JPS5846259B2 - Carbon black for tire rubber compounding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to carbon blacks for use in automobile tire rubber formulations that are effective in imparting a high degree of dynamic and reinforcing properties to the rubber.

In recent years, there has been a strong demand for the development of fuel-efficient tires in response to the energy-saving trend, and a variety of research is being carried out on rubber materials.

Improving the fuel efficiency of tires is achieved primarily by reducing the rolling resistance during driving, but this is achieved by giving the rubber material dynamic properties that suppress loss of driving energy, such as low heat build-up and high rebound resilience. It is said that this is effective.

In order to improve these dynamic rubber properties from the viewpoint of the properties of the carbon black to be blended, it is preferable to use a soft variety with a particle size as large as possible and a wide particle size distribution.

However, carbon black belonging to the soft type region exhibits the opposite tendency in terms of imparting reinforcing properties, resulting in deterioration of rubber performance such as tensile strength and abrasion resistance.

As a result of detailed and multifaceted research on the correlation between the properties of the carbon black to be blended and the rubber performance obtained, the inventors found that even if the particle size of carbon black falls within the soft range, It was confirmed that if the colloidal properties, which are related to agglomeration and distribution states and their physicochemical properties, have specific selective properties, it is possible to make rubber have both high dynamic properties and reinforcing properties at the same time. .

The present invention was made based on the above findings, and the characteristics of the provided carbon black are that the average particle diameter (dn) under an electron microscope is 34yxμ or more, and the amount of iodine is 40 to 60r.
v/1, DBP oil absorption 95-130rILl/100r
It has a characteristic area of
) has a selective characteristic that exceeds the value obtained by the formula.

For each characteristic numerical value of the above-mentioned carbon black, the value obtained by the following measuring method is applied.

(1) The average particle diameter (dn) of carbon black was sampled using an electron microscope using an ultrasonic cleaning method at a frequency of 28 and fG (
After dispersing in chloroform for 30 minutes at has been done.

]. This was directly photographed with an electron microscope at a magnification of 20,000 times and a total magnification of 80,000 to 100,000 times, and the diameters of 1,000 carbon black particles were randomly measured from the obtained photograph to create a 377 Lμ segmented histogram. The arithmetic mean particle diameter (dn) is determined from

(2) Iodine adsorption amount JIS K6221 (1975) “Testing method for carbon black for rubber Complies with the method in Section J6.1.1.

(3) DBP oil absorption JIS K6221 (1975) Test method for carbon black for rubber” 6.1.2.

(4) Coloring power dry carbon black sample 0.1000f (±0.00
02f? ), zinc white 3,000P, linseed oil I, 50m
Add 1 and use a two-piece set of mallers to add 9 (
Knead (15 pounds) for 12,525 revolutions (25 revolutions, repeat 5 times) to create a paste.

The paste was then spread to a certain thickness on a glass plate using a film applicator (0,002 inch).
A reflectance photometer (Denjikron, Welch 5 Scientific Co., Ltd.) was adjusted so that the reflectance of the paste from which the reference carbon black sample was prepared was 50.
A9115, reflection head +=3832A) is used to measure the reflectance (T) of the sample carbon black paste, and the tinting power (poly) is calculated using the following formula.

Coloring power of sample carbon black (correspondence) - 50/TX [Coloring power of standard carbon black (coloring power of standard carbon black, standard carbon black, electron microscope average particle diameter (dn) approximately 8071 Lμ, D
A series of reference carbon blacks with a relatively wide range of coloring power are defined, with 1 Sterling S'' (SRF) having a BP oil absorption of 65 to 7011 Ll/1001 as 100 excellent,
The tinting power of the sample carbon black is measured using a reference carbon black that has a tinting strength as close as possible to that of the sample carbon black.

I RB (Industry
Reference Black) The coloring strength of Nt13 is 208%.

(5) Compressed DBP oil absorption ASTM D3493-79” CARBON BLA-
CKDIBUTYL PHTHALATE ABSOR
P-TION NUMB DROF COMPRESSE
By DSAMPLE.

Among the characteristics of the carbon black constituting the present invention, the electron microscope average particle diameter (dn) is 34 mμ or more, the iodine adsorption amount is 40 to 60 rIuil/1, and the DBP oil absorption is 95 to 1.
30m1/100f? This range belongs to the area of FEF (N550) grade soft carbon black, which is usually blended into rubber components used in tire carcass, sidewall parts, etc.
While it is effective in imparting suitable low heat generation properties to compounded rubber, it is ineffective in imparting reinforcing properties.

