JPH0741600A - Tire tread rubber composition - Google Patents

Abstract

PURPOSE:To obtain a tire tread rubber composition having excellent wear resistance and resiliency by adding a specified amount of carbon black having specified selected properties to a synthetic diene rubber and/or a natural rubber. CONSTITUTION:The rubber composition is prepared by adding 30-100 pts.wt. carbon black having the following specified selected properties (1) to (8): (1) 75<=N2SA(m<2>/g)<=125, (2) 70<=CTAB(m<2>/g)<=120, (3) 90<=Tint(%)<=125, (4) 105<=24 M4DBP(ml/100g)<=130, (5) 0.60<=DELTADst/Dst<=0.95, (6) 18<=dn(nm)<=28, (7) CTAB +5.83(dn)<225, and (8) V<=3.5X10<-10> (wherein N2SA is the nitrogen adsorption specific surface area, CTAB is the CTAB specific surface area, Tint is the specific tinting power, 24M4DBP is the DBP absorption under compression, Dst is the Stokes modal diameter, DELTADst is the half width of the distribution of the Stokes modal diameters, dn is the particle diameter, and V is the rate of water adsorption) to 100 pts.wt. rubber component comprising a synthetic diene rubber and/or a natural rubber.

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 a tire tread member for passenger cars and light trucks, and more specifically, a rubber composition for a tire tread having high impact resilience while maintaining excellent wear resistance. Regarding

[0002]

2. Description of the Related Art There are various varieties of carbon black for rubber reinforcement depending on the characteristics of the rubber, and these varieties characteristics are major factors for determining various performances of a composition compounded with rubber. For this reason, in the case of compounding with rubber, a means for selecting and using carbon black having a variety of characteristics suitable for use as a member is generally used.

For example, in recent years, fuel-efficient tires have been actively developed in order to meet social demands for resource saving and energy saving, but such a fuel-efficient tire has a relatively small particle size. A rubber composition containing a large amount of carbon black of a large variety in a rubber component in a relatively small amount and having low heat buildup and high impact resilience is effective. However, the compounding of carbon black rubber with a large particle size and a small specific surface area is effective for the purpose of improving fuel economy performance,
The deterioration of surface properties such as braking performance and wear resistance on wet road surfaces cannot be avoided. Therefore, if it is possible to simultaneously impart high wear resistance and low heat buildup that gives high impact resilience to a compounded rubber using a carbon black having a small particle size and a large specific surface area, it is ideal as a rubber member for a tire tread. Will be things.

The applicant of the present invention has added the above-mentioned characteristic properties of carbon black incorporating anti-rubber performance, in particular, basic properties such as particle size, specific surface area and structure, in addition to further microscopic selective properties. We are systematically continuing research to achieve both, and have already made the following development proposals. (1) Nitrogen adsorption specific surface area (N ₂ SA) is 60m ² / g or more, compressed DB
Carbon black with a P of 112 ml / 100 g or more, which maintains the Stokes mode diameter and distribution of the aggregate above a certain value, is a carbon black capable of simultaneously imparting high reinforcing performance and high impact resilience to compounded rubber. 1-53978
Issue). (2) N ₂ SA 60 m ² / g or more, DBP 108 ml / 100 g or more, the true specific gravity value per constant specific surface area is set to a specific range significantly lower than that of known carbon black, and the coloring power and distribution per aggregate mode diameter are set. A rubber composition having a high abrasion resistance and a high impact resilience, which is blended with carbon black having a characteristic of keeping the width above a certain value (JP-A-59).
-140241 publication). (3) N ₂ SA is 65 to 84 m ² / g, and the ratio of N ₂ SA / iodine adsorption amount (IA) is 1.10 to 1.35.
A carbon black (special characteristics) that can simultaneously impart high abrasion resistance and high impact resilience to a compounded rubber in which a relational expression with variables such as BP, blackness, iodine adsorption amount and aggregate mode diameter is set to a certain value or more. (Kaisho 62-58792). (4) N ₂ SA 75-105 m ² / g, compressed DBP 110 ml
/ 100g or more, the true specific gravity value per constant specific surface area is set to a specific range lower than that of the known carbon bralac, and the particle aggregate void diameter and the distribution width per aggregate mode diameter are maintained above a certain value. A carbon black capable of imparting both high abrasion resistance and high impact resilience to the compounded rubber (JP-A-1-201367). (5) Nitrogen adsorption specific surface area (N ₂ SA) belongs to the hard system region of 60 to 100 m ² / g, and the mode diameter (Dp) of the inter-aggregate pores is Dp ≦ 1.543 × (Dst mode diameter) −55.0 ] Blended with the furnace carbon black that satisfies the relational expression of
A low heat-generating rubber composition having excellent abrasion resistance while maintaining a high level of impact resilience (JP-A-4-209640).

