JPH0649801B2 - Carbon black for compounding functional parts rubber - Google Patents

Description

TECHNICAL FIELD The present invention relates to carbon black for blending with functional component rubber such as sponge rubber for automobile interiors.

[Conventional technology]

For sponge rubber used for automobile door seals,
It is required that the surface texture be good and the sag (permanent strain phenomenon that occurs when repetitive stress is applied) be small.

Conventionally, as carbon black to be blended with this kind of sponge rubber, FEF class carbon black having a high oil absorption amount,
Alternatively, it is considered effective to blend the above with thermal grade carbon black in an appropriate ratio. The reason for this is that carbon black, which has a high oil absorption function, functions to make bubbles in the rubber uniform and to give an excellent surface skin.
This is because the use of the grade carbon black gives the rubber a reinforcing property, and the incorporation of the thermal grade carbon black contributes to the reduction of the product cost.

In addition to the rubber performance, the product is required to have an appropriate degree of softening, but the compounding of thermal grade carbon black is also effective for the purpose of lowering the rubber hardness.

[Problems to be Solved by the Invention] However, in recent years, as the mass production of automobiles progresses, the above performance requirements including the reduction of raw material cost have become more severe.

Among them, in order to reduce the raw material cost, it is effective to blend a large amount of low-priced and low-priced carbon black, and for this purpose, it is necessary to use a low oil absorption carbon black having a good kneading property. However, carbon black, which has a low oil absorption, has a problem that it is poorly dispersed in rubber, and therefore, consideration of dispersibility is also an important issue.

The present invention has been made for the purpose of addressing the above situation,
Provide carbon black for compounding functional parts rubber that has no sag in rubber products, can impart excellent surface texture and uniform performance with appropriate softness, and has good dispersibility in rubber components To do.

[Means for Solving the Problems]

The carbon black for functional component rubber of the present invention provided to achieve the above object is characterized in that it has the following characteristics.

(1) The mode diameter (st) measured by the centrifugal sedimentation method (DCF method) of aggregates is 150 nm or more.

(2) The ratio (ΔDst / st) of the mode diameter (st) and its half-value width (ΔDst) is 1.05 or more.

(3) The ratio (B / T) of tinting strength (T) and blackness (B) is 1.2 or more.

In order to improve the sag phenomenon of the sponge rubber, it is an important factor that the carbon black to be blended has a large restoring force to the structure and the restoring force to various deformations is uniform. Carbon black with a well-developed structure is required to have a property in which the chain length has been developed, that is, a mode diameter (st) of a certain value or more. In order to equalize the restoring force against deformation, it is desirable to mix chains with various lengths, that is, to make the aggregate distribution width (ΔDst) relatively wide. The mode diameter (st) measured by the centrifugal sedimentation method (DCF method) of aggregates specified in the present invention is 150 or more, and the ratio of the mode diameter (st) to its half-value width (ΔDst) (ΔDst / s
Characteristic items with t) of 1.05 or more are requirements that function to impart this low sag.

A good surface texture of rubber means a state in which the surface is uniformly smooth and has no roughness. In order to obtain such properties, it is effective to reduce the coloring power of carbon black. Further, there is a measure to reduce the oil absorption of carbon black in order to suppress the hardness of rubber to a low level, but it is necessary to reduce the coloring power when a synergistic effect with the improvement of the sag phenomenon is required. . Further, in order to improve the dispersibility of carbon black in rubber, it is usually effective to increase the oil absorption amount, but in the case where a large amount of carbon black is blended in order to lower the unit price of the rubber component,
Rather, it is important to increase the blackness value above a certain value compared to the coloring power of carbon black.

Therefore, the requirement that the ratio (B / T) of the coloring power (T) of the carbon black to the blackness (B) is specified to be 1.2 or more is to give the compounded rubber good surface skin and appropriate softness, and It effectively functions to improve the dispersibility of the components.

As described above, various performances of the functional component rubber targeted by the present invention can be achieved by satisfying the characteristic requirements of the specified three items, and when these requirements are not satisfied, a full performance effect can be obtained. become unable.

