JPH07755B2 - Carbon black for tire tread rubber - Google Patents

Description

TECHNICAL FIELD The present invention relates to a carbon black for a tire tread rubber capable of imparting a high level of wear resistance and low heat buildup to a compounded rubber in a relatively balanced manner.

[Conventional technology]

It has been conventionally considered that the particle size, the specific surface area, the structure, and the like of the rubber reinforcing performance of carbon black are the dominant factors, and there are various varieties depending on the characteristics of the rubber. When compounding with the rubber component, carbon black having a variety of characteristics suitable for the intended member is selected and used. For example, N1 should be used for rubber members that require a high degree of wear resistance under severe driving conditions such as tire treads.
Hard carbon black with a small particle size such as 10, N220 is used.

Recently, the demand for high-speed performance and stable running has increased along with the high performance of automobiles, and particularly for tire treads, there has been an increasing demand for development of rubber performance having excellent wear resistance and low heat generation.

Generally, the wear resistance of rubber increases as the specific surface area or structure incorporated increases, but on the other hand, this type of carbon black gives a result of increasing the heat buildup of the rubber. For this reason, it is extremely difficult to impart high abrasion resistance and low heat buildup to the compounded rubber at the same time by the characteristic elements of conventional standard carbon black.

Therefore, various attempts have been made to solve the above problems by using a special carbon black property (Japanese Patent Publication No. 53-34149, Japanese Patent Publication No. 63-112638, etc.).

[Problems to be Solved by the Invention]

However, conventionally proposed rubber compositions containing carbon black having selective properties are still insufficient to keep abrasion resistance and heat buildup at good levels, and further improvement is required. Is requested. In order to solve this problem, the inventors have studied from a different angle from the prior art and found that carbon black having relatively large aggregate voids in an aggregate having a certain structure level is compounded in a rubber component. It was confirmed that the combination of high wear resistance and low heat build-up progressed effectively, and a carbon black for tire tread rubber, whose selective characteristics were already specified, was proposed (Japanese Patent Application No. 63-182378).

According to the present invention, in addition to adjusting the anisotropy of aggregates by the void volume of aggregates, carbon black having characteristics that the aggregate distribution width is controlled within a certain range is more stable to compounded rubbers and has high wear resistance and low heat buildup. The present inventors have developed the present invention by finding out the fact that they function together.

[Means for Solving the Problems]

That is, the carbon black for tire tread rubber provided by the present invention has a nitrogen adsorption specific surface area (N ₂ SA) of 60.
~ 160m ² / g, DBP oil absorption (DBP) 90 ~ 150ml / 100g belongs to the hard system area, aggregate void volume Vp (ml / g) satisfies the following formula (1) requirements, and centrifugal sedimentation method The aggregate property obtained by the formula satisfies the requirement of the following equation (2) (first invention), or the requirement of the following equations (3) and (4) instead of these equations (1) and (2), respectively. Satisfying the requirements (second invention) is a structural feature.

Vp ≧ 0.00976 × DBP−0.0358 …… (1) ΔDst / (0.601 × st + 4.02) ≦ 1.00… (2) Vp ≦ 0.00976 × DBP−0.1309 …… (3) ΔDst / (0.601 × st + 23.71) ≧ 1.00 (4) However, in equations (2) and (4), ΔDst is the difference between the stroke equivalent diameters of two points, large and small, at which 50% of the maximum frequency in the aggregate Stokes equivalent diameter distribution is obtained, and st is the aggregate The Stokes equivalent diameter (nm) with the highest frequency in the Stokes equivalent diameter distribution.

Of the above-mentioned carbon black characteristic items, the range of particles with a nitrogen adsorption specific surface area (N ₂ SA) of 60 to 160 m ² / g and the structure range of DBP oil absorption (DBP) of 90 to 150 ml / 100 g are the hard type of normal varieties. It is a prerequisite for imparting a high degree of abrasion resistance to compounded rubber. This nitrogen adsorption specific surface area (N ₂ SA) is less than 60m ² / g and DBP oil absorption (DBP) is 90ml
If it is less than / 100 g, it becomes impossible to impart high wear resistance that a tire tread can withstand. Further, when the nitrogen adsorption specific surface area (N ₂ SA) exceeds 160 m ² / g, the dispersion in the rubber component is deteriorated and the wear resistance is hindered from being improved, and at the same time, the heat generation property is increased. On the other hand, DBP oil absorption (DBP) is 150ml / 100g
If it exceeds the range, the ice skid performance is deteriorated, and the viscosity of the rubber is increased, resulting in a disadvantage that the workability is impaired.

