Synthesis Of Amphoteric Polyarylamide And The Mechanism For Strengthening Recycled Fibers

Recycled fibers have become the dominant raw material in papermaking industry due to the adjusting strategy of papermaking materials. However the recycled fibers are of serious problem in papermaking process. And the strengthening effect for recycled fibers of thetraditional paper strengthening agents is insignificant, which lead to research in a new additives which is aiming to strengthen the recycled fibers. This paper focused on experiment related to amphoteric polyacrylamide (AmPAM) and aqueous solution polymerization was used to synthesize AmPAM and the polymer were used in fixing secondary fiber to explore the strengthing effect and mechanism.The experimental result are as follows:(1)The percent conversion, viscosity and molecular weight of synthesized polymers are variational according to the synthesized condition and the monomer ratio effect coversion rate the least. The viscosity of synthesized polmers are changing as the variate of experiment variaed and the viscosity and molecular weight of synthetic product reached to the minimum. Synthetic polymer was analyzed through IR and TG which proved the structure and heat stability.(2)AM, IA, MBA and DMC was used to synthesize amphoteric polyacrylamide (AmPAM) and different products were gained by changing the synthetic timing,temperature, pH value monomer ratio and initiator dosage and these polymers were added into secondary fibers to do the strengthening test of paper which indicated that the polymers had significant strengthening effect for paper made of recycled fibers. The other physical properties of polymers combined with the physical strength of paper indicated the best synthetic condition of the AmPAM was when the synthetic timing, temperature, pH value monomer ratio and initiator dosage were at 6h,70 ℃,7,2:0.3:0.3, and 0.6% respectively.(3)AmPAM was synthesized as the optimal reacting condition and added into the recycled fibers to confirm the best adding process. When the adding dosage of AmPAM was 2%, the tensile index, bursting index and tearing index of paper increased by 70.7% ,9.9% and 9.6% respectively compared to the nonadding paper. And as the adding dosage of AmPAM increased the paper strength ascended accordingly when the adding dosage was 2% the inceased along with the pH value increased when the pH value was than four after which the paper strength began to fall. Comparing with the non-adding paper, the paper strength reached the peak value when pH value was four and the tensile index, bursting index and tearing index of paper increased by 74.8% ,25.1% and 24.6% respectively. When pH value was seven, the tensile index, bursting index and tearing index of paper increased by 70.3% ,9.6%and 13.4% respectively.PAC was used with AmPAM to strengthen paper in this paper and when the adding dosage of AmPAM was 2% along with the increasement of adding PAC into pulp, the paper strength presented a trend of rising when the dosage was less than 0.2%. When the adding dosage of PAC and AmPAM was 0.2% and 2% the tensile index, bursting index and tearing index of paper increased by 75.1% ,25.2% and 18.4% respectively.(4)The strengthening mechanism of AmPAM was verified through retention, drainage, Zeta potential SEM and XPS test and the result showed that AmPAM could increase the retention of fines in pulp leading to increasement in drainaging rate. When the fines were retained in the paper, the structure of paper would be compacted which led to better performance in paper strength. And the Zeta potential experiment showed that when the Zeta potential reached to a relative small value, the paper strength woule be better. This explained the variation tendency of strength as the adding dosage and pH value changed. The water retention value of fibers indicated that AmPAM could significantly improve the WRV of recycled fibers, the WRV of recycled fibers increased by 31.4% after adding AmPAM.Comparing to the non-added paper, the structure of paper added with AmPAM was more compact in the SEM scanning chart and the void between individual fibers was filled by polymers which illustrated that polymers added into pulp formed a net structure during the strengthening process which contributed a lot to the paper strength. AFM tests showed that acrylamides copolymer were filled in the blanks between fibers. XPS experiment illustrated that comparing to commercial AmPAM and CPAM, the relative adsorption of synthesized AmPAM on paper was more.