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

(1) Aggregate mode diameter (st) and its full width at half maximum (ΔDst)
-: Centrifugal sedimentation method (DCF method) A carbon black sample dried in accordance with JIS K6221 (1982) 5 "How to make a dry sample" is mixed with a 20 vol% ethanol aqueous solution containing a small amount of a surfactant to have a carbon black concentration of 50 mg / The dispersion liquid of is prepared and sufficiently dispersed by ultrasonic waves to prepare a sample. A disk centrifuge (made by Joyes Loebl, UK) was set at a rotation speed of 8000 rpm, 10 ml of a spin solution (2 wt% glycerin aqueous solution at a temperature of 25 ° C) was added, and then 1 ml of a buffer solution (temperature 2).
Inject 20 vol% ethanol aqueous solution at 5 ° C. Next, 0.5 ml of the carbon black dispersion liquid at a temperature of 25 ° C. is injected with a syringe to start centrifugal sedimentation, and at the same time, a recorder is operated to optically create a distribution curve of aggregate Stokes equivalent diameter. The Stokes equivalent diameter of the maximum frequency in the obtained distribution curve is the mode diameter (st), and the difference between the Stokes equivalent diameters of two large and small points at which the frequency of 50% of the maximum frequency is obtained is the half value width (ΔDst), and each is nm. Indicated in units of.

In addition, ASTM D-24 Standard by this measuring method
reference Black C-3 N234 mode diameter (st)
Is 80 nm, and the half width (ΔDst) is 60 nm.

(2) Coloring power In accordance with JIS K6221-82 "Testing method for carbon black for rubber", section 6.1.3, the comparison sample was tested with IRB # 3.
And

(3) Blackness Weigh 0.500 g of a dry carbon black sample with a particle size of 149 μ or less and knead it thoroughly while dropping linseed oil on a glass plate, and then load the paste on a Hoover Mahler 151b.
Knead 25 × 5 times to form a thin film on the surface of the glass plate for measurement. Place the Dencyclon head on the thin film prepared in advance for the reference sample IRB # 2 and set it to 50%, and the meter value when the head is moved at least 3 places is 49.5 to 5
Confirm that it will be 0.5%. In this state, the head is placed on the thin film of sample carbon black, and the meter value is read. The head is moved to 5 places, and the blackness is calculated by the following formula using the average value as the measured value.

Blackness = 50 / T × 100 where 50 is the set value of the reference sample IRB # 2 thin film, T is the measured value of the sample carbon black, and 100 is the reference sample IRB #.
A blackness of 2.

The carbon black of the present invention uses a wide-diameter cylindrical reactor having a drum-shaped throttle portion that gradually converges and opens, and a raw oil is mixed in a high-temperature combustion gas with fuel oil and an appropriate oxidizing agent containing air or oxygen. It is manufactured by introducing atomized air flow in two stages.

Highly aromatic heavy oil such as creosote oil and ethylene bottom oil is used as feedstock, and it is introduced as sufficient fine particle air flow through the atomizing injection nozzle to obtain a good homogeneous mixed state with high temperature combustion gas. To do. As the atomizing injection nozzle, for example, a double cylinder structure having an outer cylinder nozzle that has a water-cooled mantle and is expandable and contractable in the furnace axial direction and an expandable and contractible center shaft nozzle is used. Separately mounted on the furnace head. The feedstock oil is split and introduced in two stages with the atomizing air through the outer cylinder nozzle and the middle cylinder nozzle, but the position of the feedstock oil at this time is changed by the forward and backward movement of the outer cylinder nozzle and the expansion and contraction of the middle cylinder nozzle. be able to.

The carbon black of the present invention can be produced by controlling the amount of air and the amount of fuel oil supplied, the split introduction points of the feedstock oil, the residence time of the produced carbon black in the furnace, etc.

