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What is Pigment Carbon Black?

What is Pigment Carbon Black?

Carbon black as pigment that used in coatings & paints, inks, plastics and etc is called pigment carbon black. Pigment carbon black can also provide function of conductivity, electrostatic shielding, shielding against UV, preventing resin’ aging in application for coatings & paints, inks, plastics. Hence, in a broad sense pigment carbon black is called special carbon black (as distinguished from carbon black that used in rubber).

According to the forecast and appraisal of Notch Group in the USA, the productive capacity of carbon black in the world in 2007 is 10.16 million tons and it can grow to more than 12 million tons in 2012. 90% are carbon black for use in tire and rubber industry. The rest part about 10% is used as pigment.

Characteristics of Pigment Carbon Black 

1. Comparing with other pigment, carbon black is better in tinting strength and hiding power.

2. Comparing with other pigment, carbon black is good in durability on heat, chemicals and light.

3. Carbon black is difficult to disperse stably in the organic resin system because its particle size only ranges from a few nanometers to dozens of nanometers, and porosity reaches 90%, moreover, it is inorganic materials. However, carbon black after strict control and treated with special craft can be well dispersed in paints, inks and plastic system. 

4. Comparing with rubber carbon black, pigment carbon black has higher and more specific requirements in blackness,tinting strength,surface activity,conductivity,ash,light transmittance of toluene,dispersibility,fluidity and other technical indexes.

Technical Crafts (Processing Methods) of Pigment Carbon Black 

Generally speaking, the processing methods for pigment carbon blacks globally are Furnace, Touching (including Channel and Gas without channel) and Thermal Decomposition. We are now using furnace method and gas method, which are the most important and conventional crafts currently.

1. For Furnace processing, in a hermetic furnace, taking gaseous hydrocarbon (natural gas) or liquid hydrocarbons (coal tar or anthracene oil) as raw material with right amount of air, forming airtight turbulence system in the reacting furnace for oxidation and thermal decomposition under high temperature to produce carbon black (we could control performance of pigment carbon blacks by controlling flame quenching). Then, the pigment carbon black products are separated from the quenched gas steam through filtering system after cooling. The character of furnace method is a wide range of choices of its raw materials with various performance of pigment carbon black. 

The use of gaseous hydrogen as the main raw material is called gas-furnace method while the use of liquid hydrogen as the main raw materials is called oil-furnace method.

In contrast with other processes of carbon black, oil-furnace method carbon black is characterized by many technical device,various performance of carbon black,high unit productivity,high utilization rate of thermal energy,low consumption of raw material and comprehensive energy,low cost and so on. Therefore oil-furnace has already been the leading method and more than 95% of carbon black in the world is produced by application of the oil-furnace method.

2. For channel method, after gasified in a gasification chamber, solid hydrocarbons (crude anthracene) or liquid hydrocarbons (anthracene oil) are mixed with combustive gas (usually natural gas, sometimes coke gas and water gas). As feedstock, they are directed through a circular pipe to the heating room of natural ventilation, incompletely burned under high temperature in thousands of china flame nozzles under channel steel with formation of fishtail diffusion flame. During burning, the reduction layer of flame keeps touching the channel steel with slow reciprocating motion, which makes carbon black formed by pyrolysis deposit on the surface of channel steel and later be collected after cooled down in the cooling side of the device’s wall. While the cooling in the heating room without channel steel is called gas method. The carbon blacks obtaining smaller particle size under the improved method by which has relatively lower output than furnace process perform better in blackness and tinting strength. 

Gas without channel method is improved technical craft of channel method without channel, collecting only suspension of carbon black in the smoke. In contrast with channel method, Gas without channel method has good productivity. But in virtue of no channel, the control ob flame is inferior to those of channel method or drum drawing method, which causes weaker jetness of manufactured carbon black.

Powder Form and Bead Form of Carbon Black

Pigment carbon black has two physical existing forms: powder form and bead form. Powder form is easy to disperse but with high transport cost and is apt to cause environmental pollution while using. Bead form is convenient to transport due to low dust pollution and high density, but is difficult to disperse by comparison with powder form.