Investigation On The Distribution And Study On The Characteristics Of Stickies In The Dip Production Lines

Recycles fibers are nowadays an important raw material in the pulp and paer industry. Recent decades, deinked pulps are increasingly used to produce high paper graders such as newsprints and supercalendared papers. However, components of deinked pulps are more complicated than the pulps of virgin fibers, which include not only fiber and fines and fillers but also lots sticky contaminants. Sticky contaminants remain a major problem in producing papers with deinked pulp, which originated from ink binding adhesive, coating adhesive, hot melt adhesive, pressure-sensitive adhesive from waste papers, as well as lipophilic wood components released during the repulping process. Therefore, to reduce the obstacles caused by the stickies, it was necessary to investigate stickies remained in the pulp suspension, so that appropriate approaches can be selected to control them. In this paper, investigation was carried out on a commercial deinking pulping plus nowsprint production line. Pulp samples were taken from the major points of the deinking process and papermaking system, and the samples were classified in fibers, fines and water fractions. Followed, the chemical components existed in about three fractions were analyzed by FTIR and GC-MS, and their changes based on the sampled points along the production line were discussed. Forethermore, effect of storage temperature on deinking process and characteristics of sticky contaminants were examined.Fiber and fines fractions from pulps sampled from the major points of the production line were extracted with tetrahydrofuran (THF). The reults showed that the THF-extractives reduced by about 74% (in fiber fraction) and 35% (in fines fraction), respectively, for pulps from the dumping tower to the head box. FTIR analysis showed that, the saturated fatty acid ester, poly vinyl acetate, poly acrylate, organic compounds with Si-O bond and o-substituted of benzene were detected in the extractives in fiber and fines fractions, for the pulps sampled from the heat disperser, the post-flotaion and the paper machine chest. For further discussion, sticky contaminants analyzed by GC-MS can be categorized as adhesives, wood extractives and lignin-derivatives. Adhesives remained as major components in extractives for fibers and fines, respectively. Compared with the pulp after heat dispersing, sticky contaminants slightly increased for the fiber fraction, but decreased to some extent for the fines fraction. It is easy to understand that the flotation removed particles whose sizes in the range of flotation. With addition of cationic polymers, componds in fibers and in fines fractions were to some extent increased from the post-flotation to the machine chest. Compared with the pulp sampled from the machine chest, less sticky substances were examined in the final papers, which indicated that lots sticky substances remained in the water system or tend to deposit onto the machine parts.Sticky contaminants in water phases separated from pulps sampled from the major points of the deinked line were investigated. The results showed that DCS decreased by about 57%, from the dumpling tower to the head box. Water samples were extracted with MTBE, and the MTBE-extractives were analyzed by GC-MS. Sticky substances can be catagrized as addihesives, wood extractives and lignin-derivatives and other organic acids. Among them, addihesives remained major components. Some contaminants in forms of colloidal substances removed by flotation were further confirmed. Adding cationic chemicals in papermaking process reduced led to decrease of sticky contaminants in water phase. Compared with the pulp sampled from the machine chest, less sticky substances were examined in the final papers, which meen that lots of sticky substances still remained in the water system or tend to deposit onto the machine parts.Effects of storage temperature on deinking of old newsprint and sticky contaminants in the deinked pulps were studied. Furthermore, deinking chemicals dosage and flotation time were investigated via the orthogonal experimental design, and factors influencing deinking process and stickies behaviors were discussed. Results showed that the storage temperature affected significantly the deinking process and stickies content. ONP stored under -10â—‹C gave good deinking performance. More macro stickies and less CS in DIP were found for the ONP stored under 20â—‹C, while less macro stickies and more CS for samples stored under -10â—‹C.