JPH04270741A - Rubber composition - Google Patents

Abstract

PURPOSE:To obtain a rubber composition suitable for large-sized tire tread for truck, bus, etc., to be used under a severe traveling condition. CONSTITUTION:100 pts.wt. rubber component consisting of 40-80 pts.wt. natural rubber and/or isoprene rubber and 20-60 pts.wt. polybutadiene is blended with 30-70 pts.wt. carbon black having the following selective characteristics to give a rubber composition. The rubber composition satisfying (1) 100<=N2 SA (m<2>/g)<=160 (2) 100<=24M4DBP oil absorption (ml/100g)<=120 (3) Dst mode diameter (nm)>=0.2X24M4DBP-0.6XN2 SA+137 has much more improved wear resistance under a severe condition than a rubber composition not satisfying the conditions.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition suitable for use in tire tread members, particularly a rubber composition exhibiting excellent wear resistance for use in large tire treads used under severe conditions.

0002

2. Description of the Related Art Improving wear life is one of the most important performance requirements for large tires for trucks, buses, etc. Conventionally, measures to improve this demand from the perspective of tread rubber have been taken, such as increasing the amount of carbon black blended, blending butadiene rubber with natural rubber, and suppressing the addition of softeners such as process oil. ing.

For example, in this type of rubber composition, the rubber component has a trans-1,4-bond content of 50 to 80.
% butadiene rubber and natural rubber in a weight ratio of 5/95 to 7
Truck and bus tires with abrasion resistance and cut resistance suitable for treads consisting of carbon black with a ratio of 0/30 and filled with N2 SA of 120 m2/g or more (Japanese Unexamined Patent Publication No. 182332/1999), butadiene Rubber component 100 consisting of 15 to 70 parts by weight of rubber and 30 to 85 parts by weight of natural rubber and/or isoprene rubber
Cecyltrimethylammonium bromide (CTAB) adsorption specific surface area 140-150m2/by weight
g and DBP oil absorption 130-150ml/100
Rubber composition for large tire treads containing 30 to 75 parts by weight of carbon black (JP-A-2-18554)
Publication No. 3) have been proposed.

However, the measures taken in the prior art to improve wear resistance are not necessarily sufficient for the required purpose. In other words, by increasing the amount of carbon black blended in the rubber, it is possible to improve wear resistance up to the upper limit of the appropriate blending range, but if the blending exceeds that range, it will not only reduce the wear resistance but also improve heat resistance. This leads to deterioration in processability due to a decrease in properties and a marked increase in the viscosity of the compound. In addition, although an improvement in abrasion resistance is observed even when the amount of butadiene rubber added is increased, the improvement effect is insufficient, and when trying to improve abrasion resistance by suppressing the addition of a softener, the viscosity of the compound increases at the same time. This causes a decrease in workability.

[0005]

[Problems to be Solved by the Invention] After extensive research into the relationship between rubber components and blended carbon black properties, the present invention has found that a rubber component that is a blend of natural rubber and/or polyisoprene rubber with polybutadiene rubber has been developed. demonstrated that, in addition to the conventionally known highly structured carbon black formulation, a carbon black formulation with a relatively large aggregate Stokes mode diameter can significantly improve wear resistance under particularly harsh usage conditions. This is what led to the development.

[0006] Accordingly, an object of the present invention is to provide a rubber composition that exhibits excellent wear resistance for use in large tire treads.

[0007]

[Means for Solving the Problems] A rubber composition according to the present invention for achieving the above object has a rubber component consisting of 40 to 80 parts by weight of natural rubber and/or polyisoprene rubber and 20 to 60 parts by weight of polybutadiene rubber. To 100 parts by weight, 3 parts of carbon black having the following selective properties were added.
The composition is characterized in that it is blended in a proportion of 0 to 70 parts by weight. (1) 100 ≦ N2 SA ≦ 160 (2
) 100 ≦ 24M4DBP ≦ 120 (3
) Dst ≧ 0.2×24M4DBP- 0.6
×N2 SA+137 However, N2 SA is the nitrogen adsorption specific surface area (m2/g), 24M4DBP is the compressed DBP oil absorption (ml/100g), and Dst is the Stokes mode diameter of the maximum frequency in the Stokes diameter distribution of aggregates determined by centrifugal sedimentation method (nm). ).

