Study On The Oxidation Process Of Carbon Black And Preparation Of Water Paste With Oxidized Carbon Black

As a kind of black pigment,carbon black is widely used in coatings,colorants,printing and dyeing industry with the advantages of high tinting strength,good stability and low cost.However,because of the small size,large specific surface area and high potential energy,the carbon black particles are easy to aggregate into large particles,So it is difficult to disperse stably in the water system.From the point of view of environmental protection,water system is the trend of development.Therefore,it is necessary to improve the dispersion of carbon black in aqueous system by post-treatment oxidation.This paper mainly studies the liquid phase oxidation and gas phase oxidation,as well as the dispersion of carbon black in color paste after oxidation.Firstly,the two methods of liquid phase and gas phase oxidation were compared.Two kinds of oxidants nitric acid and hydrogen peroxide in liquid phase oxidation were compared.The experimental results showed that the pH value of carbon black decreased and the volatility of carbon black increased,with the oxidation of nitric acid and hydrogen peroxide.The results of IR spectra show that the oxidized carbon black surface contains oxygen-containing functional groups.The XRD results show that the liquid phase oxidation process does not change the crystallite structure of carbon black.As for the degree of oxidation,the ability of nitric acid solution is higher than that of hydrogen peroxide solution.Gas phase oxidation is based on ozone as oxidant.A new batch oxidation device and fluidized bed oxidation device were designed and manufactured.The oxidation process of batch mixer and continuous fluidized bed oxidation was studied.The experimental results show that in the batch oxidation process,with the increase of oxidation time,the value of pH decreased,the volatility increased,the fluidity increased,the tinting strength and blackness basically unchanged.Combined with infrared spectrum and XRD spectrum,we can draw a conclusion:the oxidation reaction can increase the number of oxygen-containing functional groups on the surface of carbon black,but has no effect on the structure and particle size of carbon black.The optimum process conditions of batch oxidation are ozone concentration of 80g/rrrm3 and oxidation time of 1 hours;In the fluidized bed oxidation process,the change of reaction temperature has no effect on the oxidation effect.While the effect of changes in the ozone flow rate,ozone concentration,static bed height,reaction time and other process conditions on the oxidation efficiency is very obvious.However,with the change of process parameters,the oxidation degree of carbon black will reach saturation.The optimum process parameters for the pilot plant of the fluidized bed oxidation process is as below:reaction at room temperature,60-90min reaction time,100mm static bed height of carbon black,0.03m/s ozone flow rate and 10g/m3 ozone concentration.Oxidation and direct dispersion method are combined.The oxidized carbon black was used as raw material,and mixed with dispersant,wetting agent,defoaming agent,bactericide and deionized water,to produce water paste in the vertical sand mill grinding.The effects of carbon black content,dispersant dosage and grinding time on the tinting ability of colour paste were studied.The best preparation process for water color paste is:dispersant agent HY2200 dosage of 25%,wetting agent HY1600 dosage of 2%,oxidized carbon black BH-1 content of 40%,in the sand mill grinding for 4 hours.