Studies On Dissolved And Colloidal Substances In Chemical Mechanical Pulp

The high-yield chemical-mechanical pulp has become more and more important for papermaking in recent years. Some dissolved and colloidal substances which called DCS such as resin acids, fatty acids, polysaccharide, pectic acids and ligin-like substances are released into the pulp suspension from chemical-mechanical pulp. These substances badly affect the quality of paper and the wet chemisty.Poplar APMP and BCTMP were used as raw materials. DCS which were produced in the production process have been researched systematically. Firstly, the characterization of DCS was studied, and the DCS was determined by GC-MS both qualitatively and quantitatively. Secondly the effects of DCS on the physical, optical and drainage properties of pulp were studied. Finally the effects of cationic polymer and pectinase treatment on DCS were performed.The results showed that the DS contributed about 60% to the total DCS and the ash content was about 50%. Colloidal substances mainly contributed to the turbidity and the cationic demand. The conductivity of the DS was quite similar to that of the DCS, indicating that DS had a key effect on the DCS conductivity. MTBE extracts of DCS water samples were characterized and nine compounds of the fatty acids which were determined quantitatively were: dodecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, oleic acid, linolenic acid and stearic acid. Six compounds of the carbohydrate components which were quantitatively determined were: xylose, arabinose, glucose, galactose, galacturonic acid and mannose.DCS has an extremely disadvantageous influence on the paper brightness and the physical intensity performance. Increasing the content of DCS would result in the decrease of brightness. The DCS influenced the hydrogen bond among fibers and decreased the bond of fibers, furthermore resulted in the decrease of the tensile and burst strength. Colloidal particles could fill up spaces of paper and then decreased the tear strength. On the other hand, the increased content of DCS in the system could decrease the function effect of CPAM, which can be explained by the theory that the cationic polymers tended to be preferably adsorbed on the DCS and formed electrolyte complex, which reduced the flocculation of the CPAM.Pectinase treatment can decrease the cationic demand in a certain extent. The cationic demand of APMP and BCTMP water samples decreased by 24.2% and 20.3% respectively when the treatment time was one hour and the dosage of pectinase was 30 APSU/L. The addition of cationic polymer additives could destabilize DCS. CPAM and cationic starch destabilized DCS by bridging mechanism, but PDADMAC destabilized DCS by charge neutral mechanism. Combining cationic polymer additives with pectinase treatment can decrease the cationic demand of water samples more effectively.