JP3816541B2 - Rubber composition - Google Patents

Description

【００２１】
【表２】

【００２２】
次に、表１および表２の各カーボンブラック試料を表３に示す配合比により天然ゴムに配合した。
【００２３】
【表３】

【００２４】
表３の配合物を１４５℃の温度で４０分間加硫して得られた各ゴム組成物につき各種ゴム試験をおこない、その測定結果を表４（実施例）および表５（比較例、参考例）に示した。なお、ゴム特性の測定は下記によった。このうち、摩耗量は参考例２のカーボンブラックを１００とした場合の相対指数で示した。また、ｔａｎδ（損失係数）は発熱性の指標となるもので、測定値が小さくなるほど発熱度が低いことを示す。
摩耗量；
ランボーン摩耗試験機（機械式スリップ機構）を用い、次の条件で測定した。
試験片：厚さ１０mm、外径４４mm
エメリーホイール：ＧＣタイプ、粒度 #８０、硬度Ｈ
添加カーボランダム粉：粒度 #８０、添加量 約９g/min.
エメリーホイール面と試験片の相対スリップ率：２４％、６０％
試験片回転数：５３５rpm
試験荷重：４kg
【００２５】
ｔａｎδ（損失係数）;
Visco Elastic Spectrometer（岩本製作所製）を用い、次の条件で測定した。
試験片：厚さ２mm、長さ３０mm、幅５mm
周波数：５０Hz
動的歪率：１．２％
温 度：６０℃
その他の特性；
ＪＩＳ Ｋ６３０１「加硫ゴム物理試験法」によった。
【００２６】
【表４】

