Preparation And Properties Of Hemp Based Lyocell Fiber

Lyocell fiber is known as the green fiber of the 21st century because of its simple process,high production efficiency and environmental protection.Lyocell method has a high requirement for pulp quality,which makes the pulp needed for Lyocell method to prepare regenerated cellulose fiber mainly come from import at present,which also limits the industrialization development of Lyocell fiber.Seed use marijuana for its seeds,crops grow faster but the bast was a large number of abandoned,burned it may cause bad effects to the environment,thus to explore the development and utilization of hemp hemp seed leather for Lyocell fiber theory and market value.In this paper,the composition and structure of hemp fiber were analyzed,and the pulp for Lyocell fiber was made into standard by a series of treatments,and then used for the preparation of Lyocell fiber to realize the high-value utilization of hemp phloem for seed.The research contents of this paper are as follows:(1)Lyocell pulp was prepared from hemp fiber by controlling polymerization degree and removing iron.The influence of hydrothermal conditions on the degree of polymerization,crystal shape and crystallinity of pulp was studied.The results showed that the reaction conditions of alkali degradation of pulp were harsh,and it was necessary to use high concentration alkali for a long time under high temperature and high pressure.When the concentration of Na OH exceeds 10%,the cellulose crystal will change from cellulose type I to cellulose type II.The polymerization degree of hemp fiber was 647 and the crystallinity was79%when Na OH concentration was 10%,hydrothermal temperature was 170℃,bath ratio was 1:35 and reaction time was 2 h,which met the requirement of the polymerization degree of Lyocell pulp.Compared with alkali treatment,acid treatment conditions are more mild.When the concentration of oxalic acid was 0.6%,the hydrothermal temperature was 140℃and the hydrothermal time was 90 min,the polymerization degree of hemp fiber could be reduced to 606 and the crystallinity was 86%.When the concentration of formic acid is 10%,the hydrothermal temperature is 140℃and the hydrothermal time is 90 min,the polymerization degree of hemp fiber can be reduced to 638 and the crystallinity is 85%.(2)Using degraded hemp pulp as raw material,the optimum technological conditions for reducing iron content in hemp pulp by acid treatment and chelating agent treatment were studied.The results showed that the optimal conditions of oxalic acid treatment were p H 2,reaction time 60 min and reaction temperature 60℃,under which the content of residual iron in pulp was 10.4 ppm.The use of oxalic acid and other organic acids can reduce the damage to the fiber microstructure,and the removal effect is better,because the iron ion in pulp is replaced by H~+ionized by oxalic acid and then complexed by oxalate,promoting the balance of the reaction movement,so that more iron is removed.In the treatment of pulp with chelating agent DTPA,when DTPA concentration was 1.2%,reaction time was 50 min and reaction temperature was 80℃,the residual iron content in pulp was 14 ppm.(3)Lyocell fiber was prepared by dry spray wet spinning process using hemp pulp after degradation and iron removal as raw material,and the spinning process conditions with the best mechanical properties were found by regulating the concentration of spinning solution and solidification bath temperature.The results show that when the concentration of spinning solution is less than 14%,the breaking strength and initial modulus of hemp Lyocell fiber increase with the increase of the concentration of spinning solution.When the concentration of spinning solution is too high,the spinnability becomes worse and the mechanical properties decrease.The elongation at break decreased with the increase of the concentration of spinning solution.In the preparation of hemp Lyocell fiber,the mechanical properties are better when the concentration of spinning solution is 14%.With the increase of coagulation bath temperature,the breaking strength and initial modulus of hemp Lyocell fiber increased first and then decreased,and the elongation at break decreased gradually.The mechanical properties of fibers prepared at 20℃solidification bath are better.Lyocell,which was prepared under the best conditions,showed that the fiber had smooth surface and compact structure,and the cellulose crystal changed from type I to type II.