The Research Of Quality Decay And Hornification Of Secondary Fiber During Recycling

The secondary fiber recycling has great significance. However, the fiber properties decaywill occur in the recycling process, and the adverse impact of the waste paper recycling isgrowing. So the need to the thorough research of the fiber quality decay reason is also urgent.In order to examine the secondary fiber recycling hornification case, the paper firstltystudied the relationship between fiber morphology, paper physical strength and fiberhornification. And the study simulated the factory secondary fiber recycling process with fivetimes using the domestic waste newspaper pulp (ONP) as raw materials, and the fiberrecycling situation compared with the softwood pulp and reed pulp. Then the research focusedon examining the chemical composition and microstructure of ONP fibers, and explored thehornification mechanism for ONP fiber. The effect of hemicellulose on fiber horinificationwas known in the experiment, then the essay emphatically discussed the influence ofhemicellulose content on secondary fiber horinification. The effect of different hemicellulosecontent(23.91%,19.54%and8.08%) on fiber horinification and paper physical strength wasexamined with reed pulp fiber as raw material.(1)The secondary fiber horinification caused fiber morphological changes. The fiber weight,coarseness, kink and curl index of ONP were reduced, while the fiber length was changedlittle. Compared with ONP, the fiber length of softwood pulp and fiber coarseness of reedpulp were decreased obviously, while fiber kink and curl index of softwood and reed pulpalso were increased.(2)The secondary fiber horinification caused paper physical strength decreased. The papertensile and burst index of ONP were significantly decreased, while the tear index wasincreased slightly, but changed little. Compared with ONP, the paper tensile index ofsoftwood and reed pulp were increased firstly and then decreased, while the tear indexreduced significantly. The fiber horinificaiton made the fiber water retention value reduced,and was closely related to the fall in the paper tensile index.(3)The secondary fiber horinification lead to the fiber chemical composition changed. Thefiber hemicellulose content and lignin content were both reduced. Fiber horfinication made the fiber surface carboxyl content decrease, which lead to the fiber surface hydrophilicitydecline.(4)The secondary fiber hornification made fiber surface pore was irreversible closed. Thefiber infrared crystallization index, cellulose crystallinity and crystallite cross-sectional areawere increased during recycling, which indicated that cellulose cocrystallization phenomenonwas the internal cause of fiber hornification, and lead to the fibers swelling reduction, thenfurtherly changed into paper strength.(5)The hemicellulose content influenced the fiber hornification. The resultes show that highcontent of hemicellulose(content was23.91%) can break the effects in squeezing and dryprocess on fiber hornification. For lower hemicellulose content (content of8.08%) fiber, thesqueezing and dry process had more serious influence on fiber hornification than the effect ofhemicellulose content change. Reducing the hemicellulose content, the secondary fiber tensilestrength and burst index fell sharply. And retaining high levels of hemicellulose in thesecondary fiber could make the tensile index and burst index maintain at a high level, andcould remit the quality decay of secondary fiber. However, the tear index did not changesignificantly with the decreasing of hemicellulose content.