Research On High-quality Of Recycled Carbon Black From Waste Tires

With the gradual development of the automobile industry,the scale of wasted tires in China has become larger and larger,which not only cause waste of resources,but also produces serious black pollution.How to recycle waste tires in a green and efficient way has become an urgent problem to be solved on the road of building a resource-saving society in China.Pyrolysis of waste tires is an environmentally friendly treatment method,which not only solves the problem of disposal of waste tires,but also produces valuable products in three forms:solid,liquid and gas.35-45 wt.%of the product is called waste tire recycled carbon black（rCB）.Compared with commercial carbon black,rCB has weak reinforcing properties in rubber and has not been widely used so far,which is an important reason restricting the development of waste tire pyrolysis industry.Therefore,this paper studies the reasons for the inactivation of rCB,and proposes some targeted modification.Finally,based on the principle of environmental protection and economy,two comprehensive application schemes are proposed,which provide some theoretical guidance for the wide application of rCB.In this thesis,the properties of rCB itself were firstly characterized,and the reinforcing performance of rCB in NR was investigated and compared with commercial carbon blacks N330 and N660.The reasons for the poor reinforcement performance of rCB in rubber were discussed.The results showed that the particle size of rCB was larger and the distribution range was wider;the surface of rCB was covered with a layer of organic impurities,which covered the active sites and reduced the specific surface area;the ash content of rCB is as high as 15.97%,which is mainly composed of metal compounds dominated by Zn O and non-metallic compounds dominated by Si O₂;the reinforcing properties of rCB in NR are far from that of commercial carbon blacks N330 and N660,but the chemical structure is not damaged,and it still has the potential to restore the reinforcing properties.Secondly,aiming at the problems of too large particle size,organic impurities and high ash content of rCB,the methods of ball mill grinding,high temperature treatment in N₂atmosphere and pickling were adopted to improve its reinforcement performance in rubber.The experimental results showed that grinding rCB with a ball mill can reduce the particle size to a certain extent,but cannot fundamentally eliminate the influence of the mutual adhesion of carbon black aggregates.This modification method has no significant effect on improving the reinforcing performance of rCB;high temperature treatment in N₂ atmosphere could effectively removed organic impurities covering the surface of rCB,increased the specific surface area and exposed more active sites.High temperature treatment improved its reinforcement performance.Under the experimental conditions of this paper,the best treatment method is 500℃constant temperature for 30 mins;organic impurities covering the surface of rCB will hinder the contact between ash and acid solution,so pickling after removing surface impurities at high temperature could improve the efficiency of pickling,reduced the ash content to about 6.5%,improved the content of carbon element,and the modification with titanate coupling agent after pickling could avoid the agglomeration caused by excessive surface activity of carbon black and improve the dispersibility.Finally,based on the above research,in line with the principles of cost saving,we explored two comprehensive application schemes.（1）On the basis of high temperature modification,this paper introduces the concept of true parts.Due to the high ash content of rCB,the carbon element content is only about 82.6 wt.%of the total mass.We increased the amount of rCB to achieve the rubber formula required amount of effective carbon.Finally,it was mixed with commercial carbon black N330 according to a certain proportion,and it is found that a higher reinforcement level could still be achieved.（2）Similarly,on the basis of high-temperature modification,since Zn O in ash can still play the role of vulcanization activation after pyrolysis,we appropriately reduced the amount of Zn O in the mixing process and found that the mechanical properties of the composites were improved.Some theoretical suggestions are provided for the application of rCB in rubber in the future.