity (15/4
° C) 1.073, viscosity (engler 40/20 ° C) 2.1
0, toluene insoluble content 0.03%, correlation coefficient (BMCI) 140
Of aromatic hydrocarbon oil, specific gravity (15 /
A hydrocarbon oil having a temperature of 4 ° C) of 0.903, a viscosity (cst / 50 ° C) of 16.1, a residual carbon content of 5.4%, and a flash point of 96 ° C was used.

Using the above-mentioned reactor, raw material oil and fuel oil, the furnace is produced by changing the production conditions such as the divided supply amount, the fuel oil supply amount, the air supply amount, and the oxygen gas supply amount of the raw material oil to each narrow-diameter reaction chamber. Carbon black was produced. The properties of the obtained carbon black are shown in Table 1 in association with the production conditions. Table 2 shows the characteristics of commercially available hard carbon black products as Reference Examples 1 and 2.

[0018]

[Table 1]

[0019]

[Table 2] Table Notes: (1) N326 [Tokai Carbon Co., Ltd., "Seast 300"] (2) N219 [Tokai Carbon Co., Ltd., "Seast 60"
0 "]

Next, each of the carbon black samples shown in Tables 1 and 2 was blended into natural rubber at a blending ratio shown in Table 3.

[0021]

[Table 3]

Each rubber composition obtained by vulcanizing the compound of Table 3 at a temperature of 145 ° C. for 40 minutes was subjected to various rubber tests, and the measurement results are shown in Table 4. In addition, the measurement of the rubber property was based on the following. Of these, tan δ (loss coefficient) is an index of heat build-up, and a smaller measured value indicates a lower heat build-up. tan δ (loss coefficient); Visco Elastic Spectrometer
(Manufactured by Iwamoto Seisakusho) under the following conditions. Test piece: thickness 2 mm, length 30 mm, width 5 mm Frequency: 50 Hz Dynamic strain rate: 1.2% Temperature: 60 ° C. Other properties: According to JIS K6301 “Vulcanized rubber physical test method”.

[0023]

[Table 4]

From the results shown in Table 4, the rubber compositions of Examples 1 to 3 have the same level of specific surface area, but are compared with Comparative Examples and Reference Examples of carbon black formulations which do not satisfy the selective property requirements of the present invention. Ta which is an index of tensile strength, elongation and low heat generation
It was recognized that nδ (loss coefficient) was significantly improved and improved.

[0025]

As described above, according to the present invention, a rubber composition having both high reinforcing performance and low heat build-up suitable for a tire carcass by simultaneously restricting the colloidal properties of carbon black different from the prior art. Things can be provided. Therefore, the ply loose phenomenon under severe driving conditions is effectively reduced, and safety and durability are improved.

Claims (1)

(57) [Claims] (1) a CTAB specific surface area of 60 to 110 m ² / g;
Furnace carbon black belonging to the hard type region having a DBP oil absorption of 50 to 90 ml / 100 g and having selective properties according to the following relational expressions (1) to (3) was added in an amount of 35 to 100 parts by weight based on 100 parts by weight of the rubber component. A rubber composition characterized by being blended in a ratio of parts. (1) 5 ≦ N ₂ SA−IA ≦ 15 (2) Tint ≧ (blackness + 26) (3) 0.60 ≦ ΔDst / Dst mode diameter ≦ 0.75 where N ₂ SA in equation (1) is nitrogen Adsorption specific surface area (m ² / g), I
A indicates the iodine adsorption amount (mg / g). In the equation (2), Tint represents the specific coloring power (%) with respect to the reference sample IRB # 3, and the blackness represents the blackness (%) with respect to the reference sample IRB # 2. Also,
The Dst mode diameter in equation (3) is the disk centrifuge device
The Stokes mode diameter and ΔDst of the carbon black aggregate measured by (DCF) indicate the half width of the Stokes diameter distribution.