【００２７】
【表５】

【００２８】
表４および表５から、実施例の結果は同水準のＮ₂ ＳＡを有しながら本発明の選択的特性要件を外れる比較例、参考例に比べ、発熱性の指標となるｔａｎδ（損失係数）と耐摩耗性が相対的に同時に改善されていることが認められる。また、その他の補強特性も高水準に維持されていることが判る。
【００２９】
【発明の効果】
以上のとおり、本発明によれば従来技術とは異なるカーボンブラックのミクロなコロイダル性状を選択規制することによりトラック、バス等を対象とする大型タイヤ用トレッド部材として好適な高い反発弾性を備える低発熱性と優れた耐摩耗性能を兼備するゴム組成物を提供することができる。したがって、トラックやバスに装着して効果的な低燃費化を図ることが可能となる。[0001]
[Industrial application fields]
The present invention relates to a rubber composition suitable as a tread member for a large tire to be mounted on a truck, a bus or the like, and more particularly to a rubber composition having both excellent wear resistance and low heat build-up.
[0002]
[Prior art]
There are various varieties of carbon black for reinforcing rubber depending on the characteristics of the rubber, and these varieties are the main factors for determining the performance of the composition blended with rubber. For this reason, a means for selecting and using carbon black having a variety of characteristics suitable for member applications is usually used in blending with rubber.
[0003]
For example, for rubber members that require a high degree of wear resistance under severe driving conditions such as large tire treads for trucks, buses, etc., the particle size is small such as SAF (N110) and ISAF (N220). Therefore, it is effective to apply carbon black having a large specific surface area. However, since this type of hard carbon black has the property of increasing the heat build-up of the compounded rubber, there is a risk of accelerating the destruction of the internal structure and the aging of the constituent materials due to heat storage during running when the tire tread is used. . Recently, low fuel consumption tires have been actively developed in order to meet social demands for resource and energy savings. However, in order to develop low fuel consumption tires, imparting low heat generation is an indispensable element. For this reason, if carbon black with 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 gives high resilience to the compounded rubber, it is ideal as a rubber member for tire treads. It will be something.
[0004]
The present applicant has conducted research to balance the above-mentioned contradictory rubber performance by adding more micro-selective characteristics in addition to the basic characteristics such as particle diameter, specific surface area, and structure of compounded carbon black. It has continued systematically and has already made the following development proposals.
(1) Carbon black in which the nitrogen adsorption specific surface area (N ₂ SA) is 60 m ² / g or more and the compressed DBP is 112 ml / 100 g or more, and the Stokes mode diameter and the distribution of the aggregates are maintained at a certain value or more. (Japanese Patent Publication No. 1-53978).
(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 significantly lower than that of known carbon black, and coloring power and distribution per aggregate mode diameter A rubber composition containing carbon black having a characteristic of maintaining a width above a certain value (Japanese Patent Laid-Open No. 59-140241).
(3) A rubber composition containing carbon black having an N ₂ SA in the range of 100 to 200 m ² / g and having a broad aggregate Stokes diameter distribution relative to the particle diameter (Japanese Patent Laid-Open No. 63-112638) Issue gazette).
(4) A rubber composition containing carbon black having N ₂ SA in the range of 70 to 185 m ² / g and having ^two local maximum points in the aggregate Stokes diameter distribution (Japanese Patent Laid-Open No. 63-179941) )
(5) Carbon in which N ₂ SA is in a range of 110 to 155 m ² / g, and a value defined by a formula using DBP, compressed DBP, blackness, N ₂ SA, and iodine adsorption amount as a variable is in a specific range. A rubber composition containing black (Japanese Patent Laid-Open No. 63-297439).
[0005]
[Problems to be solved by the invention]
According to these prior arts, it is possible to obtain a rubber composition having both high wear resistance and low heat build-up improved for large tire treads. However, the quality requirements for fuel-efficient tires are becoming increasingly sophisticated, and the current situation is that there is a continuing demand for the development of rubber compositions that achieve a higher level of wear resistance and low heat generation.
[0006]
Based on such a request, the present invention has been developed by elucidating the technical causal relationship between the particle colloidal properties of carbon black different from the prior art and the compounded rubber performance, and its purpose is trucks, buses, etc. An object of the present invention is to provide a rubber composition having both high wear resistance and low heat generation suitable as a tread member of a large tire targeting the above.
[0007]
[Means for Solving the Problems]
The rubber composition according to the present invention for achieving the above object belongs to a hard system region having a CTAB specific surface area of 100 to 160 m ² / g and a compressed DBP of 95 to 115 ml / 100 g, and has the following relational formula (1) A feature of the constitution is that the furnace carbon black having the selective characteristics according to the above (3) 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) 1.13 Dst mode diameter −40.92 ≦ ΔDst ≦ 1.13 Dst mode diameter −30.92
(3) Dp mode diameter ≤ 2.66 Dmp mode diameter -15.516