In addition, US Pat. No. 4,360,627 discloses N ₂ SA85 for tire tread rubber.
~ 95m ² / g, 24M4 DBP100 ~ 104ml / 100g, T
Disclosed is a carbon black that achieves high wear resistance and high impact resilience with an aggregate Stokes mode diameter distribution (ΔD ₅₀ ) of 180 mμ or more at int 95 to 105%, and US Pat. No. 4,548,980 discloses that N _{2 is used} as a carbon black property for obtaining low rolling resistance and high wet grip performance required for energy-saving tires.
SA 75-105 m ² / g, N ₂ SA-IA ≧ 15, N ₂ S
A-CTABSA≤5, 24M4 DBP≤110, Tint
90 to 110 and ΔTint ≦ −3 are shown.

However, the quality requirements for fuel-efficient tires are becoming more and more advanced, and under the present circumstances, there is a continuing demand for the development of a rubber composition having both a higher level of impact resilience and abrasion resistance. In order to meet such a demand, the applicant has further established that 75 ≦ N ₂ SA (m ² / g) ≦ 12.
5, 70 ≤ CTAB (m ² / g) ≤ 120, 90 ≤ Tint (%) ≤
125, 105 ≤ 24 M4DBP (ml / 100g) ≤ 130, 0.
60 ≦ ΔDst / Dst ≦ 0.95, 18 ≦ dn (nm) ≦ 2
8, CTAB + 5.83 (dn) <225 carbon black having a selective characteristic is a diene-based synthetic rubber and /
Alternatively, a rubber composition for a tire tread has been developed, which is compounded in a ratio of 30 to 100 parts by weight with respect to 100 parts by weight of natural rubber (Japanese Patent Application No. 5-18167).

[0007]

The rubber composition for tire tread according to the above-mentioned prior art was developed by clarifying the technical causal relationship between the particle colloidal properties of carbon black and the compounded rubber performance, which is different from the prior art. It has both impact resilience and wear resistance suitable for tire tread rubber of passenger cars and light trucks.

However, in the subsequent development process, if a limited item concerning the water adsorption rate is newly added to the selective characteristics of the carbon black according to the prior art, the abrasion resistance and the impact resilience of the compounded rubber are balanced in a high level range. I confirmed that I got it.

The present invention was developed on the basis of the above findings, and its object is a tire having a high level of wear resistance and impact resilience suitable for tread rubber of tires for passenger cars and light trucks. It is to provide a rubber composition for a tread.

[0010]

The rubber composition for a tire tread according to the present invention for achieving the above object has the following (1) with respect to 100 parts by weight of a rubber component comprising a diene synthetic rubber and / or natural rubber. Characteristically, the carbon black having the selective properties of (8) to (8) is blended in a proportion of 30 to 100 parts by weight. (1) 75 ≤ N ₂ SA (m ² / g) ≤ 125 (2) 70 ≤ CTAB (m ² / g) ≤ 120 (3) 90 diameter ≤ Tint (%) ≤ 125 (4) 105 ≤ 24 M4DBP (ml / 100g) ≤ 130 (5) 0.60 ≤ ΔDst / Dst ≤ 0.95 (6) 18 ≤ dn (nm) ≤ 28 (7) CTAB + 5.83 (dn) <225 (8) V ≤ 3.5 x ^10-10 However, in the above equation, N ₂ SA is specific surface area by nitrogen adsorption, C
TAB is the CTAB specific surface area, Tint is the specific coloring power (comparative sample IRB # 3), 24M4DBP is the compressed DBP oil absorption, Dst
Is the Stokes mode diameter of the carbon black aggregate measured by a disc centrifuge (DCF), ΔDst is the half-value width of the Stokes diameter distribution, dn is the electron microscope average particle diameter, V is the temperature of 22 to 23 ° C. and relative humidity of 92 to The moisture adsorption rate per unit area at an exposure time of 2400 seconds when the dry carbon black is exposed to 94% is shown.

