Synthesis Of PAMAM Dendrimer And Its Application In The Papermaking Wet End

Chemically assisted retention and drainage program played a crucial role on papermaking process and paper quality. The demand for retention and dewatering aids has grown because of the following trends in pulp and paper industry: the transform of acid paper to neutral or alkaline paper, the higher extent of closure of white water, the increase of paper machine speed and the application of more recycled fibers.Polyamidiamine (PAMAM) dendrimers were synthesized by divergent growth. The initial core, ethylenediamine was first reacted with methyl acrylate by the exhaustive Michael addition in methanol to give ester-terminated PAMAM dendrimers of half-generation, then the purified products were reacted with a large excess of ethylenediamine by exhaustive amidation to give amine-terminated full-generation PAMAM dendrimers. By reiterating the synthetic process of Michael addition and the amidation, the G0.5 to G 10.0 PAMAM dendrimers were synthesized.The composition and structures of PAMAM dendrimers were characterized by means of FT-IR, 1H-NMR and 13C-NMR, elemental analysis and acid-base titration of amine groups. The charge densities of Gn.0 PAMAM dendrimers were measured by colloidal titration. The results showed that the PAMAM dendrimers synthesized were dendritic structure and well defined, with higher charge density.The exterminal groups of full-generation PAMAM dendrimers were modified using 3-chlorine-2-hydroxy propyltrimethyl ammonium chloride (CTA), and the structure of CPAMAM dendrimers were characterized by means of FT-IR acid-base titration of left amine groups. The charge densities of CPAMAM dendrimers were measured by colloidal titration. The results showed that the CPAMAM dendrimers were modified with higher charge density than PAMAM dendrimers. Modification of the ester-terminated PAMAM dendrimers is an effective approach to prepare spherical monodispersed microparticle, bearing anionic charges on surface. The exterminal groups of half-generation PAMAM dendrimers were modified in NaOH solution, and the structure of APAMAM dendrimers were characterized by means of FT-IR. The charge densities of APAMAM dendrimers were measured by colloidal titration. The results showed that the APAMAM dendrimers were modified, with anonic charge density.The retention and drainage performances of single PAMAM dendrimers, single CPAMAM dendrimers, dual-polymer and microparticle retention and drainage system were investigated in the bleached ONP deinked pulp. The factors such as the dosage, pH value, shearing and time were discussed. The results showed that higher generation CPAMAM dendrimers have better retention and drainage effect than PAMAM. It has also been found that the effective flocculants of ingredients could not be obtained by CPAMAM alone. However, the combination of CPAMAM dendrimers with anionic polyacrylamide (APAM), especially with cationic polyacrylamide (CPAM) did significantly improve the retention efficiency, the latter. When used together with CPAM and organic cationic microparticle (bentonite or colloida silica), the microparticle system showed excellent retention and drainage performances, even in high pH value and high shearing.The high generation APAMAM dendrimers were used as anonic organic particulate for the microparticle retention and drainage system. The results showed that high generation APAMAM dendrimers accompanied with CPAMAM dendrimers and CPAM could provide higher furnish retention. It has also been observed that the APAMAM dendrimers had a strong synergetic effect with bentonite or colloida silica in the microparticle retention and drainage system.