JPH0153902B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to carbon black with novel properties that can be blended into various rubbers to provide a relatively high level of hardness while maintaining excellent rebound properties. There are various types of carbon black for rubber compounding depending on their characteristics, and since the characteristics of each type are the main factor that determines the performance of compounded rubber, it is usual to consider the purpose when compounding with rubber components. The method used is to select and use carbon black with variety characteristics that best suit the application. Among these, particle size (or surface area) and structure are typical physical characteristics of carbon black that affect the physical properties of compounded rubber.
Values measured by the nitrogen adsorption method or iodine adsorption method are used as indicators for the latter, the amount of dibutyl phthalate (DBP) adsorption. However, for applications that require the simultaneous provision of contradictory physical properties such as hardness and rebound resilience to compounded rubber, it is virtually impossible to achieve both the required performance using only the representative characteristics of carbon black mentioned above. .
The reason for this is that increases in rubber hardness can be effectively counteracted by selecting a hard type of carbon black with a relatively small particle size or by increasing the blending amount, but on the other hand, in either case, the impact resilience is impaired. This is because carbon black, a soft type that simply has an increased structure, can increase hardness but requires a considerable sacrifice in rebound resilience. The inventors conducted detailed and multifaceted research into the correlation between the colloidal properties of carbon black to be blended and the physical properties of rubber, and found that even carbon black, which belongs to the soft type region with large particle diameters, has a structure. It has been confirmed that if the particle aggregation distribution is high and the agglomeration distribution state of the particles is within a specific selection range, it is possible to impart suitable impact resilience and a relatively high level of hardness to rubber. The present invention provides a new carbon black for rubber compounding developed based on the above knowledge, and its structural features include a nitrogen adsorption specific surface area (N ₂ SA) of 34 m ² /g or less, and a dibutyl phthalate oil absorption. (DBP) 136ml/100g or more and mode diameter of aggregate distribution (Dst) by centrifugal sedimentation method (mμ)
has a selective characteristic that is less than or equal to the value obtained by the formula [0.60 (DBP) - 3.96 (N ₂ SA) + 270]. For each characteristic numerical value of carbon black applied to the present invention, values obtained by the following measuring method are used. (1) Nitrogen adsorption specific surface area (N ₂ SA) ASTM D3037−78 “Standard Methods of
Testing Carbon Black−Surface areaby
Nitrogen Adsorption”, Method C. The N ₂ SA of IRB No. 5 measured by this method is 80.3.
m ² /g. (2) Dibutyl phthalate oil absorption (DBP) Based on oil absorption method A in JIS K6221 (1975) "Testing method for carbon black for rubber" section 6.1.2. (3) Mode diameter of aggregate distribution (Dst) obtained by centrifugal sedimentation method: 20% carbon black containing a small amount of surfactant (dispersion medium), which was dried according to JIS K6221 (1975) 6.2.1.B method and then accurately weighed. Mix it with an aqueous ethanol solution to create a dispersion liquid with a carbon black concentration of 100 mg/ml, and use ultrasonic waves to sufficiently disperse it to use it as a sample liquid.
Disk Seletrifuge Device (UK Joyes)
(manufactured by Loebl) was set at a rotational speed of 6000 rpm, a spin solution (2% glycerin aqueous solution) was added in the range of 10 to 20 ml, and then 1 ml of buffer solution (ethanol aqueous solution) was injected. Next, add sample solution 0.5 to 1.0
ml is injected with a syringe to start centrifugal sedimentation, and at the same time the recorder is activated to photoelectrically separate and record aggregates and record their histograms. The mode diameter is
This is the Stokes equivalent diameter (mμ) of the most frequent frequency (maximum absorbance) in the histogram of the aggregate. Among the above characteristics of the carbon black that constitutes the present invention, the large particle size range with nitrogen adsorption specific surface area (N ₂ SA) of 34 m ² /g or less belongs to the area of soft carbon black of SRF or GPF class, and is suitable for compounded rubber. While it functions effectively to provide suitable rebound, it has a weakening effect on hardness. In addition to the above-mentioned prerequisite properties, the carbon black of the present invention has a dibutyl phthalate oil absorption (DBP) of 136 ml/100 g or more and a mode diameter (mμ) of aggregate distribution (Dst) determined by centrifugal sedimentation method [0.6 (DBP) - 3.96 (N ₂ SA) +
270], and by satisfying these property requirements, it is possible to impart a high level of rubber elasticity to compounded rubber in a relatively high hardness range, which was previously considered extremely difficult. becomes.
In this case, when N ₂ SA exceeds 34 m ² /g, the drop in rebound becomes large, DBP falls below 136 ml / 100 g, and Dst mode diameter becomes [0.60 (DBP) - 3.96
(N ₂ SA) + 270], the increase in hardness decreases relatively, making it impossible to achieve any of the objectives. Although the reason for this has not yet been elucidated, the identified Dst mode diameter is lower at the N ₂ SA and DBP levels compared to conventional products, and the aggregate secondary particles (Aggregate) are relatively small. Because it is concentrated in the region, the proportion of coarse aggregates that originally lack stability in the rubber and have a negative effect on hardness and rubber elasticity is significantly reduced, and the unique colloidal properties of the rubber are low. _{2 This} is because it promotes the impact resilience improvement effect based on SA, suppresses the decrease in hardness due to low N ₂ SA, and works effectively to increase hardness at a relatively high level in conjunction with the effect of high DBP. Guessed. The carbon black of the present invention is produced by using a wide-diameter cylindrical reactor with a drum-shaped constriction that slowly converges and expands. It is produced by introducing atomizing airflow into two stages. Highly aromatic heavy oil such as creosote oil or ethylene bottom oil is used as the feedstock oil, and a sufficient fine particle airflow is generated through the atomization injection nozzle to obtain a highly homogeneous mixture with the high temperature combustion gas. will be introduced.
The atomization injection nozzle used is, for example, a double-tube structure consisting of an outer cylinder nozzle with a water-cooled jacket that can move forward and backward in the direction of the furnace axis, and a telescopic central cylinder nozzle inserted into the outer cylinder nozzle. It is attached separately to the furnace head. 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. Using the above device, carbon black with the desired N ₂ SA and DBP is produced by adjusting the ratio of the total amount of air supplied to the total amount of raw fuel oil introduced and the amount of reaction additive in the usual manner. The oil combustion rate is maintained at 170% or less, the flow rate of combustion gas at the upstream feed oil introduction position is maintained at 60 to 120 m/sec, and the residence time of reaction product gas in the furnace is maintained at 500 to 700 milliseconds. Particle carbon black generation conditions (fuel oil combustion rate of 200% or more, combustion gas flow rate of 10 m/
By setting characteristic conditions different from the reaction product gas residence time in the furnace (900 to 1100 milliseconds), the low Dst mode diameter characteristics specified in the present invention are imparted. The carbon black according to the present invention is blended into various rubber components with necessary components such as a vulcanizing agent, a vulcanization accelerator, an anti-aging agent, a vulcanization aid, a softener, and a plasticizer by a conventional method. The rubber composition has both excellent rebound properties and a relatively high level of hardness. Therefore, it is extremely useful for tire cases, coating rubber for steel breakers, and other tire and rubber industrial parts that require a high degree of stiffness and elasticity. Hereinafter, the present invention will be explained based on examples. Example Combustion chamber (inner diameter
A tapered reaction zone (length: 700mm, length: 1000mm) is expanded through a narrow diameter section with an inner diameter of 250mm and a length of 200mm.
It has a cylindrical structure lined with refractory bricks with a continuous length of 9,000 mm, and is equipped with a wind box with tangential air supply ports at the furnace head, and a repositionable quench nozzle in the downstream area of the rear reaction chamber. In the reactor, 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 was adjusted so that the upstream raw material oil introduction point (the jet hole of the outer cylinder nozzle) was located at the convergence region, and the downstream raw material oil introduction point was located at the narrow diameter region. Carbon black was produced using the above reactor and applying the generation conditions shown in the table. The fuel oil used is a hydrocarbon oil with a specific gravity (15/4℃) of 0.903, a viscosity (CST50℃) of 16.1, a residual coal content of 5.4%, a sulfur content of 1.8%, and a flash point of 96℃. 4℃) 1.0703, viscosity (Engler, 40/20
A highly aromatic hydrocarbon oil with a benzene insoluble content of 0.03%, a correlation coefficient (BMCI) of 140, and an initial boiling point of 103°C was used.

