Wet spinning of acrylic fiber

Wet spinning is the oldest of the five processes. This process is used for polymers that need to be dissolved in a solvent to be spun. The spinneret is submerged in a chemical bath that causes the fiber to precipitate, and then solidify, as it emerges. The process gets its name from this "wet" bath.

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BAHIR DAR UNIVERSITY
Ethiopian Institute of Textile and Fashion Technology
“Manmade fiber Technology”
Title: Wet spinning of Acrylic fiber
Prepared By:-BerihunGashu(MSc in TC)
Submitted to:-Mr. AdaneH. (Assoc. Prof.)
June 2021 G.C.

2. Contents
2
oIntroduction
oTheoretical background
oWet spinning of Acrylic fiber
oWorking principle
oParameters of wet spinning of acrylic fiber
osummery
oReferences

3. 3
Introduction
Oldestspinningmothedfromotherprocesses.
Non-volatilesolventforpreparation,
Non-solventsforcoagulation,
Submergedinacoagulationbath
Acrylic,rayon,aramid,modacrylic,andspandex.
Acrylonitrile

4. 4
Conti…
volatile solvent
non-volatile solvent
Coagulation medium.
Warm Air
Spinneret in
coagulation bath
Wet spinning Dry spinning
Comparison of Solution Spinning
No phase separation
No non-solvent
No coagulation
No voidsExistence of voids
non-solvent involves
Phase separation

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Theoretical background of acrylic fiber
Nylon,polyester,PP,andpolyacrylonitrile.
Stabilityinthemoltenstage,
Polyacrylonitrilewouldnotmeltwithoutdecomposition,degradationofpolymer,
Lowcost,plasticsandrubbernatureintensiveresearchtofindasolventforpolyacrylonitrile
wasinitiatedbyanumberofAmericanandGermancompaniesinthe1940s.
extrusion
Organic solventsWet and dry-spinning
melt-spinning technology

6. Wet spinning of Acrylic fiber
6

7. 7
Schematic diagram of Wet spinning of Acrylic fiber

8. 20000–100000holeswithdiametersof0.05–0.25mm.
T°Cspinningdope&coagulationbath,25–125°Cand0–50°C,respectively.
Thespinneretisimmersedinthecoagulationbath=solidified
8
Conti….
Thesolidificationspeedisaffectedby:-
oTheconcentrationofthespinningdope,
oTheratioofsolvent/non-solventand
oThetemperatureofthecoagulationbath.
Easy flow of fluid vs Cohesiveness

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Workingprinciple

10. 10
solid polymer dissolved 1
solutionheatedintheheatexchanger2
solutionispassed/extrudedtospinneret3
Thefilamentwoundonthebobbin5
Wended filament is then drawn 6
washed & dried wound on a suitable package7
Delivery8
filamentofsolidform4
Spinning process

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A. Solvents/ non-solvent
Parameters of wet spinning of acrylic fiber
r,
Water Methanol,
Ethanol, 2-propanol

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B. Coagulation
Spinningdopeformgelfibersduetophaseseparationofthedopeinsolvent/watermixture.
Theinitialfiberformationperformedatexitsthespinneretscapillaries.
Counter-diffusionofthesolventfromthedopeandcounter-diffusionofthenon-solventfrom
thecoagulationbath,
Butitmayoccuratdifferentrates,whichdependon
20,000 to 100,000 capillaries
Mass transfer
Thecoagulationbathcompositionandtemperature
protofibers

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The Effect of Coagulation Variables
on Initial Fiber Structure
1.The effect of dope composition,
2.The effect of coagulation bath composition,
3.The effect of coagulant temperature, and
4.The Effect of Jet stretch

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1. The Effect of Dope Solids
Raisingdopesolids,improvesthehomogeneityofthefiberstructurebyreducingvoids.
Nosimultaneouschangeinthecross-sectionalshapeofthefiberoccurs,and
Solvent/polymer

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2. Effect of spin bath composition
Effect of spin bath composition on protofibrestructure at 55°C bath temperature

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3. The Effect of coagulation temperature
Dwell time
Retardation
Solidification speed

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4. The Effect of Jet stretch
Itistheratiooftakenoutofthecoagulationbathtodopeispumped
throughthespinneretholes.
Atagivensetofbathconditions,increasingjetstretchisaccompanied
bydecreasingdensity,decreasingsurfacearea,anddecreasethe
numberofvoids.

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C. Diffusion
Spinningsolutioncontactwithacoagulationbathdiffusionalinterchangeoccurs.
Duetoconcentrationdifferencesextrudeddopeandcoagulationproceedsattheexitofthe
capillary.
Solventleaves,whilenon-solvententers,
Afterasufficientlengthoftimenomoreexchangetakesplace,
Mass Transfer mixture of solvent and non-solvent
state of equilibrium
polymerphase

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Conti…
Diffusionprocessinfluencedby,
oSpinrate,
oDopeconcentrationand
oTemperatureofdope.
increase in temperature increases
the diffusion of solvent and nonsolvent
Increased polymer concentrations less solvent,
high rate of diffusion due to increase solvent out

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D. Phase Separation
Polymersolutiontoasolidphaseorporousgel
network.
Apolymerrichphaseandsolvent/non-solvent
phase.
Thevoidsareduetosolvent/non-solventphase
separationanddiffusionprocesses.

