Síntesis de carboximetilcelulosa (CMC) a partir de pastas de plantas anuales

Identificador:  TDX:285

Handle: https://hdl.handle.net/20.500.11797/TDX285

Autors:  Barba Pacheco, Claudia

Resum:
Keywords: waste lignocellulosic materials, poplar, pine, wheat straw, annual plants, abaca, sisal, jute, linen, Miscanthus sinensis, sugar cane, henequen, fast soda/AQ pulps, IRSP pulps, carboxymethylcellulose, rheological behavior, degree of substitution.<br/><br/>In this manuscript we describe the synthesis and characterization of carboxymethylcellulose (CMC) samples from different lignocellulosic residual and non-wood materials. We also describe how the condition of the raw materials affects the preparation and final properties of the CMCs produced. The production of carboxymethylcellulose from these materials is an important contribution because, currently, it is produced from cotton linters and pine and eucalyptus wood.<br/>The CMC samples were prepared from three kinds of cellulose pulps: <br/>&#61623; Soda/anthraquinone bleached pine, poplar and wheat straw pulps with cooking residence times ranging from 3 to 90 min.<br/>&#61623; Steam exploded Miscanthus sinensis, sugar cane and henequen pulps cooked by IRSP (Impregnation Rapid Steam Explosion Process).<br/>&#61623; Commercial bleached paper pulps cooked by the soda/anthraquinone process of abaca, sisal, jute and linen.<br/>High purity carboxymethylcellulose was obtained by the etherification Druvacell&#61650; process on a laboratory scale, always under the same conditions and with the same chemical amounts.<br/>The final purified products were characterized in terms of their degree of substitution (DS), purity and solubility in concentrated NaOH, CMC intrinsic viscosity &#61531;&#61544;&#61533; in 0.1M NaCl solutions, molecular weight and rheological behavior of CMC samples at different concentrations.<br/>We found that the DS depended on the raw material morphology and properties and not on the cooking temperature of the pulp source. The method we used for the etherification reaction yielded CMCs whose degree of substitution was close to 1 after one etherification reaction, and around 2 when a second etherification reaction was performed at the same conditions. Miscanthus sinensis and sugar cane were the only exceptions because they yielded CMCs with a DS of around 0.75 and 1.45 after one and two etherification treatments. <br/>All CMC samples had purities of over 98%. The molecular weights and the rheological behavior of the CMC solutions were directly related to the viscosity of the pulps. Pulps of lower viscosity therefore produced CMCs whose rheological behavior was similar to Newtonian behavior. On the other hand, the pseudoplastic behavior was obtained from pulps of higher viscosity.<br/>The rheological characterization of the CMC samples shows the viability of obtaining carboxymethylcellulose from non-conventional materials whose characteristics are different from those obtained from common materials such as wood or cotton. These new materials have great potential for producing cellulose derivatives with novel characteristics like temperature stability that make them suitable for specific and tailor-made industrial applications. <br/>Overall, our results show that carboxymethylcelluloses can be obtained from non-conventional materials having similar characteristics to commercial CMC. We also confirm the production of CMC from rapid soda/AQ and IRSP pulps, being posible to extend this study for other cellulose derivatives of industrial interest.