Aggregate void volume derived from equation (1) of the first invention
The selective property regarding Vp indicates that the carbon black constituting the present invention has a highly developed and unique aggregate structure, and is characterized by an aggregate morphology having a greater anisotropy than the conventional equivalent varieties. And
If the aggregate void volume Vp satisfies the requirement of equation (1),
It is possible to impart excellent wear resistance to rubber while maintaining the same low heat buildup as when a conventional carbon black compound was used. Carbon black whose aggregate property determined by the centrifugal sedimentation method satisfies the requirement of the formula (2) of the first invention is characterized by a relatively small distribution width (ΔDst) with respect to the Stokes diameter (st) of the aggregate, This property further promotes the increase of wear resistance.

The carbon black satisfying the requirements of the formulas (3) and (4) according to the second invention is opposite to the formulas (1) and (2), and is anisotropy of the aggregate as compared with the conventional equivalent type. Has a small size and has a relatively wide distribution width (ΔDst) with respect to the Stokes diameter (st). Due to this characteristic, high wear resistance equivalent to that of conventional carbon black blended products is maintained. However, it is possible to effectively reduce heat generation.

Each characteristic of carbon black applied to the present invention is based on the following measuring methods.

(1) Nitrogen adsorption specific surface area (N ₂ SA) ASTM D3037-86 “Standard Test Method for Carbon B
According to lack-Surface Area by Nitrogen Adsorption "Method B. The value of IRB # 5 measured by this method is 80.3 m ² / g.

(2) DBP oil absorption (DBP) According to JIS K6221 (1975) “Testing method for carbon black for rubber”, 6.1.2, oil absorption A method.

(3) Aggregate void volume Vp Mercury is pressed into a carbon black sample with a mercury porosimeter to measure the aggregate void diameter, and the cumulative volume of the aggregate void diameter from 0.006 to 7.2μ obtained by the following formula is collected. The collection void volume is Vp.

However, in the above formula, X ₁ is the indicated value (PF) at 25 psi, X ₂
Is the indicated value (PF) at the end point, and CF is a constant determined by the cell. Although the end point of X ₂ differs depending on the sample, in the case of this measurement, when mercury is injected starting from 25 psi, the indicated value will decrease with increasing pressure, but it will appear when the pressure further increases. The value immediately before the pressure point indicating the increase in the indicated value is set as the end point.

(4) st, ΔDst Dry carbon black sample containing a small amount of surfactant 20
Carbon black concentration by mixing with 50% ethanol aqueous solution
Make a dispersion liquid of mg /, and disperse it sufficiently by ultrasonic wave to make a sample. Set the disk centrifuge (Joyes Lobel, UK) at a rotation speed of 8000 rpm, add 10 ml of spin solution (2% glycerin aqueous solution), and then add 1 m.
Inject l of buffer solution (aqueous ethanol solution). Next, 0.5 ml of the sample is added with a syringe and then centrifugal sedimentation is started. At the same time, the recorder is operated to optically generate a distribution curve of the aggregate Stokes equivalent diameter. The Stokes 'equivalent diameter of the maximum frequency in the obtained distribution curve is st (nm), and the difference between the Stokes' equivalent diameters of two large and small points at which a frequency of 50% of the maximum frequency is obtained is ΔDst (nm). AST by this measurement method
M D-24Standard Reference Black C-3 (N-234) st
Is 80 nm and ΔDst is 60 nm.

The carbon black having the characteristics of the first aspect of the present invention has a generating section including a combustion chamber having a combustion burner and a feedstock oil injection nozzle at its head, and a pyrolysis conduit continuous with the combustion chamber.
Using a Y-shaped oil furnace in which a series of pyrolysis conduits of both generation sections converge and associate with the main reaction zone on the cylinder, the carbon black intermediate product gas streams generated in different series are simultaneously fed into the main reaction zone at high speed. It can be manufactured by a method of introducing them and causing them to collide with each other (see Japanese Patent Publication No. 62-10582). At this time, the adjustment of each characteristic is performed by the reaction temperature of formation,
It is carried out by controlling various conditions such as reaction time, combustion gas flow rate and reaction residence time.

The carbon black having the characteristics of the second invention is
Oil having a tangential air supply port on the furnace head, a combustion burner on the air supply port, a combustion chamber in which a raw oil injection nozzle is inserted in the furnace axial direction, and a narrow-diameter reaction chamber connected to the combustion chamber It can be produced by using a furnace and adjusting various conditions such as production reaction temperature, reaction time, combustion gas flow rate, and reaction residence time.