The values obtained by the following measuring methods are used for the respective characteristics of the carbon black having the above structure. N ₂ SA (nitrogen adsorption specific surface area); ASTM D3037
-88 "Standard Test Method for Carbon Black-Surf
ace Area by Nitrogen Absorption “Method B.
The N ₂ SA measurement value of IRB # 6 by this method is 76 m ²
/ g. CTAB specific surface area; ASTM D3765-89 "Stan
dard Test Method for Carbon Black-CTAB (Cetyltrimet
hylammonium Bromide) Surface Area ". The measured CTAB specific surface area of IRB # 6 by this method is 77
m ² / g. Tint (specific coloring power); JIS K6221-82 "Testing method for carbon black for rubber", paragraphs 6.1.3,
The control sample is measured as IRB # 3. The measured value of IRB # 6 by this method is 100. 24M4DBP (compressed DBP oil absorption); ASTM D349
3-91 "Standard Test Method for Carbon Black-
n-Dibutyl Phthalate Absorption Number of Compresse
d Sample ”. IRB # 6 24M4D by this method
The BP measurement is 87 ml / 100 g.

Dst, ΔDst; A dry carbon black sample was 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 was sufficiently dispersed by ultrasonic waves. Use as a sample. Disk centrifuge device (made by Joyes Lobel, UK)
Is set to a rotation speed of 8000 rpm, 10 ml of a spin solution (2 wt% glycerin aqueous solution) is added, and then 1 ml of a buffer solution (20 vol% ethanol aqueous solution) is injected. Then,
0.5 ml of carbon black dispersion is added with a syringe to start centrifugal sedimentation, and at the same time, a recorder is operated to optically create a Stokes equivalent diameter distribution curve of the carbon black aggregate. The maximum frequency of Stokes equivalent diameter in the obtained distribution curve is defined as Dst (nm), and the difference between two large and small Stokes equivalent diameters at which 50% of maximum frequency is obtained is ΔDst.
(nm). The Dst of IRB # 6 measured by this method is 92.
nm and ΔDst are 68 nm.

Dn (average particle diameter of electron microscope): A carbon black sample is dispersed in chloroform with an ultrasonic cleaner at a frequency of 28 kHz for 30 seconds, and then the dispersed sample is fixed on a carbon support membrane [For details, see "Powder physical properties" for example. Illustration ”(Powder Engineering Study Group et al.) P68 (C)“ Water Surface Membrane Method ”]. This is directly magnified 20000 with an electron microscope.
2 times, the total magnification is 80,000 to 100,000 times, the diameter of 1000 carbon black particles is randomly measured from the obtained photograph, and the arithmetic mean particle diameter (dn) is calculated from the histogram created by dividing every 3 nm. . V (moisture adsorption rate); 1.000 g of carbon black dried under reduced pressure at 110 ° C. for 1 hour and allowed to cool under reduced pressure was placed on a balance in a glove box at a temperature of 22 to 23 ° C. and a relative humidity of 92 to 94%. Then, the change in weight of carbon black due to water adsorption is measured every time, and an increase curve (W) of water adsorption is obtained. From this curve W exposure time 2400
The water adsorption rate V per unit area in seconds is calculated by the following formula. V = δW / δt

The furnace carbon black having the characteristics of the present invention is provided in the furnace head with a combustion chamber having a tangential air supply port and a combustion burner mounted in the furnace axial direction, and is connected coaxially with the combustion chamber. Using an oil furnace containing a three-stage narrow-diameter reaction chamber and a wide-diameter reaction chamber with a raw oil injection nozzle, the feed oil split introduction conditions, fuel oil and air supply amounts, and oxygen gas addition conditions It can be manufactured by adjusting

The above carbon black is blended in a conventional manner with diene synthetic rubber such as isoprene rubber, polybutadiene rubber, butyl rubber and styrene butadiene rubber, natural rubber or a mixed rubber of the diene synthetic rubber and natural rubber. The compounding ratio of carbon black is set to 30 to 100 parts by weight with respect to 100 parts by weight of the rubber component. If the amount of carbon black compounded is less than 30 parts by weight, sufficient abrasion resistance will not be imparted to the compounded rubber, and if it exceeds 100 parts by weight, the viscosity of the compounded compound will increase and the kneading processability will remarkably deteriorate. Upon compounding, the rubber composition for a tire tread of the present invention is obtained by kneading together with necessary components such as a vulcanizing agent, a vulcanization accelerator, an antioxidant, a vulcanization aid, a softening agent and a plasticizer.

