JP3510656B2 - Rubber composition - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition suitable as a tire tread member for passenger cars and light trucks, and more particularly to an excellent wear resistance effective for fuel-efficient tires. And a low heat generating rubber composition having high rebound resilience. 2. Description of the Related Art There are various types of carbon black for rubber reinforcement depending on the characteristics of the rubber. The characteristics of these types are main factors for determining various properties of a composition compounded in rubber. It becomes. For this reason, when compounding with rubber, means for selecting and using carbon black having a variety of characteristics suitable for the purpose of the member is usually used. [0003] For example, in recent years, fuel-efficient tires have been actively developed in order to meet the social demands for resource saving and energy saving, but such fuel-efficient tires have a relatively large particle size. A rubber composition having low heat build-up and high rebound resilience in which a large variety of carbon black is blended in a relatively small amount with a rubber component is effective. However, rubber compounding of carbon black having a large particle diameter and a small specific surface area is effective for improving fuel economy performance,
Deterioration of surface characteristics such as braking performance and abrasion resistance on wet road surfaces is inevitable. Therefore, if carbon rubber having a small particle size and a large specific surface area can be used to simultaneously impart high wear resistance and low heat build-up that provides high rebound resilience to a compounded rubber, a tire tread for fuel efficiency reduction It becomes ideal as a rubber member for use. [0004] The applicant of the present invention adds the above-mentioned reciprocal rubber performance to the characteristic aspects of the carbon black to be compounded, in particular, to the basic properties such as particle diameter, specific surface area, structure and the like, as well as more microselective properties. We have systematically continued the research to achieve this, and have already made the following development proposals. (1) Nitrogen adsorption specific surface area (N ₂ SA) is 60m ² / g or more, compressed DBP
A carbon black that can simultaneously impart high reinforcing performance and high rebound resilience to a compounded rubber in which the Stokes mode diameter and the distribution of aggregates are maintained at a certain value or more in a carbon black of 112 ml / 100 g or more (Japanese Patent Publication No. No. 53978)
. (2) N ₂ SA: 60 m ² / g or more, DBP: 108 ml / 100 g or more, the true specific gravity value per specific surface area is set to a specific range that is significantly lower than that of known carbon black, and the coloring power and distribution per aggregate mode diameter are set. A rubber composition having high abrasion resistance and high rebound resilience blended with carbon black for maintaining a width of not less than a certain value (JP-A-59-140241). (3) N ₂ SA is 65 to 84 m ² / g, N ₂ SA / Iodine adsorption amount (I
The ratio of (A) is in the range of 1.10 to 1.35, and the abrasion resistance and the high wear resistance of the compounded rubber whose compression formula DBP, blackness, iodine adsorption amount and agglomerate mode diameter as variables are set to a certain value or more are set. Carbon black capable of simultaneously providing rebound resilience (Japanese Patent Application Laid-Open No. 62-58792). (4) When the N ₂ SA is 75 to 105 m ² / g, the compressed DBP is 110 ml / 100 g or more, the true specific gravity per specific surface area is set to a specific range lower than that of known carbon black, and the particle aggregate void diameter Carbon black (Japanese Patent Application Laid-Open No. 1-201367) which can combine high abrasion resistance and high rebound resilience with a compounded rubber having a distribution width per aggregate mode diameter of a certain value or more. (5) Carbon black having a N ₂ SA of 60 to 100 m ² / g and a relational expression value between the mode diameter Dp of the pores between the aggregate grains and the mode diameter (Dst) of the particle aggregate set to a certain value or less was blended. A rubber composition having both high resilience and abrasion resistance (Japanese Patent Application Laid-Open No. 4-209640). In addition, U.S. Pat. No. 4,360,627 discloses an N ₂ SA of 85 to 95 m ² / for tire tread rubber.
g, 24M4DBP 100-104ml / 100g, Tint 95-105%
And the distribution of aggregate Stokes mode diameter (△ D ₅₀ ) is 180
Carbon black that achieves high abrasion resistance and high rebound resilience of at least nm is disclosed, and U.S. Pat.