In addition to the above-mentioned prerequisite properties, the carbon black of the present invention has a coloring power of 170% or more and a compressed DBP oil absorption of CO,5
5 (DBP oil absorption) + 31.0] has selective properties that exceed the value obtained by the formula, and by satisfying all of these property requirements, the compounded rubber can have a high degree of dynamic and reinforcing properties. becomes possible.

Coloring power is a measure that optically grasps the particle physical properties mainly based on the morphological structure factors of straftia, such as the size and distribution of the basic particles of carbon black, and the primary and secondary agglomeration properties of the basic particles. When this value is high, the above-mentioned particle physical properties form properties suitable for improving rubber reinforcing properties, and become a contributing factor to increasing rubber performance such as tensile strength, shear stress, and abrasion resistance.

However, when the tinting power is less than 170%, effective reinforcing properties cannot be imparted in relation to other property items.

The compressed DBP oil absorption is an index for evaluating the skeletal structural characteristics of carbon black mainly composed of primary straphthiae.

The formation of straphthia is caused by a phenomenon in which fine particles of oil droplets repeatedly collide with each other in the initial stage of carbon black production (skeletal agglomeration form) through the thermal decomposition reaction process of raw material hydrocarbons, and in the latter stage of reaction production, the agglomerated particles It is assumed that this phenomenon is based on the entanglement and fusion of bodies (secondary aggregation form), but since the aggregates that are formed have structural strengths and weaknesses, they can be classified into non-destructive structures. The form is primary straftia, which is distinguished from the secondary straftia, which has a deformable/destructive structural form.

The DBP oil absorption amount determined by the measurement method in Section 6.1.2 of JIS K6221 (1975) is understood as an overall straphthia index that includes both the above-mentioned first-order structuring and second-order structuring.

Therefore, the compressed DBP oil absorption amount is (” 0.55 (D
BP oil absorption)+31.0) or more means that the non-destructive primary straphthia in the total straphthia
It exhibits an agglomerated structure in which a large proportion of is contained above a certain value, and this structural characteristic strengthens the mutual adhesion with the compounded rubber, and prevents phenomena such as internal friction, cohesive fatigue, and shear fracture due to high loads and repeated deformation. It functions both to suppress heat generation and increase reinforcing properties.

In addition, increasing the coloring power narrows the width of the particle size distribution and causes an increase in heat generation, but the high level of compressed DBP oil absorption characteristics sufficiently compensates for this tendency to deteriorate due to heat generation.

Carbon black with the above characteristics is produced by burning fuel oil and air or an appropriate oxidizing agent containing oxygen in a cylindrical reactor with a venturi-like narrow diameter region. It is produced by introducing an atomizing air stream of raw material oil into two stages.

The flow rate of the combustion gas can be continuously varied by passing the combustion gas flow through the venturi-like narrow diameter region.

The feedstock oil is selected from highly aromatic heavy oils such as creosote oil and ethylene bottom oil, and is injected in the state of sufficient fine particle airflow through the atomization injection nozzle to obtain a high degree of homogeneous mixing with the hot combustion gas. Introduce.

For example, the atomization injection nozzle has a double-tube structure consisting of an outer cylinder nozzle that has each water-cooled jacket and can move forward and backward in the direction of the furnace axis, and a middle cylinder nozzle that is inserted into the outer cylinder nozzle and can extend and retract. It is attached to the furnace head separately from the burner.

The raw material oil is introduced in two stages along with atomizing air through the outer tube nozzle and the center tube nozzle, but the feedstock oil introduction position can be changed as appropriate by advancing and retracting the outer tube nozzle and expanding and contracting the center tube nozzle. can.

The most preferable feedstock introduction conditions are to set the introduction position at the convergence part of the Venturi reaction zone on the upstream side and the narrowest rear part on the downstream side, and set the introduction ratio to 6 of the total feedstock oil supply amount on the downstream side.
It is introduced in an amount of 5 to 90 q6, preferably 65 to 77 q6.

In addition, the combustion rate of fuel oil is in the range of 150 to 230%,
The flow velocity of combustion gas at the downstream raw material introduction point is set to 90 m/
The carbon black characteristics specified in the present invention can be imparted by providing various conditions such as maintaining the residence time of the reaction product gas in the furnace at 300 milliseconds or less, preferably at least 250 m7 seconds.

