The Research Of Alkyl Ketene Dimer Sizing Problem On Causticized Calcium Carbonate Filled Paper

Causticized clacium carbonate(CCC)is a by-product produced in kraft pulping mill.It can be used as paper filler,this is an effective way to make full use of the waste sludge.Nevertheless,it still has its problems in practical application,especially the AKD sizing problem.This paper firstly analyzed the filling properties of CCC and made a comparison with commercial calcium carbonate,then focused on the reason for CCC's influence on AKD sizing,in order to provide essential theory basis for the improvement of filling application and the optimization of causticizing process.First,compared with the original CCC,the final CCC had obvious poorer AKD sizing efficiency.This maybe caused by the presence of silica gel generated in the carbonization process,which caused the final CCC a higher specfic surface area and pore volume.Based on the research made above,the pH value of carbonization end should be controlled to prevent the generation of silica gel.The results of research indicated that the silica gel was guadually forming when the pH value was less than 8.5.The hydrated calcium silicate was transformed into silica gel completely when the pH dropped below 8.At the same time,the AKD sizing efficiency of CCC declined sharply.Therefore,controlling the carbonization end at 8.5 could be apt to get a good removal of residual alkali and ensure a good AKD sizing efficiency.Then,using the grinding and centrifugal way to remove the silicon material in the CCC.The results showed that the factors that influence removal efficiency of silicon from big to small was: grinding particle size,the centrifugal rotational speed and centrifugal time.Among them,grinding particle size of silicon class influence on material removal rate,and it also confirms part of the silicon material is wrapped in calcium carbonate particles,were released after grinding,and then can be removed by means of centrifugal.And the CCC was pre-flocculated with cationic polyacrylamide(CPAM)and cationic polyamine.The results showed that CPAM had a better effect on the improvement of CCC's sizing efficiency.In addition,the modification of styrene butadiene latex(SBL)to the final CCCsamples was studied.The experimental results showed that the AKD sizing efficiency was improved significantly after the modification,and the sizing efficiency increased by about 50% compared with the unmodified CCC.But with the increasing amount of latex,the improvement is not big.What's more,the retention rate of the modified CCC was improved obviously,and the modified CCC increased by about 10%.Finally,through the research of above,the apt methods could be concluded to improve the CCC's sizing efficiency.We use the CCC of Fangyuan mill to have a process to make as a filler in the laboratory.And controlling the pH end of carbonization process.Then use CPAM to pre-flocculate under an optical condition,and found that the sizing performance of AKD has improved significantly.Even in the case of high loading,optimized the CCC sizing performance is better than the original lime mud in the same condition,the optimization of CCC and fill out the paper tensile strength increased,brightness changed little,opacity down slightly.