[0016]

The selective characteristic items of the carbon black specified in the present invention function as follows for each compounded rubber. That is, N ₂ SA is 75 to 125 m ² / g, CTAB
70-120 m ² / g, Tint 90-125%, 24M4D
The range of BP of 105 to 130 ml / 100 g is a requirement for maintaining a high degree of wear resistance and an appropriate low heat buildup. If N ₂ SA, CTAB, Tint and 24M4DBP are below the above lower limits, sufficient wear resistance cannot be imparted. On the contrary, when N ₂ SA and CTAB exceed the above-mentioned upper limits, the heat buildup tends to increase and the impact resilience tends to decrease. Further, when Tint is out of the upper limit value, exothermicity is increased, and the dispersibility of carbon black in the rubber component is lowered, and when 24M4DBP exceeds the upper limit value, the viscosity of the compounded rubber is increased and the workability is lowered.

The value of ΔDst / Dst is an index showing the aggregate distribution width of carbon black, and this value is 0.6.
If it is less than 0.95, the heat generation property increases, and if it exceeds 0.95, the wear resistance decreases. When the dn is less than 18 nm, the basic particles constituting the carbon black aggregate become too small and the exothermicity is promoted. On the other hand, when the dn exceeds 28 nm, the reinforcing performance deteriorates.

Generally, there is a relationship between dn of carbon black and CTAB, and CTAB decreases as dn increases. However, both of them are [CTAB + 5.83 (d
n) <225], that is, constant d
When CTAB is relatively small with respect to n, the surface area of the aggregate exhibits a unique property of being small despite the fact that the diameter of one basic particle constituting the aggregate is small. It is possible to impart low exothermic properties at the same time. Carbon black having a characteristic that does not satisfy the above relational expression cannot obtain sufficient rubber performance required for a tire tread in either one or both of abrasion resistance and low heat buildup.

Although the water adsorption rate of carbon black is closely related to the surface properties of particles, the carbon black of the present invention having a water adsorption rate V of 3.5 × 10 ^-10 or less is ^superior to conventional carbon black. It is characterized by a low water adsorption rate and a low amount and reactivity of active sites effective for water adsorption on the surface of carbon black. The mechanism of water adsorption to carbon black is complicated. For example, it can be predicted that the rate of water adsorption decreases when there are few hydrophilic surface functional groups or many hydrophobic surface functional groups. It may be physically adsorbed. The carbon black of the present invention has few active sites related to water adsorption, but has many active sites for polymers, and this unique property improves interaction when compounded with a rubber component to improve abrasion resistance to compounded rubber. It is presumed that it fulfills the function of imparting low heat buildup without damaging it.

The properties and functions of the compounded carbon black as described above can act comprehensively to impart a well-balanced high level of impact resilience showing excellent wear resistance and low heat buildup to the rubber composition at the same time. It will be possible.

[0021]

EXAMPLES Examples of the present invention will be described below in comparison with comparative examples.

Examples 1 to 3, Comparative Examples 1 to 6, Reference Examples 1 to 1
3 Combustion chamber (diameter 900 mm, length 1000 mm) having a tangential air supply port and a combustion burner installed in the furnace axial direction at the furnace head, and a feedstock oil injection that penetrates the furnace wall coaxially with the combustion chamber First-stage narrow-diameter reaction chamber equipped with a nozzle (Example: 200 m diameter
m, length 600 mm, comparative example diameter 220 mm, length 400 mm), 2nd stage narrow diameter reaction chamber (Example 180 mm diameter, length 500 mm, comparative example 190 mm diameter, length 500 mm), 3rd stage narrow Diameter reaction chamber (Example diameter 260 mm, length 500 mm, comparative example diameter 240 mm, length 400 mm),
An oil furnace consisting of a large-diameter reaction chamber and a subsequent large-diameter reaction chamber (diameter 450 mm) was installed. Specific gravity (1
5/4 ℃) 1.073, viscosity (Engla 40/20 ℃) 2.
10, toluene insoluble content 0.03%, correlation coefficient (BMCI) 14
Aromatic hydrocarbon oil of 0 was used, and the specific gravity (1
5/4 ° C.) 0.903 viscosity (cst / 50 ° C.) 16.1, hydrocarbon residue 5.4%, flash point 96 ° C. hydrocarbon oil was used.