[Action]

The carbon black of the present invention is prepared according to a conventional method together with necessary components such as a vulcanizing agent, a vulcanization accelerator, a softening agent and a foaming agent in EP
It is compounded with rubber components such as DM, but due to the characteristic action of carbon black having a mode diameter (st) of 150 nm and a ratio of the mode diameter (st) to its half-value width (ΔDst) (ΔDst / st) of 1.05 or more, The settling phenomenon is effectively improved.
At the same time, the ratio (B / T) of tinting strength (T) and blackness (B) is 1.20.
The above-mentioned selective characteristics give the rubber proper flexibility, and further function effectively to improve the dispersibility in the rubber, resulting in the formation of a good surface texture.

Such actions synergize to provide the performance required for various functional component rubbers.

〔Example〕

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

Examples 1 to 3 and Comparative Examples 1 to 4 (1) Production of carbon black A combustion box (inner diameter 600 m) in which a wind box provided with a tangential air supply port in the furnace head and the downstream outlet part converge gently
m, length 800 mm) is installed, and a narrow diameter part (inner diameter 400 mm, length 200 mm) that is coaxially connected to the combustion chamber and a taper reaction chamber (inner diameter 800 mm, length 900 mm) that subsequently expands In the oil furnace composed of (1) and (2), a double cylinder structure feedstock atomization injection nozzle was inserted from the furnace head along the furnace center axis, and four combustion burners were installed around it. The atomization injection nozzle for raw material was adjusted so that the upstream raw material oil introduction point (outlet of the outer cylinder nozzle) was located at the convergent portion and the downstream raw material oil introduction point was located at the narrow diameter portion.

By changing the generation conditions using the above-mentioned reactor, the fuel oil combustion rate (C) and the ratio of the fuel oil supply amount per total air supply amount and the upstream side feed oil introduction amount (G) in particular in the Examples are compared.
Was set relatively low to produce carbon black.

As feedstock, specific gravity (15/4 ℃) 1.073, viscosity (Engla 40/20 ℃) 2.10, toluene insoluble content 0.03%, correlation coefficient (BMC
I) 140, aromatic hydrocarbons with an initial boiling point of 103 ° C, and specific gravity (15/4 ° C) 0.903 for fuel oil, viscosity (CST50 ° C) 16.1 and residual carbon content 5.
Hydrocarbon oil with 4%, sulfur content 1.8% and flash point 96 ° C was used.

Table 1 shows the generation conditions, and Table 2 shows the characteristics of the obtained carbon black. Comparative Examples 1 to 3 are examples that deviate from the characteristic requirements of the present invention, and Comparative Example 4 is a commercially available N-741 grade carbon black.

(2) Rubber compounding Next, these carbon black samples were compounded in EPDM at the compounding ratio shown in Table 3.

Various rubber characteristics of the rubber composition obtained by vulcanizing the compound of Table 3 at a temperature of 145 ° C. were measured, and the results are shown in Table 4 in correspondence with each other.

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

Hardness: JIS 6301 5.2A method. However, it was measured with the above formulation except the foaming agent.

Foam rubber specific gravity: By suspension method (the lower ρ, the better the foaming).

Compression set: JIS K6301.

Carve die extrusion evaluation: ASTM D2230 A method.

Surface skin: According to the stage of ASTM D2230 B method.

(3) Evaluation From the results of Table 4, the rubber performances of Examples 1 to 3 of the present invention have moderate flexibility (hardness and modulus are low) as compared with Comparative Examples, and serve as an index for improving sag. It is found that the compression set is reduced and the surface texture is improved.

〔The invention's effect〕

As described above, according to the carbon black of the present invention, even if a large amount of a rubber component is blended, it is possible to always provide high performance with low sag, softness and good surface texture. Therefore, it is effective for sponge rubber products such as door packings for automobile interior parts, weather strips, window frame sealing glass runs, protection moldings, sponge sealing tapes, belt hose cables, ropes, footwear, floats and mat plates.

Claims (1)

[Claims] 1. A carbon black for compounding a functional component rubber having the following characteristics. (1) The mode diameter (st) measured by the centrifugal sedimentation method (DCF method) of aggregates is 150 nm or more. (2) The ratio (ΔDst / st) of the mode diameter (st) and its half-value width (ΔDst) is 1.05 or more. (3) The ratio (B / T) of tinting strength (T) to blackness (B) is 1.20 or more.