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Viscose rayon fibre

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Viscose rayon fibre

  2. 2. Introduction: 2 It is oldest regenerated cellulose fibre. It is biodegradable & renewable polymer. Comman sources wood pulp & cotton lint. Highly purified wood pulp consists of of 90-95% cellulose called chemical cellulose & dissolving pulp. The process used to make viscose either continuous or batch process. INDIAN INSTITUTE OF TECHNOLOGY, DELHI
  3. 3. PROCESS TO MAKE ORDINARY RAYON: 3 Cellulose pulp 13”X18” or 20X30” & cellulose :87-98% are Steeping vertically stacked in 3”-6” apart to each other. & tank contain 17-18% NaOH. (C6H10O5)n + nNaOH -- (C6H9O4ONa)n + nH2O Shredding To make cellulose in fluffy crumbs by mechanical action Ageing De-polymerization Add CS2: 32-35%,1-3 h,20-30 0c 1-4 rev. Xanthation (C6H9O4ONa)n + nCS2 ----> (C6H9O4O-SC-SNa)n INDIAN INSTITUTE OF TECHNOLOGY, DELHI
  4. 4. CONTINUED... 4 Dissolution Add 4-6% NaOH +agitators and total sulphr-2 to 2.5% Storage at 15-25 0 c for 1-3 days. In this time redistribution of xanthate take place. Ripening (C6H9O4O-SC-SNa)n + nH2O ---> (C6H10O5)n + nCS2 + nNaOHFiltration & Blending Remove undissolved material, bubble air INDIAN INSTITUTE OF TECHNOLOGY, DELHI
  5. 5. CONTINUED… 5 H2SO4-8-10% Spinning Na2SO4-16-24% ZnSO4-1-2% (C6H9O4O-SC-SNa)n + (n/2)H2SO4 --> (C6H10O5)n + nCS2 + (n/2)Na2SO4 Spinning speed may be high as 120m/min Spinning Bath NeutralizationDrying & Winding INDIAN INSTITUTE OF TECHNOLOGY, DELHI
  6. 6. PROPERTIES OF RAYON: 6 Tenacity ranges between 2.0 to 2.6 g/den when dry and 1.0 to 1.5 g/den when wet. Wet strength of the fibre is of importance during its manufacturing and also in subsequent usage. Modifications in the production process have led to the problem of low wet strength being overcome. Dry and wet tenacity extend over a range depending on the degree of polymerization and crystallinity. The higher the crystallinity and orientation of rayon, the lower is the drop in tenacity upon wetting. INDIAN INSTITUTE OF TECHNOLOGY, DELHI
  7. 7. CONTINUED: 7 Thermal properties: Viscose rayon loses strength above 149 C; chars and decomposes at 177 to 204 C. It does not melt or stick at elevated temperatures. Chemical properties: Hot dilute acids attack rayon, whereas bases do not seem to significantly attack rayon. Rayon is attacked by bleaches at very high concentrations and by mildew under severe hot and moist conditions. Prolonged exposure to sunlight causes loss of strength because of degradation of cellulose chains. Abrasion resistance is fair and rayon resists pill formation. Rayon has both poor crease recovery and crease retention. INDIAN INSTITUTE OF TECHNOLOGY, DELHI
  9. 9. SPINNING WITH MODIFIERS: 9 Modifiers enhance the action of zinc in the spinning bath without effecting the viscose. Formation of semipermeable membrane by the combined action zinc ions by the product trithocarbamate ions viscose & modifiers and makes an barrier which retards the diffusion of both Zn+ & H+. So the acidification boundary shift further away from the nozzle in the presence of modifiers. MODIFIERS Tertiary amine Quaternary ammonium salt Polyoxyalkylene derivative Polyoxyhydroxy polyamide Dithiocarbamates INDIAN INSTITUTE OF TECHNOLOGY, DELHI
  10. 10. CONTINUED: 10Tyre yarn-A viscose solution of viscosity 100 poise containing modifiers 1-3% byweight of cellulose and with a CS2 content of 40% is spun underripe intoa aqueous spinning bath containing –H2SO4 8-10%Na2SO4 16-24%ZnSO4 6%The spin bath temperature is kept around 550c and the spinning speed isbetween 40 and 60 m/min. The stretch applied is 75-125% INDIAN INSTITUTE OF TECHNOLOGY, DELHI
  11. 11. CONTINUED: 11Modified high wet-modulus yarns- The condition of viscose solution and spinning bath composition aregenerally similar to those tyre yarns. Spinning bath temperature 350c is kept lower because it gives more deformable gel necessitating a slower spinning speed 20-40 m/min The result is that gel fibres are stretched at an earlier state of the gel dehydration and decomposition when the gel is more plastic and can be stretched more(125%-150%).Polynosic fibre-It is similar to rayon process but with-outing having the step ofageing and ripening stage, with dilute acid concentration & zinc sulphate. Its having the high crystallinity & orientation, ,chemical resistance ,high wet modlus and more dimension stable. INDIAN INSTITUTE OF TECHNOLOGY, DELHI
  12. 12. CONTINUED: 12 Spinning bath- H2SO4-2-3% Na2SO4-4-6% Temp-250c Spinning speed-20-30m/min Stretch-150-300% - Crystallinity(%) Birefringence Standard 45.2 0.027 Viscose Tyre yarn 41.5 0.037 Polynosic 55.2 0.046 Super high wet modulus rayon-By adding 1% formaldehyde to spin bath . Stretch - 500-600% INDIAN INSTITUTE OF TECHNOLOGY, DELHI