Using the above reactor, the feedstock oil and the fuel oil, the production conditions such as the divided feed amount of the feedstock oil, the amount of fuel oil, the amount of air supply, the amount of oxygen gas supply, etc. to each narrow-diameter reaction chamber are changed to produce a furnace carbon. Manufactured black. Corresponding characteristics of the obtained carbon black to generation conditions, Table 1 (Examples 1 to 3, Comparative Examples 1 to 4) and Table 2 (Comparative Examples 5 to 9)
It was shown to. Further, Comparative Examples 7 to 8 shown in Table 2 are the following commercially available hard carbon black products. Comparative Example 7: N351 [Tokai Carbon Co., Ltd., Seast NH] Comparative Example 8: N339 [Tokai Carbon Co., Seast KH] Comparative Example 9: N220 [Tokai Carbon Co., Ltd. 6]

Next, the carbon black samples shown in Tables 1 and 2 were blended with oil-extended styrene-butadiene rubber [JSR1712, manufactured by Japan Synthetic Rubber Co., Ltd.] at the blending ratio shown in Table 3.

[0025]

[Table 3]

Various rubber tests were carried out on each rubber composition obtained by vulcanizing the compound of Table 3 at a temperature of 145 ° C. for 50 minutes, and the measurement results are also shown in Tables 1 and 2. The rubber properties were measured as follows. Abrasion amount: Lambourn abrasion tester (mechanical slip mechanism)
Was measured under the following conditions. The results are shown as a relative index when the carbon black of Comparative Example 7 is 100. Test piece: thickness 10 mm, outer diameter 44 mm Emery wheel: GC type, grain size # 80, hardness H added carborundum powder: grain size # 80, addition amount about 9 g / mi
n. Relative slip ratio between emery wheel surface and test piece: 24
%, 60% Test piece rotation speed: 535 rpm Test load: 4 kg

Tan δ (loss coefficient); Visco Elastic Spe
The measurement was performed using a ctrometer (manufactured by Iwamoto Seisakusho) under the following conditions. It should be noted that tan δ (loss coefficient) is an index of heat buildup, and the smaller the measured value, the lower the heat buildup. Test piece: thickness 2 mm, length 30 mm, width 5 mm Frequency: 50 Hz Dynamic strain rate: 1.2% Temperature: 60 ° C. Other characteristics: According to JIS K6301 "Vulcanized rubber physical test method".

From Tables 1 and 2, the rubber compositions of the examples have the same level of particle properties, but have the same wear resistance and an index of exothermicity as compared with the comparative examples which deviate from the selective characteristic requirements of the present invention. Tan δ (loss coefficient) is significantly decreased,
It is recognized that the wear resistance and the impact resilience are well balanced at a high level. Further, the other reinforcing properties are also maintained at a high level, and the overall rubber physical properties are extremely suitable for tire treads of passenger cars and light trucks.

[0029]

As described above, according to the present invention, by selectively regulating the micro colloidal properties and surface properties of carbon black different from those of the prior art, it is possible to maintain a high wear resistance while maintaining excellent wear resistance. A rubber composition for a tire tread that exhibits impact resilience can be provided. Therefore, it can be applied to a tire tread member for passenger cars and light trucks to effectively reduce fuel consumption.

[Table 1]

[Table 2]

Claims (1)

[Claims] 1. The following (1) to (8) with respect to 100 parts by weight of a rubber component comprising a diene synthetic rubber and / or natural rubber.
30 to 100 carbon black having selective characteristics of
A rubber composition for a tire tread, which is blended in a ratio of parts by weight. (1) 75 ≦ N ₂ SA (m ² / g) ≦ 125 (2) 70 ≦ CTAB (m ² / g) ≦ 120 (3) 90 ≦ Tint (%) ≦ 125 (4) 105 ≦ 24 M4DBP (ml / 100g) ≤ 130 (5) 0.60 ≤ ΔDst / Dst ≤ 0.95 (6) 18 ≤ dn (nm) ≤ 28 (7) CTAB + 5.83 (dn) <225 (8) V ≤ 3.5 x 10 ^-10 However, in the above formula, N ₂ SA is the nitrogen adsorption specific surface area, C
TAB is the CTAB specific surface area, Tint is the specific coloring power (comparative sample IRB # 3), 24M4DBP is the compressed DBP oil absorption, Dst
Is the Stokes mode diameter of the carbon black aggregate measured by a disc centrifuge (DCF), ΔDst is the half-value width of the Stokes diameter distribution, dn is the electron microscope average particle diameter, V is the temperature of 22 to 23 ° C. and relative humidity of 92 to The moisture adsorption rate per unit area at an exposure time of 2400 seconds when the dry carbon black is exposed to 94% is shown.