Preparation And Properties Of Spun-Dyed Lyocell Fiber

Lyocell fiber is called"green fiber"because of its pollution-free production process,solvent recovery and biodegradability.In addition,the Lyocell fiber has excellent physical and mechanical properties and good moisture absorption,as well as a unique smooth,soft feel and high wearable comfort,so the Lyocell fiber has developed rapidly in recent years in China and has good application prospects.In order to further expand the application of Lyocell fiber,it is very important to dye it.The conventional coloring methods produce excessive dyeing wastewater and cause environmental pollution,so spun-dyeing of Lyocell fiber is becoming a hot research topic.In this paper,two dyes,CI Reactive Blue 194 and Indigo,were used to prepare different Lyocell fibers by different dyeing processes.The composition,structure,apparent morphology and properties of dyed fibers were compared,and the following conclusions were obtained:Firstly,cellulose pulps were dyed with CI Reactive Blue 194.The absorbance of CI Reactive Blue 194 solution before and after dyeing was measured by UV spectrophotometer,and the color fixation rate of CI Reactive Blue 194 on cellulose pulp dyeing was calculated,and combined with the apparent color of dyed pulp,the optimal concentration of dyeing of CI Reactive Blue 194 for cellulose pulp was 3%（owf）.The structure and properties of the dyed pulp were characterized by FITR,XRD and TG,and the dissolution process of different cellulose pulp in 87%NMMO solution was then observed.The results showed that the chemical composition of pulp dyed with CI Reactive Blue 194 was changed,and the thermal weight loss of cellulose pulp was decreased,but the crystal structure was not changed and the dissolving property in NMMO was not affected.Further,dyed pulp blended with undyed pulp in different proportions was used to prepare spun-dyed Lyocell fiber with different concentrations of CI Reactive Blue 194,and the structure and properties were characterized by FITR,XRD,TG,SEM and polarized light microscopy,and the color properties as well as color fastness were tested according to industry standards.Finally,FITR and ICP were performed on the spinning coagulation bath obtained from spun-dyed Lyocell fiber.The results showed that the cross-linking of CI Reactive Blue 194 with cellulose macromolecules in the spun-dyeing reduces the fibrillation phenomenon and hinders the crystallization of Lyocell fiber,but increases their orientation and thus improves the mechanical properties of Lyocell fiber.In addition,CI Reactive Blue 194 also decreases the thermal weight loss of Lyocell fiber;the color depth of spun-dyed Lyocell fiber with CI Reactive Blue 194 is not as deep as the conventionally dyed Lyocell fiber with CI Reactive Blue 194 but it has higher color fastness to sunlight.The results of the coagulation bath analysis showed that the use of CI Reactive Blue194 in spun-dyeing of Lyocell fiber does not affect the recovery of NMMO solvent.By using the oxidation property of NMMO solvent,the Indigo cryptochromes were added to it for stirring and dispersion,and the Indigo particles were formed by the Indigo cryptochromes,and the particle size of Indigo was regulated by controlling the stirring speed and stirring time,and the particle size of Indigo was characterized by nanoparticle size and potential analyzer and scanning electron microscope.The average particle size of Indigo could be reduced to 587.8 nm by using magnetic stirring at 1700 r·min^-1and 30 min stirring time,and then the average particle size could be reduced to 222.3 nm after ball milling.In addition,the dyed pulp with Indigo was prepared by using cellulose pulp to absorb the Indigo cryptochromes directly,and furthermore,the spun-dyed Lyocell fiber was prepared by two dyeing processes:spun-dyed by dispersion dope coloring and dyed pulp blend with undyed pulp.FITR,XRD and polarized light microscope were used to characterize the chemical components and supramolecular structure of the Lyocell fibers and then the TG and fiber strength meter were used to characterize their thermal weight loss properties and mechanical properties,and their color properties and color fastness were tested according to industry standards,and the components in the spinning condensation bath obtained by coloring the original solution of indigo dye were characterized by infrared spectrometer.The results showed that the chemical composition of the spun-dyed Lyocell fibers with Indigo change,the crystal structures do not change,but the crystallinity increase,which improve the mechanical properties of the dyed Lyocell fiber;Indigo reduce slightly the thermal weight loss rate of Lyocell fiber but the overall effect is not significant;the spun-dyed Lyocell fibers have high sunlight and soap fastness;the Indigo is present inside and on the surface of Lyocell fiber.In addition,the Indigo does not diffuse into the spinning coagulation bath,and which does not affect the recovery of NMMO solvent.In summary,both the CI Reactive Blue 194 and Indigo are suitable for spun-dyeing of Lyocell fibers,and the colorfastness of the prepared colored fibers is high,and the mechanical properties are improved.In addition,CI Reactive Blue 194also helps to reduce the fibrilization of Lyocell fibers.The research results of this thesis have some guiding significance for the dyeing application of Lyocell fibers.