  13. 13. Fibre variant for improvrd bulk & hsndle-: 13 TO produce high performance crimped fibres where the bulk is due to the interaction between the fibres, creating bulk in resultant yarns and fabric. The second approach has been to produce an inherently bulky fibre using an inflation technique during fibre production. Composition Typical range(%) Cellulose 7-7.5 NaOH 6-7.5 CS2 30-32 Modifiers: Dimetylamine .8-1.5 Polyethylene glycol .8-1.5We can produced different types of fibres-1. High performance crimped fibres.2. Super absorbent fibres.3. Flame retardant fibres. INDIAN INSTITUTE OF TECHNOLOGY, DELHI
  14. 14. Incorporation of carbon in viscose fibre: 14(a) Incorporation of carbon black for antistatic properties- Electrically conductive carbon is used for the production of electrically conductive fibre. For the production of the electric conductive fibre a slightly alkaline electric conductive carbon black with a particle size 20 nm is dispersed in water and mixed in viscose solution prior to spinning.(b) Incorporation of graphite.-Incorporating 40% of lubricating graphite with a purity 99.5% into viscose yields fibres with excellent lubricating properties which as packing and sealing for crankshafts. Packings from graphite containing viscose fibres may be used to a temperature of 180-2000c.They are stable in the Ph range 5-9 . INDIAN INSTITUTE OF TECHNOLOGY, DELHI
  15. 15. ALTERNATIVE METHOD TO DISSOLVE TO CELLULOSE: 151. N-Methylmorpholine N-Oxide And Water-1. It is the best solvent to dissolve viscose fibre.2.Its having strong oxidant property due to which it candissolve cellulose. INDIAN INSTITUTE OF TECHNOLOGY, DELHI
  16. 16. DOPE PREPAETION : 16Its having high potential to dissolve cellulose up to 50%. Mixture transfer in air Disadvantage- 1.During the dissolving step time tight vessel and temp. are maintained properly otherwise thermal degradation & explosion takes place. Generally temp. is around 1300c. Mix & stirred 2. .If the temp. is goes above 150 0 c ,DP of cellulose goes down for this we add some phenolic oxidant .It stabilize the solution and finally oxidize the colour compound.Heat it up to 130 O C For 30 min INDIAN INSTITUTE OF TECHNOLOGY, DELHI
  17. 17. CONTINUED: 172. . N-N Dimethyl acetamide and lithium chloride-1. It is another solvent which dissolve cellulose. It directly linked with very high reproducible.2. It was observed that fibres from wet spinning process exhibited superior properties.3. It makes an complex with OH-group of cellulose & help to dissolve cellulose. solution is much stable in nature. It is stable few years in room temperature. INDIAN INSTITUTE OF TECHNOLOGY, DELHI
  18. 18. CONTINUED: 18Dope preparation- DMAc + Cellu-OH Of mixture Distillated at 165 0c In nitrogen atmosphere,30 min Reduce temperature Stirring continuously at 80 0c for 40 min Solution is ready at 100 0c +Licl INDIAN INSTITUTE OF TECHNOLOGY, DELHI
  19. 19. CONTINUED:3. Ionic liquid 19Salt that melt at temp. below 1000c called as ionic liquid or green solvent. Properties-1. Chemically & thermally stability. 2.Non-flammability Generally contain imidazoloium, pyridinum or organic ammonium cation. The anion could be chloride ,bromide. Room temp. have more stronger complex. INDIAN INSTITUTE OF TECHNOLOGY, DELHI
  20. 20. CONTINUED: Cellulose can be dissolved, solubility of cellulose and its properties can be easily 20 controlled by selection of ionic liquid compound. At high chloride concentration is responsible for breaking for hydrogen network . Thus allowing to dissolve cellulose. Dope solution can be easily precipitated by the addition of water, ethanol or methanol The regenerated cellulose is hardly degraded and has almost the same degree of polymerization and polydispersity as the initial cellulose. The ionic liquids can be recovered and reused by various methods, such as evaporation, ionic exchange, reverse osmosis and salting out. INDIAN INSTITUTE OF TECHNOLOGY, DELHI
  21. 21. Ammonia /ammonium thiocyanate : 21Advantages-1. It has an excellent dissolving power as a solventfor cellulose.2.Low cost and readily available.3.Due to boiling solvent 700c ,as a result it can handled easily.4. No degradation of cellulose.5.Solvent preparation (NH3/NH4SCN 24.5/75.5) is very simple. INDIAN INSTITUTE OF TECHNOLOGY, DELHI
  22. 22. Dope preparation: 22 Require amount of cellulose +Ammonia +Ammonium thiocyanate Mix it Place it and mixed with hand & homogenized mixture pass The bag place in through shearing Increase temperature up cool place at -33 force at room to 40 0c to make solution 0c for few mins temperature INDIAN INSTITUTE OF TECHNOLOGY, DELHI