The carbon black of the present invention is blended with an elastomer such as natural rubber, styrene-butadiene rubber, polybutadiene rubber, isoprene rubber, butyl rubber, and various synthetic rubbers and mixed rubbers that can be reinforced with conventional carbon black according to a conventional method. The compounding ratio of carbon black is 30 to 100 parts by weight with respect to 100 parts by weight of the rubber component, and the vulcanizing agent,
A rubber composition for a tire tread is obtained by adding and kneading together with necessary components such as a vulcanization accelerator, an antioxidant, a vulcanization aid, a softening agent and a plasticizer.

[Work]

In the first invention, the carbon black having a large aggregate void volume Vp essentially has an aggregate structure with a well-developed structure and has the function of improving the reinforcing property when compounded with rubber. When Vp satisfies the characteristic requirement of [0.00976 × DBP-0.03581] or more, the significantly developed anisotropic structure acts skillfully, and functions to improve wear resistance while suppressing heat generation. This function is in a state where the distribution width per Stokes diameter of the aggregate is relatively small so that the aggregate property obtained by the centrifugal sedimentation method satisfies the requirement of [ΔDst / (0.601 × st + 4.02) ≦ 1.00]. At times, it is more effectively promoted, and the degree of improvement in wear resistance is increased.

On the other hand, the aggregate void volume V per constant DBP in the second invention
Carbon black that satisfies the requirement that p is less than [0.00976 × DBP-0.1309] has an aggregate structure with small anisotropy and fulfills the function of imparting low heat buildup to the compounded rubber without impairing wear resistance. . This function is [ΔDst / (0.601
× Dst + 23.71 ≧ 1.00] When the distribution width per Stokes diameter satisfying the requirement of [Dst + 23.71 ≧ 1.00] is relatively large, the degree of suppression of exothermicity becomes more prominent, and the degree of suppression of heat generation becomes remarkable.

Nitrogen adsorption specific surface area (N ₂ SA) 60 to 160 m ² / g and DBP oil absorption (DBP) 90
It acts synergistically with the requirement of ~ 150ml / 100g, and exerts the effect of imparting a relatively high level and well-balanced wear resistance and low heat buildup to the rubber component.

〔Example〕

 Hereinafter, examples of the present invention will be described in comparison with comparative examples.

Examples 1 to 3 (first invention), Comparative Examples 1 to 5 (1) Production of carbon black A combustion chamber (inner diameter 400 mm, inner diameter 400 mm, in which a combustion burner and a raw oil injection nozzle are coaxially mounted on the head via a wind box)
Length 800mm, of which cone 200mm) and pyrolysis conduit (inner diameter 60m)
m, length 500 mm) with two series of generation parts in front of the main reaction zone, where the front narrow part with an inner diameter of 90 mm and a length of 700 mm and the rear wide part with an inner diameter of 200 mm and a length of 2000 mm are connected in front of the main reaction zone. An oil-furnace furnace having a Y-shaped structure, which was convergently connected at a degree, was installed. A ring material with a drawing ratio of 0.55 was interposed 50 mm downstream from the intersection at the narrow diameter portion.

Specific gravity (15/4 ℃) 1.0703, viscosity (Engla, 40
/ 20 ℃) 2.10, benzene insoluble matter 0.03%, correlation coefficient (BMC
I) 140, aromatic hydrocarbon oil with an initial boiling point of 103 ° C, and as fuel oil, specific gravity (154 ° C) 0.903, viscosity (CST50 ° C) 16.
1. Hydrocarbon oil with residual coal content of 5.4%, sulfur content of 1.8% and flash point of 96 ℃ was used.

Using the above-mentioned reaction furnace, feedstock oil and fuel oil, the generation conditions shown in Table 1 were applied to produce carbon black (three types) in the characteristic range used in the present invention.

Table 2 shows various characteristics of the carbon black produced under the conditions of Table 1.

The carbon blacks of Comparative Examples 1 to 5 in Table 2 are
Nitrogen adsorption specific surface area (N ₂ SA) and DBP oil absorption amount (DBP) belong to the hard system region within the scope of the present invention, and either or both of aggregate void volume Vp and aggregate property obtained by centrifugal sedimentation method The numerical value of is an example that deviates from the selection characteristic requirement of the present invention.

(2) Rubber compounding Next, each carbon black in Table 2 was compounded in natural rubber in the polymerization ratio shown in Table 3.

Various rubber properties were measured on the rubber composition obtained by vulcanizing the compound of Table 3 at a temperature of 145 ° C. for 40 minutes. The results are shown in Table 4.

