JPH0641540B2 - Carbon black for tire tread rubber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a carbon black for a tire tread rubber, which can be blended with a rubber component to provide good wear resistance and relatively significantly low exothermicity. Regarding

[Conventional technology]

It has been conventionally considered that the specific surface area (particle diameter) and the structure of the reinforcing performance of rubber with carbon black are the dominant factors, and there are various types according to the characteristics of the rubber. When blending with the rubber component, carbon black having a variety of characteristics suitable for the intended member is selectively used. For example, for rubber members that require a high degree of wear resistance under severe driving conditions such as tire treads,
Hard carbon black such as N110 and N220 is applied.

However, in recent years, due to the severer tire running, the performance required for the tire tread has become more sophisticated, and it is particularly important to have both high wear resistance and low heat buildup.

Generally, the larger the specific surface area and the structure of carbon black, the more the abrasion resistance increases, but on the other hand, the heat generation property increases, and both characteristics have a trade-off relationship. Therefore, it is extremely difficult to impart high abrasion resistance and low heat buildup to the rubber composition at the same time.

In order to solve this problem, various attempts to apply carbon black having specific properties have been proposed (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 retain wear resistance and heat buildup at good levels, and further improvement is desired. Has been done.

The present invention has conducted research from a different angle from the prior art for the purpose of solving the above-mentioned problems, and as a result, a carbon black rubber having relatively small aggregate voids in an aggregate having a constant structure level is used as a rubber component. It was developed based on the knowledge that anti-rubber performance (having both high abrasion resistance and low heat build-up) effectively progresses when compounded in.

[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 to 160 m ² / g and a DBP oil absorption of 90 to 150 m / 100 g belong to the hard system region, and the aggregate void volume Vp (m /
g) has a selective characteristic equal to or less than the value calculated by the formula [0.00976 × DBP oil absorption-0.1309].

Among the characteristic items of the above carbon black, the range of particles having a nitrogen adsorption specific surface area (N ₂ SA) of 60 to 160 m ² / g and DB
The structure range with a P oil absorption of 90 to 150 m / 100 g belongs to the hard region of a normal product and is a prerequisite for imparting a high degree of abrasion resistance to the compounded rubber. When the nitrogen adsorption specific surface area (N ₂ SA) is less than 60 m ² / g and the DBP oil absorption amount is less than 90 m / 100 g, it becomes impossible to impart high wear resistance that the 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 abrasion resistance is hindered from being improved, and at the same time, the exothermic property is increased. On the other hand, the DBP oil absorption is
If it exceeds 150 m / 100 g, the ice skid performance is deteriorated, which is not preferable.

[0.00976 × DBP oil absorption-0.1309] The selective property regarding the aggregate void volume Vp (m / g) derived from the formula is that the carbon black constituting the present invention has a small pore volume between aggregates, in other words. It is characterized by having smaller anisotropy than the conventional equivalent carbon black.

And, carbon black in which the aggregate void volume Vp (m / g) is less than or equal to the value calculated by the above formula, the anisotropy is small and the unique aggregate structure efficiently interacts with the rubber component during the compounding process. Performs the function of improving, and through this action, imparts a relatively low level of heat generation while maintaining the same wear resistance as when blending conventional types of carbon black with a nitrogen adsorption specific surface area and DBP oil absorption at the same level. It becomes possible to do.

Each characteristic value of carbon black applied to the present invention is a value obtained by the following measuring method.

(1) a nitrogen adsorption specific surface area _{(N 2 SA) ASTM D3037-78 "} Standard Methods of Te
sting Carbon Black Surface Area by Nitrogen Adsorp
tion ”by Methed B.

IRB # 5 nitrogen adsorption specific surface area (N
₂ SA) is 80.3 m ² / g.

(2) DBP oil absorption amount It is the value obtained by the oil absorption amount A method of JIS K6221 (1975) "Testing method of carbon black for rubber", 6.1.2.

(3) Aggregate void volume Vp (m / g) A mercury porosimeter (Micromeritics Co., Ltd.) was used as a sample of carbon black (granulated product having a particle size of 250 to 500 μm) dried according to JIS K6221 (1985) “How to prepare a dried sample”. Manufactured by PORE SIZER 9300) to measure the pore size of the aggregate, and obtain the aggregate void size of 0.006 ~
The volume of different volume of the void diameter up to 7.2μ is defined as the aggregate void volume Vp.

However, in the above formula, X ₁ is the indicated value (PF) at 25 psi,
X ₂ is the end point reading (pF), X ₂ is the end point 30,000 psi reading (pF), CF is a constant determined by the cell, and W is the weight of the carbon black sample. Note that p
F (unit: picofarad) is a value indicated as the capacitance between the mercury inside the cell of the device and the electrode outside the cell, and the amount of press-fitted mercury is calculated from the change in this capacitance.

The carbon black having these characteristics is provided with two series of generating units each including a combustion chamber having a combustion burner and a raw oil injection nozzle at its head and a pyrolysis conduit continuous with the combustion chamber. A method of using a Y-shaped oil-furnace furnace with a conduit converging and converging in a cylindrical main reaction zone, simultaneously introducing high-speed carbon black intermediate product gas streams into the main reaction zone at the same time to cause mutual collision (special It can be produced according to Kosho 62-10581).