In the specification, carbon black characteristics for obtaining low rolling resistance and high wet grip performance required for an energy-saving tire tread rubber include N ₂ SA75-
105m ² / g, N ₂ SA-IA ≧ 15, N ₂ SA-CTABS
A ≦ 5, 24M4DBP ≦ 110, Tint 90-110, ΔTint
≦ −3 is indicated. [0006] However, material requirements for fuel-efficient tires are becoming more and more advanced, and it is difficult for the rubber composition according to the prior invention to meet recent performance requirements. is the current situation. [0007] The inventors of the present invention have succeeded in developing research on such a background and have found that the nitrogen adsorption specific surface area (N ₂ SA) is 75 to 75%.
Furnace carbon black belonging to a hard region of 125 m ² / g and a compressed DBP of 100 to 130 ml / 100 g, wherein the half-width of the Stokes diameter of the aggregate is in the range of a constant relational expression value in relation to the Stokes mode diameter. Further, a rubber composition containing carbon black in which the half width of the pore diameter distribution between aggregate grains is within a range of a constant relational expression value in relation to the mode diameter of the pore diameter distribution is a tire tread for passenger cars and light trucks. The fact that suitable rubber physical properties were obtained was elucidated. The present invention has been developed on the basis of the above facts, and has an object to provide a high level of wear resistance and rebound resilience suitable for treads of fuel-efficient tires for passenger cars and light trucks. Another object of the present invention is to provide a rubber composition having the following. [0009] The rubber composition according to the present invention for achieving the above object has a nitrogen adsorption specific surface area (N ₂ S
A): 76-118 m ² / g, compressed DBP: 106-121 ml
Furnace carbon black that belongs to the hard system region of / 100 g and satisfies the characteristic requirements of the following formulas (1) and (2) is blended at a ratio of 35 to 100 parts by weight to 100 parts by weight of the rubber component. Is a structural feature. However, in the equation (1), Dst represents the Stokes mode diameter of the carbon black aggregate measured by the disk centrifuge (DCF), ΔDst represents the half width of the Stokes diameter distribution, and Dp in the equation (2) The mode frequency of the maximum frequency in the pore size distribution between the carbon black aggregate particles measured by a differential scanning calorimeter (DSC) is shown, and ΔDp is the half width of the pore size distribution between the carbon black aggregate particles. The values obtained by the following measuring methods are used for the respective characteristics of the carbon black having the above-mentioned structure. Nitrogen adsorption specific surface area (N ₂ SA); ASTM D3037-88 “St
andard Test Method for Carbon Black-SurfaceArea by
According to Nitrogen Absorption “Method B. The measured value of IRB # 6 by this method is 76 m ² / g. Compressed DBP; ASTM D3493-85a“ Standard Test
Method for Carbon Black- DibutylPhthalate Absorpti
on Number of Compressed Sample ”. The measured value of IRB # 6 by this method is 87 ml / 100 g. Dst, ΔDst; JIS K6221 (1982)
5 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 liquid with a carbon black concentration of 50 mg / l based on "How to make a dry sample". To make a sample. Disc Centrifuge (Joyes Lobe, UK)
l) set to 8000 rpm and spin liquid (temperature
After adding 10 ml of 2 wt% glycerin aqueous solution at 25 ° C, 1 ml
Buffer solution (20 vol% ethanol aqueous solution at 25 ° C)
Inject. Next, a carbon black dispersion at a temperature of 25 ° C
After 0.5 ml has been added by syringe, centrifugation is started and at the same time the recorder is activated to obtain the distribution curve shown in FIG. The horizontal axis shows the elapsed time after adding the carbon black dispersion with a syringe, and the vertical axis shows the absorbance at a measurement point that changed with the centrifugal sedimentation of the carbon black. Each time T is read from this distribution curve and substituted into the equation (1) to calculate the Stokes equivalent diameter corresponding to each time. ## EQU1 ## Where η: viscosity of the spin solution (0.935 cp) N: disk rotation speed (8000 rpm) r ₁ : radius of carbon black dispersion injection point (4.56 cm) r ₂ : radius to absorbance measurement point (4.82 cm) ) [rho _CB: density of the carbon black _{^{(g / cm 3) ρ l}} : density of the spin fluid (1.00178g / cm ³⁾ maximum frequency in the distribution curve of the thus Stokes equivalent diameter and the absorbance obtained (FIG. 2) Is the Dst mode diameter (nm), and the difference between the Stokes equivalent diameters of the two large and small points at which 50% of the maximum frequency is obtained is ΔDst (nm).
