Preparation Of Microfibrillated Cellulose And Its Application In Modification Of Ground Calcium Carbo Nate For Filling

Natural cellulose is the most abundant biomass resource on earth,and is the most popular biological macromolecular,which widely exists in the wood,cotton,hemp,grass,some bacteria and other organisms.Microfibrillated cellulose(MFC)is a kind of new natural nanoscale polymer material and can be prepared by mechanical processing.Due to its large length to diameter ratio and specific surface area,high transparency and strength,coupled with widely available,biodegradable,renewable and other excellent properties,it has potential applications in the fields of medicine,textile,paper making,food and so on.Firstly,bleached hardwood sulfate pulp,used as raw material,was oxidized by2,2,6,6-tetramethyl piperidine-1-nitrogen oxide(TEMPO)and then ground to prepare TEMPO oxidized cellulose nanofibrils(TOCN).Based on the single factor experiment,the optimum condition of TEMPO oxidation pretreatment was determined according to the influence of chemical dosage on the degree of polymerization and carboxyl content of the oxidized fiber.The dosage of NaBr,TEMPO and NaClO were 1.5 mmol/g,0.05mmol/g and 7 mmol/g,respectively.The obtained TOCN was then added to the bulk GCC to form MFC-modified GCC fillers.According to the tensile index of the papers filled with modified fillers,the optimum dosage of three kinds of cationic additives were determined as follows: FL2949(0.05%),CS(0.05%),and FL4540(0.025%).The results of the tensile strength of paper and light scattering coefficient showed that cationic starch is more suitable for MFC modified GCC than polyamine cationic additives.Secondly,MFC was prepared by TEMPO oxidation pretreatment and mechanical grinding in the presence of a certain amount of GCC.The effect of GCC dosage and grinding concentration on the fibrillation was investigated.The properties of MFC-modified GCC fillers were studied and compared with that of the traditional GCC fillers.Results showed that the resulting fibrils became more uniform when the dosage of GCC was 10%~15% and the concentration of the suspension was 6.97%.The propertiesof papers filled with co-grinding MFC-modified GCC fillers were better than that of the non-modified fillers.Finally,the performance of GCC fillers modified by MFCs that prepared by different pretreatment methods and from different pulps was compared.Results showed that the average particle size of the MFC-modified GCC fillers was increased compared to traditional GCC,and GCC particles distributed along the length direction of the MFC.Compared to the pulp filled with traditional GCC,the drainage ratio of pulps filled with GCC which modified by enzyme and PFI pretreated MFC was not decreased under the same tensile index of papers,meanwhile,the filler retention ratio was improved.When the ash content was consistent,the tensile index of paper filled with MFC-modified GCC(except for corncob MFC-modified GCC)improved significantly.However,the sizability of the papers filled with MFC-GCC filler paper was decrease.In addition,the light scattering coefficient of the papers filled with TEMPO pretreated MFC-GCC fillers was reduced,but it was increased by about 18% when GCC fillers modified by MFC prepared from chemical mechanical pulp were used.