Of the rubber characteristics, the amount of wear and loss factor (tan δ)
For the above, the following measuring methods and measuring conditions were used, and the others were in accordance with JIS K6301 "General rubber physical test method".

(1) Abrasion amount 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: grain size 80 mesh, addition amount about 9g
/ min. Relative slip ratio between emery wheel surface and test piece: 60% Test piece rotation speed: 535 rpm Test load: 4 kg In addition, Table 4 shows the wear amount of Comparative Example 1 (0.1241 cc / mi
Abrasion resistance index when n) was 100.

(2) Loss factor (tan δ) Using a Visco Elastic Spectrometer (manufactured by Iwamoto Seisakusho),
The measurement was performed under the following conditions.

Test piece: Thickness 2mm, length 30mm, width 5mm Temperature: Room temperature, Frequency: 50Hz, Dynamic strain rate: ± 1% From the results in Table 4, although the examples of the present invention are superior in wear resistance at the same particle size level as compared with the comparative examples, there is a difference in the loss coefficient (tan δ) which is an index of heat generation. It was found that the balance between the wear resistance and the low heat buildup was significantly improved.

Examples 4 to 7 (second invention), Comparative Examples 6 to 10 (1) Production of carbon black A furnace head was equipped with a tangential air supply port and a combustion burner at the inlet of the tangential air supply port, and a raw material was prepared. Combustion chamber (internal diameter 800 mm, length 700 m) with an oil injection nozzle inserted in the furnace axial direction
m) and a narrow reaction chamber coaxially connected to it (inner diameter 150 m
m, length 120 mm) and the subsequent large diameter reaction chamber were used to produce carbon black by changing the generation conditions. In this case, the same feedstock oil and fuel oil as in Examples 1 to 3 were used.

Table 5 shows the generation conditions, and Table 6 shows the characteristics of the obtained carbon black of the present invention in comparison with Example No., respectively. In addition, Comparative Examples 6 to 10 in Table 6 are examples that deviate from the characteristic requirements of the present invention.

(2) Rubber compounding Next, each carbon black in Table 6 was compounded into natural rubber under the same compounding conditions as in Examples 1 to 3, and the compound was vulcanized at a temperature of 145 ° C for 40 minutes to obtain a rubber composition. It was created.

Various rubber properties of the rubber composition thus prepared were measured, and the results are shown in Table 7. The rubber properties were measured by the same method as in Examples 1 to 3, but the amount of wear was measured in two stages of relative slip ratios of 24% and 60%,
The abrasion resistance index is shown when the wear amount of Comparative Example 6 (slip rate of 24%: 0.0924 cc / min, slip rate of 60%: 0.1098 cc / min) is 100.

The results in Table 7 indicate that the examples of the present invention have significantly reduced loss factors while maintaining wear resistance equal to or higher than that of the comparative examples of opposite particle size levels, and that wear resistance and low heat build-up are high. It is recognized that they are balanced by the level.

〔The invention's effect〕

As described above, the carbon black according to the present invention is capable of imparting a high degree of wear resistance and a low level of heat generation property to a compounded rubber in a relative balance at all times through its special aggregate property.

Therefore, trucks used in harsh driving environments,
As a tread rubber for all kinds of tires including buses, it has the effect of fully satisfying the required performance.

Claims (2)

[Claims] 1. A nitrogen adsorption specific surface area (N ₂ SA) of 60 to 160 m ² /
g, DBP oil absorption (DBP) is 90 to 150 ml / 100 g, it belongs to the hard system area, the aggregate void volume Vp (ml / g) satisfies the requirement of the following formula (1), and the agglomerate obtained by the centrifugal sedimentation method Carbon black for a tire tread whose gate property satisfies the requirement of the following formula (2). Vp ≧ 0.00976 × DBP−0.0358 (1) ΔDst / (0.601 × st + 4.02) ≦ 1.00 (2) However, in the equation (2), ΔDst is 50% of the maximum frequency in the aggregate Stokes equivalent diameter distribution. Large and small 2
The difference between the Stokes equivalent diameters of points, st indicates the Stokes diameter (nm) of the maximum frequency in the aggregate Stokes equivalent diameter distribution. 2. The carbon black for tire tread according to claim 1, wherein the carbon black for tire tread satisfies the requirements of the following expressions (3) and (4) instead of the expressions (1) and (2). Vp ≦ 0.00976 × DBP−0.1309 …… (3) ΔDst / (0.601 × st + 23.71) ≧ 1.00… (4)