And The Dst mode diameter of IRB # 6 according to this measurement method is 92 nm, and ΔDst is 68 nm. Dp, ΔDp; JIS K6221 (1982) 5
After drying based on “How to make a dry sample”, a precisely weighed carbon black sample is mixed with distilled water to prepare a paste having a carbon black concentration of 0.250 g / cm ³ , and sufficiently dispersed by ultrasonic waves. Within 10 minutes after ultrasonic dispersion, measurement of the distribution of pores between aggregate particles is started using a differential scanning calorimeter (DSC, DSC30 manufactured by Mettler). In this case, the amount of the paste to be collected is in the range of about 3 to 5 mg. After sealing in a sample container made of aluminum, the mass of the paste is confirmed, and the paste is set in the DSC device. Next, measurement is performed in the next step. Cool rapidly from room temperature to -80 ° C. Heat from -80 ° C to -5 ° C at a rate of 10 ° C / min. After heating from -5 ° C to -0.1 ° C at a rate of 1 ° C / min., -0.1 ° C (0.1 ° C lower than the freezing point of distilled water)
Hold for 10 minutes. Cool gradually from -0.1 ° C to -8 ° C at a rate of 0.1 ° C / min. And record the compensation energy. Then, the peak height (y) at each temperature (in increments of 0.1 ° C) is read from the compensation energy chart obtained in step (2), and the pore diameter between aggregate particles (Dp) is obtained from the following equations (1) and (2). ) And pore size distribution (△ V / △ Dp). Dp = (135.34 / ΔT) +1.14 (1) ΔV / ΔDp = K · (ΔT) ² / (Wa × y) (2) In the equations (1) and (2), ΔT represents distilled water. The freezing point depression width, Wa is the heat of solidification of distilled water, and K is a factor taking into account the sensitivity of the DSC device and the mass of the sample. These formulas were derived by Brun et al.
ta, 21 (1977) 59-88 “A NEW METHOD FOR THE SIMULTANE
OUS DETERMINATION OF THE SIZE AND THE SHAPE OF POR
ES: THE THERMOPOROMETRY ”. The maximum frequency pore diameter in the distribution curve obtained by the above method is D
The difference between the pore diameters of the two large and small points at which 50% of the maximum frequency is obtained is ΔDp. Furnace carbon black having the characteristics of the present invention is coaxially connected to a combustion chamber having a tangential air supply port at the furnace head and a combustion burner and a feed oil injection nozzle mounted in the furnace axis direction. It is manufactured by using a normal oil furnace composed of a narrow-diameter reaction chamber and a wide-diameter reaction chamber, and adjusting the supply amounts of raw oil, fuel oil, air, etc., and adding oxygen gas and other conditions. be able to. The above-mentioned furnace carbon black is blended with elastomers 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 rubbers in accordance with a conventional method. The mixing ratio of carbon black is 35 to 100 parts by weight with respect to 100 parts by weight of the rubber component, and it is kneaded together with necessary components such as a vulcanizing agent, a vulcanization accelerator, an antioxidant, a vulcanizing aid, a softener, and a plasticizer. Thus, the rubber composition of the present invention is obtained. In the furnace carbon black characteristic items specified in the present invention, the nitrogen adsorption specific surface area (N ₂ SA) is 75 to 125 m ² /
g and the particle properties of the compressed DBP of 100 to 130 ml / 100 g belong to the hard system region, and are prerequisites for maintaining high abrasion resistance and moderate heat generation in the compounded rubber. If the nitrogen adsorption specific surface area is less than 75 m ² / g, sufficient abrasion resistance cannot be obtained, while if it exceeds 125 m ² / g, heat generation increases, making it difficult to use as carbon black for fuel-efficient tires It becomes.
