Hexenuronic acid contents of Eucalyptus globulus kraft pulps: variation with pulping conditions and effect on ECF bleachability.Application: The results of this research can be used in the control of hexenuronic acid formation in hardwood kraft pulp mills A pulp mill is a manufacturing facility that converts wood chips or other plant fiber source into a thick fiber board which can be shipped to a paper mill for further processing. . This study investigated the effect of pulping time and process parameters on the content of hexenuronic acid (HexA) in Eucalyptus eucalyptus (y  'kəlĭp`təs): see myrtle. eucalyptus globulus kraft pulps. Under selected standard pulping conditions, the amount of HexA in pulps increases during cooking. We tentatively attributed this behavior, significantly different from that of softwood softwood Timber obtained from coniferous trees (mainly of the pine and fir families). With the exception of bald cypress, tamarack, and larch, softwood trees are evergreens. pulps, to the milder conditions used in the pulping and/or to topochemical effects rather than to differences in the chemical structure of the glucuronoxylans from hardwoods and softwoods. As far as the kraft process kraft process Chemical method for producing wood pulp using caustic soda and sodium sulfide as the liquor in which the pulpwood is cooked to loosen the fibres. The process (from German kraft, “strong”) produces particularly strong and durable paper; another parameters are concerned, for the same kappa number The Kappa number is an indication of the lignin content or bleachability of pulp. It measures the amount of bleach required during digestion of a wood pulp (part of the process of paper making) in order to obtain a pulp with agiven degree of whiteness. (14, obtained by adjusting pulping time), the HexA content decreases when active alkali increases from 17% to 24% and increases with sulfidity in the range 15%-28%. We saw a decrease in the HexA content when temperatures rose from 150 [degrees] C to 170 [degrees] C and when liquor-to-wood ratio increased from 4 to 8. The variations observed are determined by two simultaneously occurring processes: HexA formation and degradation or dissolution with xylans. When the unbleached pulps with kappa number 14 were fully bleached by a DEDED sequence, we saw a general increase in chlorine dioxide chlorine dioxide, n an oxidizing agent used in oral care to decrease amounts of volatile sulfur compounds that may cause halitosis. consumption as the HexA of the unbleached pulp decreased. Daniel, Pascoal Note, Evtuguin, and Silvestre are with the University of Aveiro, Department of Chemistry, 3810-t93 Aveiro, Portugal Email Pascoal Neto at cneto@dq.ua.pt. |
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