The carbon black according to the present invention can be prepared by adding a vulcanizing agent and
It is blended into various rubber components together with necessary ingredients such as vulcanization accelerators, anti-aging agents, vulcanization aids, softeners, and plasticizers, but the resulting rubber composition is softer than conventional FEF (N550) grade. It has the same low heat build-up and high rebound properties as when compounded with carbon black, and also has advanced reinforcing performance such as tensile strength, tear strength, and abrasion resistance comparable to when compounded with HAF (N330) grade bird carbon black. .

As described above, the carbon black provided by the present invention has the effect of simultaneously satisfying the dynamic properties and reinforcing properties required for fuel-efficient tires when blended with rubber. It is extremely suitable for compounding tire rubber such as tread.

Example Combustion chamber (inner diameter 600m71L, length 600mm) and rear reaction chamber (inner diameter 500mm, length 5400mm) are connected via a venturi-shaped main reaction chamber (length 2000myz, narrowest diameter part 150mm inner diameter) The reactor has a cylindrical structure lined with refractory bricks, and is equipped with a wind box equipped with a tangential air supply port at the head of the reactor, and a quench nozzle that can be repositioned downstream of the rear reaction chamber. In,
A raw material oil atomization injection nozzle with a double-tube nozzle structure was inserted from the furnace head along the central axis of the furnace, and four combustion burners were installed coaxially around it.

The raw material oil atomization injection nozzle is adjusted so that the upstream raw material introduction point (the jet hole of the outer cylinder nozzle) is located at the convergence part of the venturi-shaped main reaction chamber, and the downstream raw material introduction point is adjusted so that the central cylinder nozzle is extended. It was adjusted so that it was located at the narrowest rear part of the main reaction chamber.

Carbon black was produced using the above reactor and applying the generation conditions shown in Table I.

Fuel oil has a specific gravity (15/4℃) of 0.903 and a viscosity (C
8T50℃) 16.1, residual coal content 5.1 or more, sulfur content 1.8
General heavy hydrocarbons with a flash point of 96°C are used as feedstock oil, specific gravity (15/4°C) 1.073, viscosity (Engler-40/20°C) 2.101, penzene insoluble content 0.0.
3%, correlation coefficient (BMCI) 140, initial boiling point 103°C
aromatic hydrocarbons were used.

Table H shows the properties of each manufactured carbon black, commercially available FEF (N550) and HAF Nakamoto (N35).
The characteristics of 1) grade carbon black and IRB=#=4 carbon black sample are shown in comparison.

RunNa3 and RunNa6 did not meet the characteristic requirements of the present invention.

Next, the various carbon black samples shown in Table H were blended with the natural rubber component and the synthetic rubber component at the blending ratios shown in Table 2.

The results of measuring various rubber properties of the rubber composition obtained by vulcanizing the compound in Table (1) at a temperature of 145° C. for 40 minutes are shown in Table (2) in correspondence with the carbon black testing in Table H.

Among various rubber properties, the amount of wear was measured using a Lambourn abrasion tester (mechanical slip mechanism) under the following conditions.

Test piece: thickness 107n1rL1 outer diameter 44cm, emery wheel 20C type, hardness H1 particle size 80. Added carborundum powder particle size 80 mesh, amount added 9? /min, Relative slip rate with emery wheel surface: 12q6, Test piece rotation speed: 660 rprJ Test piece load: 4 to 9 The degree of heat generation was measured using a Gudrich flexometer according to the ASTM D623-67A method.

All other rubber properties are based on JISK6301.
1i "General Rubber Test Method".

From the results in Table 2, the rubber compositions (Runs 1 to 4) containing the carbon black of the present invention have dynamic properties and H
It has been found that it has reinforcing properties comparable to AF (N351) grade Bird carbon black compound rubber.

Incidentally, RunNch 5 and 6 are comparative examples of carbon black formulations that do not meet the characteristic requirements of the present invention, and in this case, it was not possible to improve both dynamic characteristics and reinforcing characteristics.

Claims (1)

[Claims] 1 Electron microscope average particle diameter (dn) 34yxμ or more,
Iodine number 40~60/f, DBP oil absorption 95~1
It has a characteristic area of 30d/100S' and a tinting power of 17
0% or more and compressed DBP oil absorption (0,55 (DBP
Carbon black for tire rubber compounding that has selective properties that exceed the value obtained by the formula (oil absorption amount) + 31.0).