Study Of Cellulose Acetate From Eucalyptus

Cellulose acetate is used widely,its raw materials is cotton of high-cellulose content or senior coniferous wood pulp,which is needed to import from abroad.Therefore,the research and development of wood pulp become the key issues of sustainable development of cellulose acetate,Eucalyptus is an important fast-growing hardwood species,which has importance to ease the cellulose acetate industry in China.Eucalyptus is studied as raw materials in this paper,including pulping,bleaching,xylanase and alkaline purification process,the product meet the requirements of cellulose acetate pulp,and then activation,acetic anhydirde,hydrolysis process and its mechanism explore.The main experimental results:(1) The pulp is cooked by means of KP+AQ,conditions:alkaline 17%(Na₂O),sulphidity 16%,AQ 0.05%,liquid ratio 1:4,idling about 30 min,heating to 130℃within 90min;then warming up to 170℃in 90min,holding temperature about 60min.(2) In order to increase brightness without causing environmental pollution,it's needed to research the conditions of D₁ED₂ conventional bleaching,the amount of chlorine must be controlled within 3.6% at D₁ stage;in order to improve a-cellulose content and degree of polymerization,alkaline conditions is needed more stronger to remove the hemicellulose.But it is not feasible to increase a-cellulose content by increasing the amount of alkaline.Eucalyptus wood pulp bleaching conditions for cellulose acetate: D₁,the amount of chlorine 3.6%,70℃,90 min,plup consistence 10%,pH 3.5;E paragraphs NaOH 2.0%,75℃,60 min,pulp concentration 10%;D₂,the amount of chlorine 0.9%,70℃,90 min,plup consistence 10%,pH 3.5;P,the amount of NaOH and H₂O₂ are the same amount of 2.5%,70℃,90 min, plup consistence 10%.(3) Pulp's xylanase purification conditions:enzyme dosage 120 IU/g,60℃,time 2h,plup consistence 3%,pH 6.0.Alkali purification,NaOH can not only remove part of hemicellulose,also dissolve some short-chain cellulose,when the alkali consistence is 4%,the degree of polymerization 1163,brightness 90.0%,a-cellulose content 96.78%,cellulose acetate pulp achieve international standards.(4) Scanning the pulp before and after purification treatment by 1R.It's found that:the chromophoric group and color auxochrome group,such as the C=O stretching vibration(1058cm^-1), lignin-alkyl ether-based C-O-C stretching vibration(1164cm^-1),aryl-alkyl ether bond(1240cm^-1), lignin carbonyl stretching vibration C=O(1637cm^-1),lignin aryl ring vibration(1430 cm^-1),their absorption peak intensity has weakened after purification,and this is why the pulp's brightness increased after purificationt.(5) The activation of eucalyptus pulp's conditions:time 3.0 h,temperature 50℃,the amount of acetic acid 500%;acetic anhydride conditions:the amount of acetic anhydride 400%,the amount of catalyst sulfate 7.5%,temperature 60℃,time 2.0 h;the hydrolysis conditions:80%acetate content, temperature 60℃,degree of substitution of CA is 2.51.(6) Scanning pulp before and after activation by means of X-ray diffraction and IR.The activation is just a physical process,change the crystalline structure of cellulose,making available district increased,more hydroxyl can be reached by acetic anhydride.The activation processing is a preparation for next step,there is no obvious chemical reaction occurred.(7) Scanning the CA by IR.1752cm^-1 C=O stretching vibration,3348 cm^-1 -OH stretching vibration,which intensity decreased significantly,it's proved that the product is CA.X-ray diffraction of CA:hydrogen bonds weaken,the introduction of acetic group make crystal structure damaged to a certain extent,which result in the reduction of cellulose crystallinity.