In the formula (1), N ₂ SA represents the nitrogen adsorption specific surface area, and IA represents the iodine adsorption amount. The Dst mode diameter in the equation (2) indicates the Stokes mode diameter of the carbon black aggregate measured by the disc centrifuging device (DCF), and ΔDst indicates the half width of the Stokes diameter distribution. The Dp mode diameter in equation (3) is the maximum frequency mode diameter in the pore diameter distribution between carbon black aggregate grains measured by a differential scanning calorimeter (DSC), and the Dmp mode diameter is carbon black obtained by the mercury intrusion method. The maximum frequency mode diameter in the pore diameter distribution between aggregate grains is shown.
[0008]
Values obtained by the following measuring methods are used for the characteristics of the carbon black having the above-described configuration.
CTAB specific surface area;
According to ASTM D3765-89 “Standard Test Method for Carbon Black-CTAB (Cetyltrimethylammonium Bromide) Surface Area”. The measured CTAB specific surface area of IRB # 6 by this method is 77 m ² / g.
Compressed DBP (24M4DBP);
According to ASTM D3493-91 "Standard Test Method for Carbon Black-N-Dibutyl Phthalate Absorption Number of Compressed Sample". The measured value of the compressed DBP oil absorption of IRB # 6 by this method is 87 ml / 100 g.
N ₂ SA (nitrogen adsorption specific surface area);
According to ASTM D3037-88 “Standard Test Method for Carbon Black-Surface Area by Nitrogen Absorption” Method B. The measured N ₂ SA value of IRB # 6 by this method is 76 m ² / g.
IA (iodine adsorption amount);
According to JIS K6221 (1982) “Testing method of carbon black for rubber”, 6.1.1. The measured iodine adsorption of IRB # 6 by this method is 80 mg / g.
[0009]
Dst mode diameter, ΔDst;
A dry carbon black sample is mixed with a 20 vol% aqueous ethanol 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 to prepare a sample. The disc centrifuging device (manufactured by Joyes Lobel, UK) is set at a rotation speed of 8000 rpm, 10 ml of spin solution (2 wt% glycerin aqueous solution) is added, and 1 ml of buffer solution (20 vol% ethanol aqueous solution) is injected. Next, 0.5 ml of the carbon black dispersion is added with a syringe to start centrifugal sedimentation, and at the same time, the recorder is operated to create a distribution curve of the Stokes equivalent diameter of the carbon black aggregate optically. The Stokes equivalent diameter of the maximum frequency in the obtained distribution curve is defined as the Dst mode diameter (nm), and the difference between the two large and small Stokes equivalent diameters at which 50% of the maximum frequency is obtained is defined as ΔDst (nm). IRB # 6 obtained by this measurement method has a Dst mode diameter of 92 nm and ΔDst of 68 nm.
[0010]
Dp mode diameter;
After drying according to JIS K6221 (1982) 5 “How to make a dry sample”, a precisely-collected carbon black sample is mixed with distilled water to prepare a paste having a carbon black concentration of 0.250 g / cm ^3. Thoroughly disperse with sound waves. Within 10 minutes after ultrasonic dispersion, measurement of the distribution of aggregate intergranular pores is started with a differential scanning calorimeter (DSC, DSC30 manufactured by Mettler). In this case, the amount of paste collected is in the range of about 3 to 5 mg. After being put in an aluminum sample container and sealed, the mass of the paste is confirmed and set in the DSC apparatus. Then, measure in the next step.
(1) Rapidly cool from room temperature to -80 ° C.
(2) Heat from −80 ° C. to −5 ° C. at a rate of 10 ° C./min.
(3) Heat from −5 ° C. to −0.1 ° C. at a rate of 1 ° C./min., And hold at −0.1 ° C. (temperature lower by 0.1 ° C. than the freezing point of distilled water) for 10 minutes.
(4) 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) of each temperature (in increments of 0.1 ° C) is read from the compensation energy chart obtained in step (4), and the pores between the aggregate grains are calculated from the following equations (1) and (2). Diameter (Dp) and pore diameter distribution (ΔV / ΔDp) are obtained.
Dp = (135.34 / ΔT) +1.14 (1)
ΔV / ΔDp = K · (ΔT) ² / (Wa · y) (2)
In equations (1) and (2), ΔT is the freezing point depression width of distilled water, Wa is the heat of solidification of distilled water, and K is a coefficient taking into account the sensitivity of the DSC apparatus and the mass of the sample. These equations were derived by Brun et al. And are described in detail in Thermochimica Acta, 21 (1977) 59-88 “A NEW METHOD FOR THE SIMULTANEOUS DETERMINATION OF THE SIZE AND THE SHAPE OF PORES: THE THERMOPOROMETRY”. The Dp mode diameter of IRB # 6 measured by this method is 95.3 nm.
[0011]
Dmp mode diameter;
After charging 0.2 g of carbon black pellets adjusted to a particle size of 0.25 to 0.50 mm in a special cell (3 ml) of a mercury porosimeter (Pore Sizer 9300 manufactured by Micromeritics), a pressure of 25 to 2000 lb / in ² Press the mercury in the range of, and measure the pressure at the point where the amount of mercury intrusion increases rapidly. From this pressure value, the pore diameter between aggregate grains of carbon black is calculated and set as the Dmp mode diameter (nm). The Dmp mode diameter of IRB # 6 measured by this method is 40 nm.
[0012]
A furnace carbon black having the characteristics of the present invention comprises a combustion chamber having a tangential air supply port at the furnace head and a combustion burner mounted in the furnace axial direction, and a feedstock oil coaxially connected to the combustion chamber. Using an oil furnace furnace composed of multistage narrow and wide diameter reaction chambers with injection nozzles, the conditions for dividing and introducing the feedstock oil, the amount of fuel oil and air, and the conditions for adding oxygen gas are adjusted. Can be manufactured.
[0013]
