Study On The Process Technology For Manufacture Of Lyocell Dissolving Pulp From Neosinocalamus Affinis

Tencel is known as the green and environmentally friendly fiber in the 21st century.At present,lyocell dissolving pulp is mainly prepared from wood or cotton linters.China is rich in bamboo resources,in order to explore the possibility of preparing lyocell dissolving pulp from bamboo,we conducted a study on the preparation of lyocell dissolving pulp by pre-hydrolysis kraft method,discussed the influence of pre-hydrolysis process on the chemical composition of Neosinocalamus affinis,and studied the effect of pre-hydrolysis kraft cooking on the pulp quality such as yield of screened pulp,pulp kappa number,Tappi viscosity and alkali solubility have determined the process of pre-hydrolysis and kraft cooking.Finally,two-stage oxygen delignification and D₀E_pD₁D₂ ECF bleaching process and acid treatment,are used to prepare the pulp that meets the quality requirements for lyocell dissolving pulp.The results showed that Neosinocalamus affinis contains 74.31%holocellulose,53.64%cellulose（nitric acid ethanol method）,24.70%lignin and 20.67%hemicellulose,which makes it suitable for manufacturing dissolving pulp.Using pre-hydrolysis single factor experiment and design orthogonal experiment of kraft cooking process,The optimum pre-hydrolysis process conditions are as follow:hydrolysis temperature of 168℃,time of 120 minutes,liquor to material ratio of 4:1;The optimum kraft cooking process conditions are:effective alkali charge of 14.5%（base on Na₂O）,sulfidity of 25%,cooking liquor to material ratio of3.5:1,cooking temperature of 165℃,time at the cooking temperature of 110 minutes.Under the above pre-hydrolysis kraft cooking condition,the brown pulp has kappa number of 12.84,screen yield of 33.85%,Tappi viscosity of 34.00 m Pa·s,alkali solubility:S18 of 1.43%and S10 of 3.30%.The brown pulp was conducted with two stage oxygen delignification and D₀E_pD₁D₂ ECF bleaching process and acid treatment.Consequently,the bleached pulp has viscosity of 18.52 m Pa·s,alkali solubility:S18 of 1.45%and S10 of 3.34%,ash content of0.13%,iron content of 26.3 ppm and brightness of 89.42%.The effects of acid treatment and enzyme treatment on the quality of lyocell dissolving pulp were studied.The enzyme treatment used glutaraldehyde as the cross-linking agent,the immobilized enzyme formed by cellulase and sodium alginate,The optimum reaction temperature and p H of the immobilized enzyme was 50℃and 5.5 respectively.Under this conditions,4U/g of immobilized enzyme（relatively dry pulp）is reacted with the bleached pulp,the Tappi viscosity of treated pulp can be reduced from 18.52 to 13.77 m Pa·s.The process conditions of acid treatment is soaking temperature of 80℃,soaking time of 60minutes,p H of 2 to 3,pulp concentration of 5%,and sodium hexametaphosphate of 0.5%.The lyocell dissolving pulp that meets the quality requirements hasα-cellulose content of93.28%,DP of 610,brightness of 90.10%,ash content of 0.01%,DCM content of 0.03%,iron content of 1.88 ppm,copper content of 0.91 ppm,copper number of 0.83.