If the compression DBP is less than 100 ml / 100 g, the abrasion resistance becomes insufficient. On the other hand, if the compression DBP exceeds 130 ml / 100 g, the viscosity of the rubber composition becomes high, and the processability deteriorates, which is not preferable. Dst and ΔDst are characteristics relating to the size and distribution of the carbon black aggregate. ΔDst is an index indicating the distribution of the Stokes equivalent diameter of the aggregate. Reinforcing properties such as abrasion resistance of rubber are reduced, and if the rubber is narrow, rebound resilience is reduced and a low heat-generating material cannot be obtained. According to the study by the inventor, this ΔDst shows a certain correlation with Dst, and the marketed hard carbon black generally has ΔDst = 0.519.
It has been confirmed that there is a relationship of × Dst + 16.6. When ΔDst exceeds the value [0.519 × Dst + 32.6], the wear resistance of the compounded rubber decreases, and when the value falls below the value [0.519 × Dst + 8.0], the heat generation increases. Dp and ΔDp are properties related to the morphology of the carbon black aggregates. In the aggregate structure of the aggregates, which are aggregates of carbon black particles, voids and pores between the aggregate particles, that is, aggregate particles It is an index indicating the size of the pores between them, and their distribution. In addition, it is assumed that the distribution of pores between aggregate grains is affected not only by the size of the aggregate, but also by the variation in the form of each aggregate and the manner of networking between aggregates. The mode diameter Dp at the maximum frequency and the half-value width ΔDp of the pore diameter distribution show a constant correlation, and the ΔD of the hard carbon black marketed
p generally has a relationship of [0.776 × Dp−16.4] ± 14. The range of ΔDp specified in the present invention is characterized by the fact that the distribution width of intergranular pores is wide in relation to Dp, but when ΔDp falls below the value of [0.776 × Dp + 1.5], the exothermicity increases. Is insufficiently controlled, while [0.776 × Dp +
40.5], the wear resistance deteriorates. The present invention provides a Δ
The range of Dst is the same as that of the hard carbon black marketed to Dst, and the range of ΔDp is Dp.
Is characterized by a wide range of relationships. this is,
It is presumed that the size distribution of the aggregate of carbon black is the same as that of general carbon black, but is due to the difference in the form of each aggregate and the network state of the aggregates. In the present invention, the above-mentioned various properties of the carbon black comprehensively act to provide the compounded rubber composition with low heat generation performance having high rebound resilience while maintaining excellent wear resistance. It becomes possible. EXAMPLES Examples of the present invention will be described below in comparison with comparative examples. Examples 1-4, Comparative Examples 1-4 A combustion chamber (diameter 900 mm, length 900 mm) having a tangential air supply port at the furnace head and a combustion burner mounted in the furnace axis direction, coaxial with the combustion chamber First-stage narrow-diameter reaction chamber (diameter 250 mm, length 500 mm) equipped with a raw material injection nozzle that is connected to the furnace wall and penetrates the furnace wall,
An oil furnace composed of a second-stage narrow-diameter reaction chamber (diameter 180 mm, length 600 mm), a third-stage narrow-diameter reaction chamber (diameter 220 mm, length 500 mm) and a wide-diameter reaction chamber (diameter 400 mm) following this A furnace was installed. For feedstock, specific gravity (15/4 ° C) 1.07
3.Viscosity (Engler 40/20 ℃) 2.10, toluene insoluble matter
0.03%, aromatic hydrocarbon oil with a correlation coefficient (BMCI) of 140, specific gravity (15/4 ℃) 0.903, viscosity (Cst / 50
° C), a hydrocarbon oil having 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 first stage, second stage and third stage raw material supply amount, fuel oil amount, air supply amount, oxygen gas Eight types (Examples 1 to 4, Comparative Examples 1 to 4) of furnace carbon blacks were produced by changing the production conditions such as the amount of addition.