[0008] For each characteristic of the carbon black having the above structure, values obtained by the following measuring method are used. N2 SA ASTM D3037-88 “Standard
Test Method for Carbon B
rack-SurfaceArea by Nitro
gen Absorption “By MethodB. 24M4DBP ASTM D3493-85a “Standard
Test Method for Carbon B
rack-Dibutyl Phthalate Abs
Ortion Number of Compresions
Dst 20% dry carbon black with a small amount of surfactant
Carbon black concentration is 50 by mixing with ethanol aqueous solution.
A dispersion liquid of mg/l is prepared, and this is sufficiently dispersed by ultrasonic waves to prepare a sample. Disc centrifuge device (D
CF) at a rotational speed of 8000 rpm, and after adding 10 ml of spin liquid (2% glycerin aqueous solution),
Inject 1 ml of buffer solution (ethanol aqueous solution). Next, 0.5 ml of the sample is added using a syringe to start centrifugal sedimentation, and at the same time, a recorder is activated 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 the Dst mode diameter.

The rubber component used in the present invention has a composition in which 20 to 60 parts by weight of polybutadiene rubber is blended with 40 to 80 parts by weight of natural rubber, polyisoprene, or a mixed rubber thereof. Polybutadiene rubber is added to improve the abrasion resistance of the rubber component, but if the amount is less than 20 parts by weight, the effect of improving the abrasion resistance is insufficient,
If it exceeds the weight part, the appearance will deteriorate.

On the other hand, among the carbon black characteristic items specified in the present invention, when N2 SA is less than 100 m2/g, the wear resistance particularly under less severe conditions decreases,
If it exceeds m2/g, the viscosity of the unvulcanized rubber becomes too high and processability deteriorates. 24M4DBP is 100ml/1
If it is less than 00 g, the abrasion resistance will be insufficient especially under severe conditions, and if it is more than 120 ml/100 g, the dispersibility in rubber will decrease and processability will be impaired. Also, Dst
Mode diameter is [0.2×24M4DBP- 0.6×N
2 SA+137 ] If the above requirements are not met, the carbon black aggregate becomes relatively too small, resulting in poor dispersion into rubber, making it impossible to impart sufficient wear resistance. Therefore, if all the requirements regarding these rubber components and carbon black properties are satisfied, the rubber composition will have wear resistance suitable for tread members of large tires.

[0011] Carbon black having the above characteristics is
A combustion chamber having an air supply port tangential to the furnace head and a combustion burner mounted in the axial direction of the furnace, and a first stage narrow-diameter reaction chamber, a second stage narrow-diameter reaction chamber, and a wide-diameter reaction chamber coaxially arranged. Using an oil furnace with a structure in which
It can be produced by controlling combustion conditions, raw material oil supply conditions, etc. in a process in which the fuel is divided into a stage narrow-diameter reaction chamber and a second stage narrow-diameter reaction chamber.

The rubber component consisting of natural rubber and/or polyisoprene rubber and polybutadiene rubber and the above-mentioned carbon black are blended according to a conventional method and added with a vulcanizing agent, a vulcanization accelerator, an anti-aging agent, a vulcanization aid, and a softening agent. , and knead with necessary ingredients such as plasticizer. The blending ratio of carbon black is
The rubber component is set in a range of 30 to 70 parts by weight per 100 parts by weight. When this blending ratio is less than 30 parts by weight, sufficient reinforcing performance cannot be obtained, and when it exceeds 70 parts by weight, dispersion becomes poor.

[0013]

[Operation] The problems that arise when blending carbon black into the rubber component of natural rubber and/or polyisoprene rubber and polybutadiene rubber, which is the object of the present invention, are as follows:
These are the distribution of carbon black to each rubber phase and the dispersion of carbon black in each rubber phase. If the distribution of carbon black in each rubber phase is uneven or if the dispersion is insufficient, it is difficult to obtain good wear resistance.

However, the carbon black specified in the present invention, which has a high structure and a relatively large Stokes mode diameter of the aggregate, is subjected to a larger shearing force during the kneading process with the rubber component, so that it is not evenly distributed in each rubber phase. And dispersed evenly. Excellent wear resistance is imparted through this action. In particular, the improvement in abrasion resistance is particularly effective when carbon black with high structural characteristics is blended, and highly practical abrasion resistance performance is exhibited under high input usage conditions.