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E. Structure
Itisresultofthecounter-diffusionofsolventandnon-solventandthephaseseparation.
Gelnetworkofinterconnectedpolymerfibrilsseparatedbyvoid.
Thevoidsizeisdeterminedbytherateofdiffusionandphaseseparation.
Fibercrosssectioncanbealteredbychangingthecoagulationconditions.
Thevoidsizeincreasesastheratesofdiffusionandphaseseparationincrease.
size and number of voids dry, collapse, and relax VS

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Aftertreatments

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1. Washing
Fiberwashingwiththehelpoftemperatureandwashliquidconcentration.
Wateruseawashtemperaturelimitedtotheboilingpointofthewater.
Conductedmainlypreceding,orconcurrentwith,stretching.
Asmallamountofresidualsolventisusuallypurposefullyleftinfibertooptimize
processingbehavior.
Thefibrillarnetworkremainsaporousstructureatthispointintheprocessandgelstate.

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Fibersorientedthemolecularchains,whichresultedinanimprovementintenacity.
Diameteroffibersdecreased,andtheirsurfacesbecamesmoother
Theporositydecreasedandbecamemorecompact,
ThecrystallineorientationofPANfibersincreasedwithincreasingdrawratio.
2. Drawing
due to the draw ratio increases
improvementinthemechanicalproperties

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3. Finish
Achemicaltreatmentisappliedtothefiber.
Thechemicalor"finish"isnormallyanaqueoussolutionor
emulsionand
Ithasbothlubricantsandantistaticcomponentsthatfacilitate
fiberprocessinginthesubsequentcollapse/dryingstepsand
transformingthefiberintoyarnsandfabrics.

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4. Drying, Collapsing, Relaxing
Adrying/collapsingprocesspassingthefiberoverheatedzonesand/orhotrolls.
Whiledryingthefiber,collapsingisalsooccurringasthewaterisdrivenfromtheinternal
fibrillarnetwork.
Thefibercollapseistheclosureoftheorientedopenporestructure,
Therelaxationprocessisthefinalstepinchangingfibermorphologyandsignificantlyalters
thefiberstress-strainbehavior.
Ahot,wetenvironment;bothbatchandcontinuousrelaxationsystemsareutilized.
Externalandinternalfiberwater

27. Theconversionofpolyacrylonitriletofiberwasmoredifficultasthepolymerwouldnotmelt
withoutdecompositionwetspinningtechnologyforsuchfiberproduction.
Wetspinningbasicallyusedforpolymersthatneedtobedissolvedinasolventtobespun.
Thespinneretissubmergedinachemicalbaththatcausesthefibertoprecipitate,andthen
solidify,asitemerges.
Theonlydifferentfromotherspinningsolidificationduetocoagulationbaththatmakes
precipitatedfilament.
27
Summery

28. Reference
Dong,R.,Zhao,J.,Zhang,Y.andPan,D.,2009.Morphologycontrolofpolyacrylonitrile(PAN)fibersbyphaseseparationtechnique.JournalofPolymerScience
PartB:PolymerPhysics,47(3),pp.261-275.
Han,C.D.,&Segal,L.(1970).Astudyoffiberextrusioninwetspinning.II.Effectsofspinningconditionsonfiberformation.JournalofAppliedPolymerScience,
14(12),2999–3019.
Knudsen,J.P.,1963.Theinfluenceofcoagulationvariablesonthestructureandphysicalpropertiesofanacrylicfiber.TextileResearchJournal,33(1),pp.13-20.
Paul,D.R.,1968.Diffusionduringthecoagulationstepofwet‐spinning.JournalofAppliedPolymerScience,12(3),pp.383-402.
Masson,J.ed.,1995.Acrylicfibertechnologyandapplications.CRCPress.
Paul,D.R.,1968.Astudyofspinnabilityinthewet‐spinningofacrylicfibers.JournalofAppliedPolymerScience,12(10),pp.2273-2298.
Zhou,P.,Lu,C.,Shi,J.,Li,K.,He,F.,Zhang,S.andLi,Y.,2011.EffectofbathconcentrationoncoagulationkineticsattheearlystageduringwetspinningofPAN
copolymernascentfibers.JournalofMacromolecularScience,PartB,50(6),pp.1215-1225.
Peng,G.Q.,Wen,Y.F.,Yang,Y.G.,Liu,L.andWang,W.,2009.Effectofdopeextrusionrateontheformationandcharacterizationofpolyacrylonitrilenascentfibers
duringwet-spinning.Polymerbulletin,62(5),pp.657-666.
Arbab,S.,Noorpanah,P.,Mohammadi,N.andZeinolebadi,A.,2011.Exploringtheeffectsofnon-solventconcentration,jet-stretchingandhot-drawingon
microstructureformationofpoly(acrylonitrile)fibersduringwet-spinning.JournalofPolymerResearch,18(6),pp.1343-1351.
Han,C.D.andSegal,L.,1970.Astudyoffiberextrusioninwetspinning.II.Effectsofspinningconditionsonfiberformation.JournalofAppliedPolymerScience,
14(12),pp.2999-3019.
Knudsen,J.P.,1963.Theinfluenceofcoagulationvariablesonthestructureandphysicalpropertiesofanacrylicfiber.TextileResearchJournal,33(1),pp.13-20.
Wang,Y.-X.,Wang,C.-G.,Bai,Y.-J.,&Bo,Z.(2007).Effectofthedrawingprocessonthewetspinningofpolyacrylonitrilefibersinasystemofdimethylsulfoxide
andwater.JournalofAppliedPolymerScience,104(2),1026–1037.

29. Thank You for
your
kind attention!