At this time, the aggregate void volume Vp is adjusted mainly by changing the total air supply amount, the fuel oil supply amount, the fuel combustion rate, and the feedstock oil introduction amount as operating conditions in the generation part series, and also by adjusting the nitrogen adsorption specific surface area. The adjustment of (N ₂ SA) and DBP oil absorption is performed mainly by controlling the combustion conditions in the furnace, the residence time in the furnace of the produced carbon black flow, and the like. It is blended with elastomers such as butadiene rubber, polybutadiene rubber, isoprene rubber, butyl rubber, various synthetic rubbers that can be reinforced with commonly used carbon black, and mixed rubbers. The compounding ratio of carbon black is 10 rubber components.
A rubber for a tire tread by mixing and kneading with necessary components such as a vulcanizing agent, a vulcanization accelerator, an antiaging agent, a vulcanization aid, a softening agent and a plasticizer in a proportion of 35 to 100 parts by weight relative to 0 parts by weight. Obtain the composition.

[Action]

Carbon black having a small aggregate void volume Vp essentially has an aggregate structure in which the development of the structure is suppressed, and has the function of lowering the heat generation property when compounded with rubber, but especially this aggregate void volume Vp is 〔0.0097
When the characteristic requirement of 6 × DBP oil absorption-0.1309] value or less is satisfied, the anisotropy of carbon black becomes small, and this action remarkably lowers the heat buildup of the rubber component. This function is based on the premise that the nitrogen adsorption specific surface area (N ₂ SA) 60
~ 160m ² / g and DBP oil absorption 90 ~ 150m / 100g synergistically work to realize effective low heat buildup without damaging good wear resistance to rubber component To do.

〔Example〕

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

(1) Manufacture of carbon black A combustion chamber (inner diameter 400m
m, length 800 mm, cone part 200 mm of this, and two series of generators equipped with pyrolysis conduit (inner diameter 60 mm, length 600 mm)
A Y-shaped oil furnace with a Y-shaped converging connection at a crossing angle of 60 ° in front of the main reaction zone in which a rear wide diameter part with an inner diameter of 200 mm and a length of 2000 mm and a front narrow part with an inner diameter of 90 mm and a length of 900 mm are connected in series installed. A ring member having a drawing ratio of 0.90 was provided 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 (BM
GI) 140, aromatic hydrocarbon oil with an initial boiling point of 103 ° C, and specific gravity (154 ° C) 0.903 as fuel oil, viscosity (CST50
℃) 16.1, hydrocarbon content 5.4%, sulfur content 1.8%, flash point 96 ℃ hydrocarbon oil was used.

Using the above reaction furnace, feedstock oil, and fuel oil, the generation conditions shown in Table I were applied to produce carbon black (4 types) in the characteristic range used in the present invention.

Table II shows the nitrogen adsorption specific surface area (N ₂ SA), DBP oil absorption amount, aggregate void volume Vp, and [0.00976 × DBP oil absorption amount-0.1309] of each carbon black produced under the conditions shown in Table I. It was

In addition, Run NO. 5-8 shown as a comparative example in Table II
Is a nitrogen adsorption specific surface area (N ₂
SA) hard carbon black of 60 m ² / g or more, all of which have an aggregate void volume Vp outside the requirements of the present invention.

(3) Rubber compounding Next, the various carbon blacks in Table II were compounded in the natural rubber in the compounding ratios shown in Table III.

Various rubber properties were measured on the rubber composition obtained by vulcanizing the compound of Table III at a temperature of 145 ° C. for 40 minutes. The results are shown in Table II.
Corresponding to the compounding carbon black Run NO.

The rubber characteristic measuring method and measuring conditions were as follows.

(1) Wear amount Using a Lambourn wear tester (mechanical slip mechanism),
The measurement was performed under the following conditions.

Test piece: thickness 10 mm, outer diameter 44 mm Emery wheel: GC type, grain size 80, hardness H added carbon random powder: grain size 80 #, addition amount about 9 g / min Relative slip ratio between emery wheel surface and test piece: 24%,
60% Test piece rotation speed: 535 rpm Test load: 4Kg (2) tan δ Visco Elastic Spectrometer (manufactured by Iwamoto Seisakusho)
The measurement was performed under the following conditions.

Test piece: Thickness 2 mm, length 30 mm, width 5 mm Temperature: Room temperature Frequency: 50 Hz Dynamic strain rate: ± 1% (3) Others All JIS K6301 "general rubber physical test method".

From the results of Table IV, the rubber composition according to the example in which the carbon black satisfying the carbon black characteristic requirements of the present invention was blended, the aggregate void volume was in accordance with the comparative example in which the carbon black not satisfying the relational expression value of the present invention was blended. It is recognized that the loss coefficient (tan δ), which is an index of exothermicity, is significantly reduced while maintaining the same level of wear resistance at the same nitrogen adsorption specific surface area level as compared with the rubber composition.

[Effects of the Invention] As described above, the carbon black according to the present invention has an aggregate structure with small anisotropy in which the development of the structure is suppressed, and has good abrasion resistance and relative relative to the compounded rubber. It is possible to impart extremely low heat generation property to the same time. Therefore, when it is blended with a tread rubber for a tire for a passenger, which is particularly required to have low fuel consumption, it is useful enough to satisfy the required performance.

Claims (1)

[Claims] 1. A nitrogen adsorption specific surface area (N ₂ SA) of 60 to 160 m ^2.
/ G, the DBP oil absorption amount is 90 to 150 m / 100 g, belongs to the hard system region, and the aggregate void volume Vp (m / g) is [0.
6 × DBP oil absorption-0.1309] A carbon black for a tire tread rubber having a selective characteristic equal to or less than a value calculated by the formula.