[0015]

[Example] A combustion chamber (diameter 900 mm) equipped with a tangential air supply port at the furnace head and a combustion burner installed in the axial direction of the furnace.
, length 1000 mm), and a first stage narrow-diameter reaction chamber (diameter 200 mm, length 6) coaxially connected to the combustion chamber.
00 mm), a second stage narrow-diameter reaction chamber (diameter 160 mm, length 600 mm) and a subsequent wide-diameter reaction chamber (diameter 400 mm).
mm), using an oil furnace with a first raw material oil spray nozzle in the first stage reaction chamber and a second raw material oil spray nozzle in the second stage reaction chamber, four types were generated by changing the generation conditions. produced carbon black. The raw material oil has a specific gravity (15/4 °C) of 1.073 and a viscosity (Engler 40
/20℃) 2.10, toluene insoluble content 0.03%,
Aromatic hydrocarbon oil with a correlation coefficient (BMCI) of 140,
In addition, the fuel oil has a specific gravity (15/4 °C) of 0.903, a viscosity (Cst/50 °C) of 16.1, and a residual carbon content of 5.4%.
, a hydrocarbon oil with a flash point of 96°C was used. Table 1 shows the generation conditions, and Table 2 shows the characteristics of the obtained carbon black with the type code (
A to D) are displayed in correspondence with each other. Incidentally, type codes F and H in Table 2 are commercially available carbon blacks that have a high structure but do not meet the selective characteristic requirements of the present invention.

[0016]

[0017]

Examples 1 to 4, Comparative Examples 1 to 5 Natural rubber (NR) was prepared using each carbon black (CB) shown in Table 2.
and a rubber component consisting of polybutadiene rubber (BR), and the mixture was vulcanized at a temperature of 145° C. for 50 minutes to prepare a rubber composition. A Lambourn abrasion test and a Pico abrasion test were conducted on each of the obtained rubber compositions, and the results are shown in Table 3 in comparison with the rubber compounding ratio.

[0019] The measurement of the wear test was carried out as follows, and the measured value was expressed as an index when the wear amount of Comparative Example 1 was set as 100 [(Comparative Example 1 wear amount)/(Sample wear amount) x 100
]. ■ Lambourn abrasion test Abrasion resistance under low severity conditions was measured using a Lambourn abrasion tester (manufactured by Iwamoto Seisakusho Co., Ltd.) under the following conditions. Test piece: Thickness 10 mm, outer diameter 44 mm Emery wheel: GC type, particle size 80, hardness H-added carborundum powder: particle size 80 mesh, addition amount approximately 9 g/m
in. Relative slip rate between emery wheel surface and test piece: 24%
Test piece rotation speed: 535 rpm Test load: 4 kg ■ Pico abrasion test Abrasion resistance under highly severe usage conditions was measured using a Pico abrasion tester in accordance with ASTM D2228.

[0020]

[0021] From the results in Table 3, all Examples 1 to 4 that meet the requirements of the present invention have improved wear resistance, and especially compared to the comparative example, the wear resistance is clearly improved under high-severity usage conditions. An increase is observed.

Examples 5 to 8, Comparative Examples 6 to 9 Natural rubber (N
Rubber compositions were prepared using the blending ratios of R), polybutadiene rubber (BR), and carbon black (CB) as shown in Table 4. All other ingredients and vulcanization conditions were the same as in Table 3. Table 4 shows the abrasion resistance index of the obtained rubber composition in comparison with the compounding conditions.

[0023]

The wear resistance data in Table 4 shows the same tendency as Table 3. Similar results were obtained when the rubber component was a composition of polyisoprene rubber and polybutadiene rubber, or a composition in which polybutadiene rubber was blended with natural rubber and polyisoprene rubber.

[0025]

As described above, according to the present invention, it is possible to provide a rubber composition that exhibits excellent abrasion resistance especially under severe usage conditions. Therefore, it is extremely useful as tread rubber for large tires such as trucks and buses used in harsh driving environments.

Claims (1)

[Claims] Claim 1: 40 to 80 parts by weight of natural rubber and/or polyisoprene rubber and 20 to 6 parts by weight of polybutadiene rubber.
1. A rubber composition comprising 100 parts by weight of a rubber component consisting of 0 parts by weight and 30 to 70 parts by weight of carbon black having the following selective properties. (1) 100 ≦ N2 SA ≦ 160 (2
) 100 ≦ 24M4DBP ≦ 120 (3
) Dst ≧ 0.2×24M4DBP- 0.6
×N2 SA+137 However, N2 SA is the nitrogen adsorption specific surface area (m2/g), 24M4DBP is the compressed DBP oil absorption (ml/100g), and Dst is the Stokes mode diameter of the maximum frequency in the Stokes diameter distribution of aggregates determined by centrifugal sedimentation method (nm). ).