The above furnace carbon black is blended in accordance with conventional methods into elastomers such as natural rubber, styrene butadiene rubber, polybutadiene rubber, isoprene rubber, butyl rubber, other rubbers that can be reinforced with conventional carbon black, and mixed rubber. 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 kneaded together with necessary components such as a vulcanizing agent, a vulcanization accelerator, an anti-aging agent, a vulcanization aid, a softening agent, and a plasticizer. Thus, the rubber composition of the present invention is obtained.
[0014]
[Action]
Among the furnace carbon black characteristic items specified in the present invention, the particle properties of CTAB specific surface area of 100 to 160 m ² / g and compressed DBP of 95 to 115 ml / 100 g belong to the hard system region. This is a precondition for maintaining exothermicity. If the CTAB specific surface area is less than 100 m ² / g, sufficient wear resistance for large tires will not be imparted. On the other hand, if it exceeds 160 m ² / g, the dispersibility for rubber will deteriorate and the wear resistance will be smooth. Since it does not improve and heat build-up increases, it becomes difficult to use it as carbon black for low fuel consumption tires. On the other hand, if the compressed DBP is less than 95 ml / 100 g, the wear resistance is insufficient, and if it exceeds 115 ml / 100 g, the viscosity at the time of rubber blending increases and the workability is lowered.
[0015]
The characteristic of the relational expression (1) is an element that mainly suppresses heat generation. When the value of (N ₂ SA-IA) is less than 5, the heat generation required for a rubber composition for a fuel-efficient tire is reduced. On the other hand, if this value exceeds 15, the viscosity at the time of rubber compounding becomes high and the practicality becomes poor. If the aggregate distribution (ΔDst) of the carbon black involved in the relational expression (2) becomes too wide, the wear resistance retreat becomes large, and conversely, if it becomes too narrow, the effect of suppressing the heat generation is reduced. Therefore, the range of [1.13 Dst mode diameter −40.92 ≦ ΔDst ≦ 1.13 Dst mode diameter −30.92] regulated by the relational expression (2) is optimal for imparting a high level of wear resistance and low heat generation to the compounded rubber. The aggregate distribution range is large.
[0016]
Relational expression (3) is also a characteristic element that functions to achieve both high wear resistance and low heat generation. That is, the mode diameter of carbon black aggregate intergranular pores is a parameter indicating the properties of an aggregate (aggregate) in which carbon black is firmly fused and bonded, and the value varies depending on the measurement method. The Dp mode diameter measured by a differential scanning calorimeter (DSC) is the pore diameter between aggregate grains in a state where carbon black is dispersed in distilled water, and therefore, compared with the Dmp mode diameter obtained by the mercury intrusion method. The measured value increases. According to the study by the inventors, it was confirmed that general carbon black on the market has a relationship of the following formula.
Dp mode diameter = (2.66 Dmp mode diameter−8.343) ± 5
For example, the measured value of the Dp mode diameter of IRB # 6 is 95.3 nm, but this value falls within the range of the Dp mode diameter (93.1 to 103.1 nm) according to the above formula calculated from the measured Dmp mode diameter of 40 nm. Yes. The Dp mode diameter of the carbon black showing the selective characteristics of the present invention is lower than the value calculated from the above formula in relation to the Dmp mode diameter, and this is specified by the relational expression (3) (2.66 Dmp mode). When it is located at a level equal to or less than the calculated value of diameter-15.516), it functions effectively to improve the wear resistance without impairing the low heat build-up of the compounded rubber.
[0017]
The unique properties and functions of the furnace carbon black blended as described above work together, giving the rubber composition an excellent wear resistance and a low exothermic performance with a high level of resilience at the same time. It becomes.
[0018]
【Example】
Examples 1-4, Comparative Examples 1-3, Reference Examples 1-3
Combustion chamber (diameter: 900 mm, length: 1000 mm) having a tangential air supply port at the head of the furnace and a combustion burner mounted in the direction of the furnace axis, and a feed oil injection nozzle coaxially connected to the combustion chamber and penetrating through the furnace wall First stage narrow diameter reaction chamber (diameter 250 mm, length 500 mm), second stage narrow diameter reaction chamber (diameter 160 mm, length 600 mm), third stage narrow diameter reaction chamber (diameter 180 mm, length 600 mm), And an oil furnace furnace composed of a subsequent wide-diameter reaction chamber (diameter 400 mm) was installed. The feedstock is an aromatic hydrocarbon oil with a specific gravity (15/4 ° C) of 1.073, viscosity (Engler 40/20 ° C) of 2.10, toluene insoluble content of 0.03%, and a correlation coefficient (BMCI) of 140. The fuel oil used was a hydrocarbon oil having a specific gravity (15/4 ° 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.
[0019]
Manufacture furnace carbon black using the above reactor, feedstock oil and fuel oil by changing the production conditions such as the split feed rate, feed rate, air feed rate, oxygen gas feed rate, etc. did. The characteristics of the obtained carbon black are shown in Table 1 corresponding to the generation conditions. Table 2 shows the characteristics of commercially available hard carbon black varieties as Reference Examples 1 to 3.
[0020]
[Table 1]

