man made fiber spinning

Man Made Fiber Spinning

Prepared By : Mazadul Hasan sheshirID: 201000040000813th Batch (session 2009-2013)Department : Wet Processing Technology Email: [email protected] : www. Textilelab.blogspot.com (visit)

Southeast University Department Of Textile Engineering

I/A 251,252 Tejgaon Dhaka Bangladesh

Prepared By :

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Calssificatoin of fibres

Forms of Man Made fibre:

MMF are produced in three types –1. Filament:Filament fibres are spun from

spinnerets with 350 holes or less is determined by the size of the yarn to be made

Monofilament: This filament is made only of a single filament.

Multifilament: These filaments are made of more than one filament.

2. Staple:Staple fibre is of limited and relatively short length 3. Filament tow. An assemble of twist free fibre.

Properties required for Fibre forming polymer:

•Molecular weight should be high.•Crystallinity – high not suitable.•Resistance to different chemical.•Orientation – Physical and chemical symmetry.•Straight chain structure.•Glass Transition Temperature (Tg) – Should be near to Room Temp.•Crystalline Melting Point (Tm) - 200o – 300o c is suitable.•Polymer should be soluble in some solvent from which it can be spun.•Hygroscopic nature – Should be hydrophobic

Synthetic Spinning System

• Spinneret: A nozzle or plate provided with fire holes or slits through a fibre forming solution or melt is extruded in fibre manufacturing is called spinneret. This is the most important part of a MMF producing m/c. The number of holes, sizes and shapes vary with the filament desired.

• Shape of holes:Spinneret

Features of Spinneret:

Spinneret length:10-25 mmSpinneret diameter: 30-200 mmSpinneret thickness: 3.0 mmHole dia: 0.1.-0.8 mm

Problems: -Breaking (On account of high pressure and temp)Clogging (The holes can be blocked for solid particles

mix with polymer solution).Remedies:

-For breaking problem: the spinneret is to be changed.-For clogging: the spinneret should be cleaned after some days.

Number of holes in spinneret:

1. For monofilament: 1-3

2. For multifilament: 100-1000

3. Filament tow: up to 50,000

Flow chart of MMF production:

1. Manufacture of the fibre forming polymer.

2. Spinning ( extrusion through spinneret)

3. Stretching/Drawing ( improving strength and crystallinity)

4. Texturing/Crimping ( developing natural fibre properties)

5. Intermingling/Interlacing( applied instead of twisting)

6. Heat setting( made dimensionally stable)

7. Cutting: According to requirements.

1. Manufacturing of the fibre forming polymer:

• All man made fibres are composed of long chain molecules known as polymer which are formed by chemical processing.

• Common groups in polymers –– Amide or Peptide groups ( -CO-NH-)– Benzene ring– Ether linkage( -C-O-C-)– Ester linkage(-C-O-O-)– Hydroxyl group (-OH)– Nitrile group (-C-N-)

Spinning:

• The conversion of polymer into fibre is called spinning. The fibre forming substance is made temporarily fluid, extruded through spinneret and then returned to solid state (by solidification) in fibre form.

• Three types of spinning process:– Melt spinning (Synthetic).

– Wet spinning.

– Dry spinning.

SPINNING of polymers

There are typically three types of spinning for polymers: Melt, Dry and Wet. ▪ Melt spinning (Fig. 1) is used for polymers that can be melted easily. ▪ Dry spinning (Fig. 2) involves dissolving the polymer into a solution that can be evaporated. ▪ Wet spinning (Fig. 3) is used when the solvent cannot be evaporated and must be removed by chemical means.

Melt spinningIn melt spinning the fibre-forming material is melted and extruded through spinnerets, and the jets harden into solid filaments as they cool on emerging from the spinneret. Nylon is a melt-spun fibre.

Dry spinningIn dry spinning the fibre-forming substance is dissolved in a solvent before the solution is extruded. As the jets of solution emerge from the spinneret, a stream of hot air causes the solvent to evaporate from the spinning solution, leaving solid filaments. Acetate is dry spun by extruding acetone solutions of cellulose acetate into hot air.

Wet spinningIn wet spinning the solution of fibre-forming material is extruded into a coagulating bath that causes the jets to harden as a result of chemical or physical change.Viscose, for example, is wet spun. The solution of cellulose xanthate is extruded into an aqueous solution of acids and salts, in which the cellulose is regenerated to form solid filaments.

