Influence of the chemical composition of the pulp kraft bleaching by the sequences ODHT(PO)D and ODHT(PO)DP on the process of brightness reversion / Influência da composição química da polpa kraft branqueada pelas seqüências ODHT(PO)D E ODHT(PO)DP no processo de reversão de alvura

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

In this work a study on the chemical composition of pulps of Kraft cellulose whitened before and after the test of dry reversion was carried out aiming to know the processes of reversion of whiteness. Samples of pulps were analyzed, given by the industry, collected after each one of the stages of whitened through the sequence of ODHT(PO)D. It was also done the analyses of water which is used in the same industry to dilute the whitened pulp, which goes through drying in the RAUMA machine before going to the commercialization. The analyses of that water had as an objective to evaluate the possibility of contamination of the pulp through constituents that came from the washing water. It was performed, in laboratory, the whitened using the sequences ODHT(PO)D and ODHT(PO)DP, from the pulp pre- deslignified (pré-O2) given by the same industry. The quantities of reagents employed in each stage of the whitening were established in order to obtain final whiteness (88% ISO) equivalent to that reached in the industry. The pulp obtained after each stage of whitening was submitted to sequential extraction with dichloromethane and acetate de etila. The extracts were analyzed through spectroscopy techniques at the UV-visible, infrared and through gas chromatography joined to mass spectrometry (CG-EM). The analyzes of the extracts through spectroscopy in the visible- UV were little significant to compilation of the data concerned to the causes of the reversion. The spectra in the infrared obtained to the extracts of the reverted and non-reverted pulps were very similar, and showed in all cases bands of typical absorption of carboxylic acids, alcohols and compounds of aliphatic nature. The analyses of CG-EM led to identification of fatty acid, acid of low molecular mass, alcohols, steroids, hydrocarbons, carbohydrates and furanicos compounds. The acid butanodioic, the 2-furancarboxylic acid, carbohydrates and derivates were identified in higher quantities in the reverted samples. This constituents can be related to the reversion process of whiteness. The pulps referents to the later stages of whitening were analyzed through the pyrolysis technique joined to gas chromatography and to the spectrometry of mass (Pi-CG-/EM). Through pyrolysis was possible to identify some substances that werent extracted with the used organic solvents. Aromatics compounds were identified, mainly derivates phenolics, possibly from lignin and/or extractives from wood that persisted along the whitening. Those fragments of phenolic compounds possibly were polymerized and/or linked to cellulose chains, so that extraction with organic solvent became unable.

ASSUNTO(S)

peróxido de hidrogênio Água analysis branqueamento quimica organica bleaching hydrogen peroxide dióxido de cloro polpa de madeira análise chlorine dioxide water wood pulp

ACESSO AO ARTIGO

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