[0021]
[Table 2]

[0022]
Next, each carbon black sample of Table 1 and Table 2 was blended with natural rubber at a blending ratio shown in Table 3.
[0023]
[Table 3]

[0024]
Various rubber tests were performed on each rubber composition obtained by vulcanizing the blends of Table 3 at a temperature of 145 ° C. for 40 minutes, and the measurement results are shown in Table 4 (Examples) and Table 5 (Comparative Examples, Reference Examples). )Pointing out toungue. The rubber properties were measured as follows. Of these, the amount of wear was shown as a relative index when the carbon black of Reference Example 2 was taken as 100. Further, tan δ (loss factor) is an index of heat generation, and the lower the measured value, the lower the heat generation.
Amount of wear;
Using a 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, grain size # 80, hardness H
Added carborundum powder: particle size # 80, added amount about 9g / min.
Relative slip ratio between emery wheel surface and specimen: 24%, 60%
Test piece rotation speed: 535 rpm
Test load: 4kg
[0025]
tan δ (loss factor);
Measurement was performed under the following conditions using a Visco Elastic Spectrometer (manufactured by Iwamoto Seisakusho).
Test piece: 2mm thick, 30mm long, 5mm wide
Frequency: 50Hz
Dynamic distortion: 1.2%
Temperature: 60 ° C
Other characteristics;
According to JIS K6301 "Vulcanized Rubber Physical Test Method".
[0026]
[Table 4]

[0027]
[Table 5]

[0028]
From Tables 4 and 5, the results of the examples are the same level of N ₂ SA, but the tan δ (loss factor) that is an index of heat generation compared to the comparative examples and reference examples that deviate from the selective characteristic requirements of the present invention. It can be seen that the wear resistance is improved relatively simultaneously. It can also be seen that other reinforcing properties are maintained at a high level.
[0029]
【The invention's effect】
As described above, according to the present invention, low heat generation with high resilience suitable as a tread member for large tires for trucks, buses, etc. by selectively regulating the micro colloidal properties of carbon black different from the prior art. It is possible to provide a rubber composition having both properties and excellent wear resistance. Therefore, it is possible to achieve an effective reduction in fuel consumption by being mounted on a truck or bus.

Claims (1)

Furnace carbon black belonging to a hard system region having a CTAB specific surface area of 100 to 160 m ² / g and a compressed DBP of 95 to 115 ml / 100 g and having selective characteristics according to the following relational expressions (1) to (3) A rubber composition comprising 35 to 100 parts by weight per 100 parts by weight of the component.
(1) 5 ≦ N ₂ SA-IA ≦ 15
(2) 1.13 Dst mode diameter −40.92 ≦ ΔDst ≦ 1.13 Dst mode diameter −30.92
(3) Dp mode diameter ≤ 2.66 Dmp mode diameter -15.516
In the formula (1), N ₂ SA represents the nitrogen adsorption specific surface area, and IA represents the iodine adsorption amount. The Dst mode diameter in equation (2) is the Stokes mode diameter of the carbon black aggregate measured by a disc centrifuging device (DCF), and ΔDst is the half-value width of the Stokes diameter distribution. The Dp mode diameter in Eq. (3) is the maximum frequency mode diameter in the pore diameter distribution between carbon black aggregate particles measured by a differential scanning calorimeter (DSC), and the Dmp mode diameter is carbon black obtained by the mercury intrusion method. The maximum frequency mode diameter in the pore diameter distribution between aggregate grains is shown.