RAFT Grafting Polymerization Modification Of Cellulose And Its Application In The Papermaking

The amount of fillers in paper and the requirement to the paper strength of people are increasing year by year, which conduce that the exploitation of paper potentiator is one of the most important work all the time. However, the reserves of non-renewable resources such as coal, oil, and natural gas have already can not satisfy the requirement of economic development. Therefore, the exploitation, research and application of natural organic polymers as cellulose, hemicellulose, lignin, and protein have caused wide attention of researchers both domestic and abroad. Cellulose has many advantages such as abundant, cheap, biodegradable, renewable, and easy modified and so on. Preparing graft copolymerization functional products with cellulose as skeleton opens a new way to the high-valued application of cellulose.In this paper, 1-butyl-3-methyl imidazole chloride salt ([Bmim]Cl) ionic liquid and N, N-dimethylformamide (DMF) were used as the reaction medium, monemers [2-(methacryloyloxy)ethyl] trimethyl ammonium chloride (DMC) and acrylamide (AM) were grafted onto the cotton cellulose by reversible addition-fragmentation chain transfer (RAFT) technique homogeneously, then the grafted products were used as paper potentiator.Firstly, cellulose-based macroinitiator (Cell-CPAC) was synthesized by the homogeneous reaction of cotton dissolved pulp and acylation reagent 2-chloro-2-phenyl acetyl chloride (CPAC) in [Bmim]Cl/DMF, and FT-IR,1H NMR and 13C NMR confirmed the successful synthesis of Cell-CPAC. The effects of molar ratio of CPAC/anhydroglucose unit (AGU), reaction time, reaction temperature, kind of acid-binding agent, and cellulose concentration on the degree of substitution (DS) of Cell-CPAC were studied. The reactivities of the three hydroxyl groups in AGU with CPAC were also investigated. The results showed that when reaction time was 24 h, reaction temperature was 35℃, the molar ratio of CPAC/AGU was 6:1, cellulose concentration was 3%, pyridine was acid-binding agent, Cell-CPAC obtained the maximal DS 1.114. Furthermore, the three hydroxyl groups satisfied the order of C6>C3>C2, and the acylation of cellulose with CPAC decreased the thermal stability of cellulose.In DMF, Cell-CPAC reacted with dithiobenzoic acid (DTBA) to synthesize cellulose-based macromolecular chain transfer agent (Cell-CTA), and the successful synthesization of Cell-CTA was confirmed by FT-IR and element analysis. The effects of molar ratio of DTBA/Cell-CPAC, reaction time, reaction temperature, kind of acid-binding agent, and the concentration of Cell-CPAC on the DS of Cell-CTA were researched. The results showed that the optimal reaction conditons were:reaction time of 24 h, reaction temperature of 40℃, molar ratio of 3:1 (DTBA/Cell-CPAC), Cell-CPAC concentration of 1%, using pyridine as acid-binding agent. Furthermore, the reaction of Cell-CPAC and DTBA decreased the thermal stability of Cell-CPAC.In the homogeneous system [Bmim]Cl/DMF, monomers DMC and AM were grafted onto Cell-CTA with the initiator of azodiisobutyronitrile (AIBN) to synthesize the cellulosed-based cationic graft copolymer (Cell-g-DMC-AM), and FT-IR and 1H NMR testified the successful graft of DMC and AM onto Cell-CTA. The effects of reaction temperature, reaction time, and the molar ratio of Cell-CTA/AIBN on the monomer conversion, intrinsic viscosity, cationic charge density and Zeta potential of every Cell-g-DMC-AM samples were discussed. The results showed that the best reaction conditions were:reaction temperature of 60℃, reaction time of 36 h, molar ratio of 1:0.4 (Cell-CTA/AIBN). Furthermore, Cell-g-DMC-AM had a two-step degradation profile, which was another evidence of the successful synthesization of Cell-g-DMC-AM.Cell-g-DMC-AM was used in alkaline hydrogen peroxide mechanical pulp (APMP), and studied the potentiation for APMP. The effects of reaction temperature, reaction time, the amount of sample, pH and shear force on the potentiation were researched, and the sheets were analyzed by XRD and SEM. The results showed that Cell-g-DMC-AM could improve the tensile index, tear index and the bonding strength between the fibers significantly, but had little effect on the strength of the fiber. The optimal conditions of Cell-g-DMC-AM were:reaction temperature of 40℃, reaction time of 10 min, dosage of 0.5%, pH of 7, shear foce of 200 rpm. The SEM of the sheets indicated that the conjunction points of fibers increased, and the uniformity was improved. In addition, the use of Cell-g-DMC-AM could not affect the secondary recycling of sheets.