Tables 1 and 2 show the conditions for forming carbon black and the characteristics of the obtained carbon black in association with each other. Also,
Table 3 shows the characteristics of commercially available hard carbon black varieties as Reference Examples 1 to 4. [Table 1] [Table 2] [Table 3] Next, these carbon black samples were compounded in styrene-butadiene rubber [JSR1712, manufactured by Nippon Synthetic Rubber Co., Ltd.] at the compounding ratio shown in Table 4. [Table 4] Each rubber composition obtained by vulcanizing the composition of Table 4 at a temperature of 145 ° C. for 50 minutes was subjected to various rubber tests, and the measured results are shown in Table 5 (Example) and Table 6 (Comparative Example). ) And Table 7 (Reference Example). In addition, the measurement of the rubber characteristic was based on the following. Using a wear amount Lambourn abrasion tester (mechanical slip mechanism),
The measurement was performed under the following conditions. Test piece: thickness 10mm, outer diameter 44mm Emery wheel: GC type, particle size # 80, hardness H Carburundum powder with addition: particle size # 80, addition amount about 9g / min. 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) It was measured under the following conditions using a Visco Elastic Spectrometer manufactured by Iwamoto Seisakusho. Test piece: thickness 2 mm, length 30 mm, width 5 mm Frequency: 50 Hz Dynamic strain rate: 1.2% Temperature: 60 ° C. The smaller the value of tan δ, the lower the heat generation. Other properties According to JIS K6301 “Vulcanized rubber physical test method”. [Table 5] [Table 6] [Table 7] From the above results, Examples satisfying the characteristic requirements specified in the present invention are Comparative Examples 1 and 2 which do not satisfy the requirement of the expression (1) and Comparative Examples 3 and 4 which do not satisfy the requirement of the expression (2). In comparison, the abrasion resistance of the compounded rubber is improved while having the same specific surface area, and a reduction in tan δ (loss coefficient), which is an index of heat generation, and an improvement in rebound resilience are recognized, and these characteristics are balanced. It turns out that they are well compatible. Also,
It is clear that the characteristics are significantly improved as compared with the reference example, and the other reinforcing characteristics are also maintained at a high level. As described above, according to the present invention, by controlling the micro characteristics of carbon black different from those of the prior art, low heat build-up with excellent abrasion resistance and high rebound resilience can be achieved. It becomes possible to provide a rubber composition. Therefore, the present invention can be applied to a tire tread member for a passenger car or a light truck to achieve effective fuel saving.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a distribution curve showing changes in absorbance due to centrifugal sedimentation of carbon black and the elapsed time after adding a carbon black dispersion. FIG. 2 is a distribution curve showing the relationship between Stokes equivalent diameter (Dst) and absorbance, and an explanatory diagram of Dst mode diameter and ΔDst.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C08L 21/00-21/02 C08K 3/00-3/40

Claims (1)

(57) Claims 1. The nitrogen adsorption specific surface area (N ₂ SA) is 76 to 118.
Furnace carbon black, which belongs to a hard type region of m ² / g and a compressed DBP of 106 to 121 ml / 100 g and satisfies the characteristic requirements of the following formulas (1) and (2), was added in an amount of 35 parts per 100 parts by weight of the rubber component. A rubber composition characterized by being blended in a proportion of 100 parts by weight. However, in the equation (1), Dst represents the Stokes mode diameter of the carbon black aggregate measured by the disk centrifuge (DCF), ΔDst represents the half width of the Stokes diameter distribution, and Dp in the equation (2) The mode frequency of the maximum frequency in the pore diameter distribution between the carbon black aggregate particles measured by a differential scanning calorimeter (DSC) is shown, and ΔDp is the half width of the pore diameter distribution between the carbon black aggregate particles.