Man Made Fiber Spinning Technology

Man Made Fiber Spinning Technology

02. Spinning: Melt spinning:

• The process of spinning by which fibre or filament is produced from melted polymer chips by extruding through spinneret continuous filament produced here.

• Number of filament depends on number of holes in spinneret.

• It is the most critical operation in the production of nylon polyester, and polyolefin, poly propylene fibres as number of fibre properties such as uniformity, crystallinity, and orientation are imparted to the yarn during processing.


• .Feed

Melting

Cooling & solidification by

cold air.

Moisture conditioning

Lubrication

Yarn driving

Packaging

Flow Chart

Metered extrusion


Advantage:– Can be used for both staple and continuous filament.– Direct and simple process.– No environment pollution.– No solvent required.– Non toxicity and no risk of explosion.– High production speed (2500 – 3000 ft/min)– Low investment cost.

• Disadvantage:– Required more proper maintenance of the m/c. – Heat of input is high.


Typical melt spinning:Polymer Melting point Nylon – 6, 6 264oCNylon – 6 220oCPET 264oCPolypropylene 167oCPoly ethylene 125oC

02. Spinning: Dry spinning:

• In dry spgn, the fibre forming polymer dissolved in a volatile solvent is introduced into a heated drying chamber where the solvent is evaporated and solid fibre is obtained through spinneret.

• This process is used for Acetate and some polyacrylonitrile fibre.


• Dry spinning solvent:Fibre SolventI) Cellulose -Acetone + (2-6) % waterII) II) Triacetate -Methylene chloride (40%) +

Methanol (10%) III) Poly acrylonitrile -Di-methyl formamide or

Dimethyl acetamide.IV) Spandex - DMF, DMAC.V) Modacrylic - Acetone.


• . Feed

Metered extrusion

Solidification by solvent

Evaporation

Lubrication

Yarn driving

Packaging

Dry spinning Process


• Advantage: – Suitable for producing fine denier fibres.– No need of wash of fibre.

• Disadvantage:– Investment cost is high.– Toxic and risk of explosion.– Heat input is very high.– Can not be used for staple fibre production.

• Properties of solvent:– Solvent should not be volatile.– It should be organic.– It should have low boiling point.– It should be comparatively cheap.– It should be thermally stabilized.– It should be non toxic.

02. Spinning: Wet spinning:

• In wet spinning a suitable solvent is used to prepare fibre forming solution and another coagulant is used in coagulating bath.

• Solution is extruded through spinneret and in contact of coagulant cellulose is regenerated.

• Wet spgn solvent & coagulant: Fibre Solvent Coagulant Viscose Alkaline water Dill H2SO4 + Na2SO4 +ZnSO4

PVA Water Aqueous NaOHPAN DMF/DMC + Aq DMF/DMC + 40% ZnCl2

• 60% ZnCl2


Coagulation bath Washing Bath


• Advantage:– Suitable for staple fibre.– Both organic and inorganic solvent can be used.– Low temp reqd.– Higher production due to continue spgn.– Softener process.– Investment cost is low.

• Disadvantage:– Slow spgn speed.– Washing and bleaching of fibres are needed.– Toxic.

02. Spinning: Difference

Parameter Melt spgn Dry spgn Wet spgn

1. Investment cost Low High Low2. Hazard Non toxic Toxic Toxic3. Heat of spgn High Very high Low4. Spinneret hole 2 – many

thousands300 – 900 20000 – 75000

5. Spgn speed 2500 – 3000 ft/min

2500 – 3000 ft/min

150 – 300 ft/min

6. Productivity High Low High7. Application Filament or

staple Filament Filament or

staple

8. Solvent Not required Only volatile organic solvent

Both organic and inorganic solvent can be use.

Features Melt Dry Wet

Investment Cost Low High Low

Hazard Non-toxic Toxic(Risk of

explosion)Toxic

Heat of Spinning High High Low

Spinneret Hole 2 to many thousand 300-900 20,000-

75,000

Spinning Speed 2500-3000 ft/min

2500-3000 ft/min

150-300 ft/min

Comparative features of melt, dry and wet spinning

•Production does not depend on climate & location.

•Quality & quantity can be controlled during production.

•Length & thickness can be controlled as per requirement.

•Staple length can be controlled as per requirement.

•Smoothness and high luster.

•Fiber processing is easier.

•High productivity and low cost.

Advantage of man-made fiber technology:

1. Fabrics made of MMF are difficult to stitch.

2. Low air permeability.

3. Uncomfortable.

4. Unhygienic.

5. Hydrophobic.

Disadvantage of man-made fiber technology:

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