Preparation And Mechanism Research Of Bamboo Pulp For Textile

Taking bamboo as a research object, this paper is to study the acid hydrolysis, Kraft pulping,and bio-enzymatic bleaching process of bamboo pulp, the relationship between pulp qualityindicators and after-processing properties. To investigate the influence of hemicellulose andlignin dissolution characteristics on pulp after processing performance, and provide a theoreticalbasis for large-scale use of bamboo pulp in textile material and theoretical studies.1. Chemical compositions and technical study of oxalic acid prehydrolysis process of MosobambooThrough the experiments, the chemical composition of Moso bamboo is as follows:cellulose content is45.38%, poly pentose content is21.93%, acid insoluble lignin content is22.62%, ash content is1.06%, moisture content is10.89%, the extract content of hot water is6.06%, the extract content of1%NaOH is26.70%, content of benzyl alcohol extract is7.10%.Single factor test results of oxalic acid prehydrolysis found that the process conditions ofacid prehydrolysis were as the followings: liquid ratio1:10, the pre-hydrolysis temperature170℃, prehydrolysis time20min and oxalic acid2.0%w/w. Based on the above results, afurther study through the response surface methodology found that the optimal conditions of acidprehydrolysis were as the followings: pretreatment temperature174℃, the pretreatment time26min, and oxalic acid3.0%w/w, the theoretical values of the cellulose content, the removal oflignin and the hemicellulose dissolution rate were63.91%,77.98%,96.67%, respectively.The moso bamboo raw material before and after prehydrolysis was analyzed with thescanning electron microscope (SEM), we found that a groove of fiber bundle surface after acidprehydrolysis become more obvious, fiber cell wall damage and fiber bundle outer layer becameloose. We could find that the infrared spectra did not change obviously through fourier transforminfrared spectrum (FTIR). We also found that the crystallinity of materials increased to65.12%from52.50%.2. Kinetics model research of oxalic acid prehydrolysisWe studied the kinetics of hemicellulose hydrolysis process in the high temperature and lowconcentrations of oxalic acid, and then obtained the xylose production rate constant (K1) and xylose degradation rate constant (K2), the expression as follow：k1=μ1[Ac]n1exp (-E1/RT)=2.232×1012[Ac]1.324exp (-11699.5/T)k2=μ2[Ac]n2exp (-E2/RT)=2.33×1010[Ac]0.5011exp (-16403/T)3. Technical study of moso in sulfate cooking processWe got better cooking program after optimization, the process conditions of acidprehydrolysis were as the followings: the cooking temperature155℃, holding time60min,18%NaOH,25%sulfidity, liquid ratio1:8, the starting temperature90℃, heating rate of4-5℃/10min. Under optimal cooking conditions, we could obtain the chemical components ofdissolving pulp such as cooking yield, alpha cellulose content, kappa number, average degree ofpolymerization, pH of the black liquor after cooking, cellulose content, pentosan content andacid insoluble lignin contents were31.36%,93.33%,21.07,935,12.33,92.98%,8.12%and1.37%, respectively.The moso bamboo raw material before and after cooking was analyzed with SEM, we foundthat bamboo material has been completely separated into single fiber, the micro fiber structureexposed on the surface of fiber, the groove of surface was shallow. We could find that theinfrared spectra change obviously through FTIR, We also found that the crystallinity of materialswas87.8%, which higher than the crystallinity after prehydrolysis.4. Delignification reaction process and kinetics study of Kraft cookingDelignification kinetics of cooking process showed major and residual delignificationstages, and were intended to first-order reaction, the activation energy of a chemical reaction intwo stages were93.97kJ/mol and85.73kJ/mol, respectively.Sodium hydroxide concentrationon delignification reaction order in the main delignification stage is0.347, and the residualdelignification stage is0.444. Sodium sulfide concentration on delignification reaction order inthe main delignification stage is0.003, and the residual delignification stage is0.010.Main delignification stage:-dL/dt=A·e-11303/T·L·[OH-]0.347·[S*]0.003Residual delignification stage:-dL/dt=A·e-10312/T·L·[OH-]0.444·[S*]0.0105. Technical study and mechanism research of bleaching bamboo pulp by xylanase andlaccaseThe optimal process conditions of xylanase (X) and laccase (L) are as follows: the optimumtemperature65℃, the effective pH5; The optimum conditions for single xylanase treatment: enzyme dosage1.4%, reaction pH5.2, the reaction temperature60℃, bleaching time20min,pulp concentration8%, liquid ratio l:10; The optimum conditions for single laccase treatment:enzyme dosage1.4%, reaction pH5.0, the reaction temperature65℃, bleaching time25min,pulp concentration8%, liquid ratio l:10; the optimal process conditions of (L+X) are as follows:xylanase dosage0.5%, laccase dosage0.4%, pulp concentration8%, bleaching time20min, thereaction temperature65℃, liquid ratio l:10;We studied the whiteness, Kappa number and viscosity after bleaching with five differentenzyme systems, and then found that the bleaching effect was good through (L+X), LX and XL,bleaching effect of (L+X) was best, which showed that compound enzymes could improve theeffect of bleaching.This paper analyzed bamboo pulp and waste water before and after bleaching by usingultraviolet (UV), FTIR, X diffraction and SEM, through the above testing, we found that theenzyme bleached bamboo reduced the lignin content, the lignin content of bleaching pulp with(L+X) decreased most, xylanase bleaching pulp decreased lowest; hexenuronic acid content hada certain decline after enzymatic bleaching treatment. We also found that the lignin structure hadnot changed significantly in the range of190-400nm through the ultraviolet absorption spectrum,and their absorption spectra were basically the same; From FTIR spectra, we could found thatthe infrared spectra very similar with and without the enzyme treatment, but the chromospheresgroup reduced after enzyme treatment.