  23. 23. Amine salt: 23 Hydrazine Ethylenediamine Two component system (amine salt) consisting of hydrazine or ethylenediaine and various Thiocyanate salt such as LIScN, NaScN or KScN that dissolove cellulose pump. A high concentration 40-50% salt is generally required to obtain high concentration up to 18-20% spinning dope. INDIAN INSTITUTE OF TECHNOLOGY, DELHI
  24. 24. Dope preparation : 24 Solvent +cellulose in polyethylene bagPlace at -10 0c for few hours Apply shearing Increase force for 30 min temperature to dope up to 50 0c preparation INDIAN INSTITUTE OF TECHNOLOGY, DELHI
  25. 25. CONTINUED: 25  Ethylenediamine/KSCN System is the best solvent. INDIAN INSTITUTE OF TECHNOLOGY, DELHI
  26. 26. Development in process technology &process 26 chemistry: Difficulties-1. Old batch-wise process to continuous or semi-continuoussystem. In the batch wise process the sequence of steeping ,pressingand ageing took up to 40 hr. to produce alkali cellulose.2.Difficulties in ensuring contact temp. and equal ageing time,because a large no. of bins involved ,frequently resulted in a variabledegree of polymerization in the resultant viscose.Process- 1. In the modern plants bales of wood pulp are auto-matically fed into continuously sulrry.2. By the use of catalyst and elevated temp during ageing havereduced to time 4-5 hr.3.Xanthation process has been improved with the use of wet churns.Inwhich both xanthation and mixing carried out. INDIAN INSTITUTE OF TECHNOLOGY, DELHI
  27. 27. CONTINUED: 27 4.More recently the introduction of back flush filters with non-woven metalscreens has improved the filtration efficiency with the new non woven metalscreens the filtration amount has increased 50 fold. Thus the filtration sizecould be decreased.5. Completely automatization.Process chemistry- Reduction in chemical used such asCS2,NaOH and H2SO4Process-SINI process-Its also known as double steeping processoperation of aged alkali cellulose at lower alkali concentration(10-12%).A second steeping after ages reduces the amount offree alkali in the crumb with out changing the bound alkali. Thisreduces the formation of by-product and improves distributionof xanthate group to get a stable viscose INDIAN INSTITUTE OF TECHNOLOGY, DELHI
  28. 28. CONTINUED: 28Other process-1.Activation of cellulose with liquid ammoniaprior to xanthation also reduces CS2 consumption by asmuch as 33%. 2. Xanthation in the presence of surfactants like Berol spindecreases CS2 consumption without effecting the quality ofrayon produced.The addition of urea to the steepingsolution result in change viscosity of viscose, the ripeningtime decreases and a high degree of xanthate substitutionis obtained. It is presumed that compex with the alkalicellulose is formed which control the side reactionsoccurring during xanthation process. INDIAN INSTITUTE OF TECHNOLOGY, DELHI
  29. 29. CONTINUED: 29 A reduction in viscosity of viscose allow for an increases in α-cellulose content & leads to reduction in consumption of H2SO4 & also less amount of energy is required for transport, filtration.Advantages-1. This process yield a 30% reduction in CS2 useage,reducing CS2 emission.2.It is claimed that even interior-grade pulp can be used with this processto yield a good quality of viscose fibre.3.Due to removal of low molecular weight fractions. In the secondsteeping as well as increased rate of swelling of alkali cellulose whichincreases the reactivity to CS2 during xanthation with this process ahigher CS2:NaOH ratio(9:4.5) can be used in viscose solution which resultin a substantial reduction in H2SO4. INDIAN INSTITUTE OF TECHNOLOGY, DELHI
  30. 30. Conclusion: 30 Development in process technology & process chemistry are much environment friendly Polynosic fibre show high crystallinity ,high resistant ,high dimension stability. By different solvent ,spinning specifications ,modifiers . We can make end use product. Solvent is very costly so need to recycle it. Ethylenediamine/KSCN System is the best solvent. INDIAN INSTITUTE OF TECHNOLOGY, DELHI
  31. 31. References: 311. Spinning of cellulose from N-methyl morpholine N-oxide in the presence ofadditives, polymer 1990,vol 31,march.2. Structure formation of regenerated cellulose materials from NMMO solutions,progress in polymer science 26(2001).3.Novel cellulose solvent system and dry jet wet spinning of cellulose ED/KSCNsolution, by hyun jik cel (thesis)4. www.google.com5. Life cycle assessment of man-made cellulose fibres, lenzinges berichte88(2010)5. Modified polynosic fibres.6. Handbook of fibre chemistry, M lewin & E.M pearce.7. V.B Gupta & V.K Kothari ,Manfacturing of fibre technology 481-513. INDIAN INSTITUTE OF TECHNOLOGY, DELHI