Influence of the operating conditions in the acetone pulping of wheat straw on the properties of the resulting paper sheets

A central composite factor design was used to examine the influence of inde pendent variables in the acetone pulping of wheat straw (processing tempera ture, time, and acetone: concentration) on the yield of the resulting pulp, and on various physical properties of paper sheets (breaking length, stret ch, burst index. tear index and brightness) obtained from it. Equations that related each dependent variable to the different independent variables were obtained, and these reproduced the experimental results for the yield, breaking. stretch, burst index and brightness obtained at tempe ratures, times, and acetone concentrations over the ranges 140 180 degreesC . 60-120 min and 40-80% respectively, with errors less than 20%. Obtaining the optimum breaking length, stretch, burst index and tear index for the paper sheets (3456 m, 1.42%, 1.36 kN/g and 3.86 mNm(2)/g, respectiv ely) entails using a high temperature: the processing time and acetone conc entration only influence stretch, optimization of which requires using a sh ort time and a low concentration. The optimum brightness (30.44%) is achiev ed with a low temperature. a short time and a medium acetone concentration. In order to minimize losses of solvent during its recovery and recycling wh ile ensuring acceptable levels of the properties of the paper sheets, a hig h temperature, a low acetone concentration and a short time can be used; th e brightness level thus obtained is only 10% lower than the optimum value. (C) 2001 Elsevier Science Ltd. All rights reserved.