Study On The Application Mechanism Of Chitosan Microparticle Retention And Drainage System

The papermaking wet-end system is becoming more and more complicated,high-speed and closed,which puts forward higher and higher requirements for the retention and drainage system of the wet end.However,the traditional additives are mostly fossil-based products,which are difficult to meet the requirements of biodegradation and sustainable development.Therefore,it is urgent to explore environmentally friendly bio-based retention and drainage products suitable for modern wet end systems.Chitosan is a natural cationic polymer with biodegradability,regenerability,biocompatibility and bacteriostasis.It can be combined with Bentonite/nanosilica to form ideal particle retention and drainage system.In this paper,the chitosan-bentonite(Cs-Bent)and chitosan-nanosilica(Cs-Ns)microparticle retention and drainage system were the main research objects,and the Cs single system、 Cs-Bent particles system 、 cationic polyacrylamide-bentonite(CPAM-Bent)microparticle system、Cs-CPAM-Bent ternary particle system and Cs-Ns nanosystems were analyzed and compared.The effect of D.D.and MW on Cs-Bent system were explored;The effect of Cs dosage(factor A),Ns dosage(factor B),shear rate(factor C)and shear time(Factor D)on the Cs-Ns system were explored through single factor analysis;The addition process of the Cs-Ns system was optimized based on the full-factor experiment of Mintab software.Research indicates:(1)Compared with the Cs system,the Cs-Bent system could form more uniform and dense micro-flocs,and improved the retention,drainage,paper formation,and strength index by 41.35%,32.28%,9.28%,and 9.05% respectively.Its uniformity and strength is better than the blank without added retention agent,so the chitosan particle retention system could solve the problem of formation and strength loss caused by Cs single system.(2)Comparing the bentonite particle retention system,it was found that the Cs-Bent system is superior to the CPAM-Bent system in terms of retention and drainage performance,but has advantages in improving the formation and tensile strength of the paper.The formation and tensile strength were increased by 178.41% and 71.13%,respectively,compared with the CPAM-Bent system.The Cs-CPAM-Bent system combined the advantages of both to achieve high retention,high drainage,high paper formation and high strength and solved the contradiction between the high retention rate and the low formation/strength of the CPAM-Bent system.(3)In CS-Bn system,chitosan with low MV /middle D.D.had the greatest retention/drainage rate,and the higher the D.D./MV was,the better the paper formation and strength would be.The chitosan with low MW synergizes well with bentonite,and the chitosan with high MW have poor re-flocculation with bentonite.(4)Compared with the blank sample,the Cs-Ns nanosystem improved the retention rate,drainage performance,and paper tensile strength by 119.03%,17.78%,and 5.24%,respectively.This indicates that the Cs-Ns nanosystem combines the effects of retention and drainage and paper reinforcement.Compared with the Cs system,the Cs-Ns nanosystems increased the retention,drainage,tensile and formation index by 9.90%,11.20%,6.50%,and 0.85%,respectively.It showd that the addition of a small amount of Ns can significantly improve the retention and drainage performance of the Cs unit system and improve the tensile and formation properties.(5)Through the single-factor experiment of Cs-Ns system,it was found that with the increase of Cs dosage,the retention and uniformity index decreases,and the tensile index increases.With the increase of Ns dosage,the drainage performance,tensile index and uniformity index all showed a downward trend,and the retention rate decreased first and then increased.The retention was not significantly affected by the shear time,and the drainage,uniformity and strength index were all optimal at 45 s.The retention was good at low shear rates,and the paper tensile index was good at high shear rates.The formation index and drainage were best at a shear rate of 1000 rpm.The system did not rely on high shear to destroy the flocs and it had strong re-flocculation and shear resistance under high shear.(6)In order to optimize the process,a full-factor experiment was carried out by Mnitab software.The optimal solution for the retention and drainage performance,the uniformity index and the tensile index were A0.05%-B0.15%-C1000rpm-D45 s,A0.5%-B0.05%-C1400rpm-D45 s,A1.5%-B0.05%-C1400 rpm-D45 s respectively.