Modification Of Tara Gum And Its Application For Improving Performance Of CTMP

In recent decades, concerning on the shortage of energy and resources as well asthe impact to the environment, more and more efforts have being paid to how toefficiently utilize renewable resources for producing bio-chemicals and bio-materials byboth of scientific and industrial communities. As an environmental-friendly chemical,polysaccharide gum prepared from plant resources is being used as functional aids inthe paper-making process, to get improved pulp drainage and fines retention, andenhancement of paper strength properties. Usually, natural non-ionic Tara gum (TG) isnot easy being retained by pulp fibers, that limited the application in the papermakingprocess, therefore, some approaches such as modification processes are employed toimprove the performance of TG products.In this thesis, the composition, structure, and rheological properties of TG wereinvestigated, and three approaches were adopted for modifying TG, which include thequaternary ammonium cationic modification, the carboxymethyl modification and thecrosslinking modification. The influence factors in modifying TG were discussed.Furthermore, the modified TG products were applied to the chemithermal mechanicalpulp (CTMP), and their effectivenesses in improving pulp properties were investigated.It was showed that the TG demonstrated typical characteristics of plantpolysaccharides, and it was mainly consisted of galactose and mannose (mass ratio ofgalactose/mannose was4.2:1), meanwhile, involved with a small amount of arabinose,glucose and xylose. The viscosity of TG solution was increased with the increase ofconcentration. The solution also showed both characteristics of viscosity and elasticity,and it was sensitive to the shear stress. Basically, the solution gave a higher viscocity asthe shear rate was lower than80Hz, but a higher elasticity as the shear rate higher than80Hz.It was suggested to prepare the quaternary ammonium cationic Tara gum (CTG)under the condition of m(CHPTAC): m(TG)=0.3:1; m(NaOH): m(TG)=0.3:1;temperature of60°C; and reaction time of3hours. The parameters affected thesubstitution degree of TG were examined by way of orthogonal experiment, and theinfluence was followed as a sequence of: NaOH/TG mass ratio> reaction temperature>CHPTAC/TG mass ratio> reaction time. The surface charge density was increased withincreasing the DS value. FT-IR and1H NMR analyses confirmed that the cationic groups were introduced to the molecules of TG. Applied the modified TG to the CTMP,it showed that the tensile and burst strengths of handsheets were significantly improved,better result was achieved when adding the modified product under neutral or alkalineconditions. Compared with the untreated TG, addition of CTG reinforced the strengthproperties of CTMP, moreover, the CTG acted also as retention aids to retain fines andfillers. Better retention was achieved as adding0.4%of CTG under neutral or alkalineconditions. A higher substitution degree of CTG showed a higher retention ratio. Itshould be noticed that the CTG was not exhibited shear resistant ability. Severalretention systems were examined and compared, and applying CTG with CPAM gave asynergistic effect.The anionic Tara gum (ATG) was prepared by reacting the tara gum (TG) withsodium chloroacetate, and an appropriate condition was acquired as follows: m(NaOH):m(TG)=0.3:1, alkalizing treatment for30min, m(sodium chloroacetate): m(TG)=0.4:1, andthe reaction was conducted at70°C for2hours. Further investigation with FT-IRverified that the carboxymethyl group was introduced to TG molecules. Throughmodification, the acquired ATG showed a better light transmittance than the original TG.By adding ATG into the CTMP, strength properties of handsheets were distinctlyimproved, and a better reinforcement was achieved with the ATG dosage of0.3%andcarboxyl group content of2.83%respectively.Through crosslinking the TG with borax can further improve the performances,and the acquired Tara-B showed a higher resistance to shear force. Similarly, the Tara-Bshowed the same strength improvement when applied to the CTMP, and a betterachievement acquired with a dosage of0.3%. The pH value of Tara-B was affected to alarge extent by the surface anionic charge demand. Compared with the Tara/CPAMsystem, combining Tara-B and CPAM demonstrated a better reinforcement to the pulpproperties. Tara-B was contributed to the retention of fines and fillers, furthermore, theassociation of Tara-B/CPAM showed a better retention than the Tara/CPAM.