Obtainion and characterization of absorbent materials throught carboximelation of etanol/water pulp non fiber fraction sugar cane bagasse. / Obtenção e caracterização de materiais absorventes através de carboximetilação de polpa etanol/água de medula de bagaço de cana de açúcar.

AUTOR(ES)
DATA DE PUBLICAÇÃO

1996

RESUMO

This work describes the use of ethanol / water pulps of pith in a study aiming the obtention and characterization of substantially insoluble carboxymethylcellulose for application as an absorvente material. In a typical experiment the carboxymethylation reaction of bleached ethanol / water pulp occurred at 80°C for 4 hours in isopropanol/ water suspension 1 : 8 (w/w) employing a cellulose / sodium hydroxide / monochloroacetic acid molar ratio of 1.0/5.4 / 8.8. Characterizations were made through the determinations of the presence of characteristic functional groups; degree of substitution (DS); solubility in pure water and alkaline aqueous solution; water and saline aqueous solution retention capacity; morphology and thermal stability of the obtained products. Infra-red (i.r.) and nuclear magnetic ressonance (NMR) spectroscopies; scanning electronic microscopy (SEM); thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were employed for these characterizations. The material with the best absorbent characteristics was obtained through the application of the condition above described for the carboxymethylation reaction. This is a very insoluble product (S IDO <20/0) with a much higher water retention capacity than unreacted pulp employed as raw material. Other eight products were prepared through the application of different concentrations of monochloroacetic acid and variable reactions times. AlI products manifested the polyelectrolyte effect, but their water retention capacities seem to depend on the degree of substitutions in a complex way. Water retention capacities of the products of this work seem to be the result of a compromise among the parameters of the carboxymethylation reaction, the content and distribution of ionic groups and the degree of crosslinking. From our results it cannot be concluded if the materials correspond to physically or covalently crosslinked polyffiericchains since the occurrence of ester bonds as crosslinkers can not be discarded, but its detection in the infra-red spectra is difficult as a consequence of the extensive superposition of bands in the region of interest. Although the use of conventional sources of cellulose in conditions similar to those described here result in products of superior quality we believe that pith can be a good altemative raw material for the obtention of carboxyffiethyl ceIlulose with absorbent characteristics. In Brazil it is available as a very abundant and low cost raw material derived from the industries which process sugar cane for the production of ethanol and sugar and its utilization in place of wood pulps may also represent ecological advantages as forest preservation will be favoured. Finally it is worthwhile to remember that the quality of the products also depends on the raw material characteristics, mainly the degree of polyffierization of the cellulose obtained after pulping. So the use of the other pulping and bleaching processes which minimize chain degradation wiIl certainly result in better pulps from pith and as a consequence materials with better absorbent characteristics will be prepared.

ASSUNTO(S)

carboximetilcelulose materiais absorventes medula de bagaço etanol/water pulp non fiber fraction bagasse absorbent materials polpa etanol/água carboxymethylcellulose

ACESSO AO ARTIGO

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