【table】

[Table] Table notes:
*〓SEAST SO〓〓Made by Tokai Carbon Co., Ltd.〓
**〓SEAST V〓〓Made by Tokai Carbon Co., Ltd.〓
Run Nos. 4 to 6 did not meet the characteristic requirements of the present invention. Next, the various carbon black samples listed in the table were blended with the natural rubber component and the synthetic rubber component at the blending ratios shown in the table.

【table】

[Table] Table note: * Manufactured by Japan Synthetic Rubber Co., Ltd. Various rubber properties were measured for rubber compositions obtained by vulcanizing the compounds shown in the table at a temperature of 145°C. The results are shown in the table in correspondence with the carbon black samples shown in the table.

【table】

[Table] From the results in the table, the rubber compositions (Run Nos. 1 to 3) containing the carbon black of the present invention are FEF
It has been found that it has a hardness equivalent to that of (M550) grade carbon black compounded rubber and an impact resiliency similar to that of GPF (N660) grade carbon black compounded rubber, and other rubber physical properties are also good. In addition, a carbon black compounding comparative example (Run
In Nos. 4 to 6), it was not possible to improve both hardness and rebound resilience.

Claims (1)

[Claims] 1. Nitrogen adsorption specific surface area (N ₂ SA) 34 m ² /g or less,
Dibutyl phthalate oil absorption (DBP) 136ml/100
g or more and the mode diameter (mμ) of aggregate distribution (Dst) by centrifugal sedimentation method is [0.60 (DBP) − 3.96
(N ₂ SA) + 270] Carbon black for rubber compounding that has selective properties less than the value obtained by the formula.