The Technology Of Filler Encapsulation Combined With Pre-flocculation And Its Effect On Paper Properties

The main purpose of adding fillers to the paper matrix is to lower furnish costs.Conventional unmodified fillers are usually very small in particle size,and the filler can not produce hydrogen bonds which play an important role in retaining the fillers within the paper wet web.In order to effectively increase the retention of the filler and to improve filler-fiber bonding in paper,this study proposed a technology of pre-flocculation combined with encapsulation.CaCO3 fillers are modified with APAM/CSt/CPAM treatments and their morphological characteristics are studied.The results show that APAM contributes to the uniform dispersion of CaCO3;then,CSt and APAM form a stable polyelectrolyte complex(PEC)which is spontaneously deposited on the surface of CaCO3,forming encapsulated fillers;finally,CPAM can flocculate the encapsulated fillers,forming larger particles which are more easily retained onto the wet web of paper.The treated fillers were used to forming handsheet of paper.It was found that,compared to the unmodified fillers,the treated ones contributed to higher drainage rate and retention ratio of the fibers and fillers.As a matter of fact,the increase of retention was very obvious,as the retention of the encapsulated and preflocculated fillers was about 3 times that of the unmodified filler.More interestingly,the paper achieved much higher ash content as 2.18 times improved,however,the paper strengths were impaired not much.The treated fillers were also used for papermaking with additional use of a retention and drainage aid system.Higher ash contents were found in this case than that investigated in the above without the use of retention and drainage aids.Scanning electron microscope was used to observe the fillers in the paper sheets,with the result that the modified fillers were in large size and they attach well to the fiber.A technology called focused beam reflectance measurement(FBRM)was used to investigate the changes of particle size and average chord length during the modification with different kinds of APAM,CSt and CPAM which under different shear forces.And the larger the rotational speed was,the smaller the larger particles were formed when the rotational speed set from 250 r / min to 750 r / min.At the same time,the modified fillers had a good resistance to shear stability.It is concluded that the technology of filler preflocculation combined with encapsulation has great potential to be used in real papermaking processes.