nonwoven textiles basic course

8/6/2019 Nonwoven Textiles Basic Course

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Nonwoven Textiles

Basic course

1



Contents

• Definition of nonwovens

• Production, position and end-uses of

nonwovens

• Clasification of nonwovens

• Fibers for nonwovens, special fibers

•

Binder for nonwovens• Nonwovens technologies

2



Nonwoven definition (Europe)

• A sheet, web or batt – directionally orrandomly oriented fibers

• Bonded by FRICTION and/or

COHESION and/or

ADHESION

Excluded: paper, knitted, woven,…

3



Nonwoven definition (USA)

• A sheet, web or batt – natural or man-made

fibers or filaments

• That have not been converted into YARNS

•

Bonded to each other by any of several means

5



Production principles of nonwovens

• Web forming

• Web bonding

•

Fabric finishing

6



Web forming methods

- Dry Laid ( of staple fibers )

Carded, Air Laid, Combined Carded – Air Laid

- Wet Laid ( of staple fibres)- Spun Laid

Spunbond, Melt Blown, Electrostatic spun

7



Web bonding methods

- Mechanical bonding

Needled, Stitch bonded, Spunlaced, Felts

- Chemical bondingDispersion bonded by saturation, spraying,

screen printing, foam

Polymer solutions bonded- Thermal bonding by calender, thru-air,

ultasound, infrared

8



Finishing methods

• Coated

• Laminated

•

Crimped• Printed

• Special finished

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Nonwovens Growth in Regions 2006

0

2

4

6

8

10

12

14 Japan

North America

W-Europe

Rest of theWorld

Asia

Middle East

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11



Nonwovens

• Geotextiles, Agrotextiles

• Automotive

•

Hygiene (wet wipes, napkin, diaper)• Filtration

12



Fibers for nonwovens

• Polypropylene

• Polyester ( poly ethylene terephthalate)

•

Rayon ( Viscose)• Polyamide 6 ( Nylon 6), Polyamide 6,6

13



Basic parameters of staple fibers

• Linear density ( weight of 1000 m of fiber ingrams) 1,3-20 dtex

- Lenght of staple fibers

- For mechanical technologies 38-85 mm

- 2-30 mm for wet-forming

• Stress – strain behavior

• Fiber crimp

• Fiber finishings

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Special fibers

• Fiber with modified cross-section

• Bi-component fibers

a) Sheath/core b) Side by side c) Island in the

sea d) Orange

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Special fibers

• In bulk modified fibers- modify the fibre

properties

Non-flammable, UV-stable, antistatic and semi

conductive, antimicrobial, pigment

- Surface modified fibers

Metallized fibers, Silanized fibers

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Special fibers

• Glass fibers

• Basalt fibers

•

Carbon fibers• Metal fibers

• Aramide fies

• Novoloid fibers• Extremely strong polyethylene fibers

• Superabsorbent fibers

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Binders for nonwovens

• Polymer solution

• Polymer dispersion ( latexes )

•

Foamed polymer dispersions• Polymer pastes

• Solid polymers: Thermoplastic fibers

Thermoplastic powder, foil, meltblowns orspunbond sheet, netting

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Polymer dispersion ( latexes )

• An aqueous polymer dispersion is a two-

phases system consisting of homogeneus

phase ( water ) and particles of a polymer.

• A surfactant is an important part of dispersion.

• The surfactant prevents the particles from

unit.

• Surfactants are chamicals which reduce

surface tension on the surfaces between two

immiscible materials.19



Coagulation of dispersion

• Removing water, by evaporation for instance

• Increasing the kinetic energy of particles so

they are able to overcome electrostatic

repulsive powers and join together.

• Inhibition of surfatant dissociation which

results into loss of charge on the surfaces of

particles – by freezing of dispersion, by

dramatic change in acidity, by adding water

soluble salts, adding thermosensibilizers

20



Example of dispersion binders

The most important properties of binder are:

- Adhesion to the fibers

- Mechanical properties (stress-strain behavior)- Swelling and solubility in water and organic

solvent

21



Example of dispersion binders

• Styrene-butadiene copolymers

• Acrylic copolymers

•

Butadiene- acrylonitrile copolymers• Poly vinyl acetate and its co-polymers

• Polyurethane dispersions

22



Nonwoven Technologies

From staple fibers From polymer

Preparation of fiber materials Melting of polymer

Forming fiber layer Forming fibers and fiber layer

Bonding fiber layer

23



Web forming methos

Dry-laid methods :

Formation and layering carded web (mehanical

methods)

Aerodynamic web formation ( air-lay)

Combined mechanical-aerodynamic methods

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Mechanical methods

• Carding – In the carding process, individual

staple fibers are separated from clumps of

fibers and more or les uni-directionally

oriented

• Nonwovens- roller card

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Layering of carded web

• Longitudinal layering

•

Cross layering

• Perpendicular layering

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Longitudinal layering

27

12

3



Cross layering-horizontal cross-

lapper

29

f

ba

c

d

e

a) Web b) Feed belt c) Upper conveyor belt d) Lower conveyor belt

e) Delivery belt



Perpendicular laying

30

5

1) Carded web 2) reciorocating comb3) conveyor belt 4) wire grid 5) compresing bar



Perpendicular laying

31

7



Aerodynamic web forming

• Advantages are:

- Isotropic stucture of the web

- Voluminous webs can be produced- Wide variety of fibres processable as natural,

synthetic, glass, steel, carbon, etc.

32



Aerodynamic web forming

• The main disadvantages are as follows:

- Low level of opening fiber material by lickerin

- Various stuctures of web in width of layer due

to irregular air flow close to walls of duct

- Possible entangling of fibers in air strem

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Aerodynamic forming device

34

1) Condenser screen2) Lickering3) Condenser screen4) Fan

6) Duct



Combined mechanical-

aerodynamic methods

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The random card 1) Random roller 3)Condensing rollers2) Two doffer




aerodynamic methods

36

Three-cylinder principle




aerodynamic methods

37

1

Web former Fehrer K-21



Wet-laid methods

• Wet laid methods were developed as a

modification of the papermaking process.

• When compared with dry-laid methods, the

wet process are distinguished by:

- large, expensive and high-performance

devices, outpu speeds up to 1000 m/min.

- High demand on energy

- Lightweight, non-voluminous products,

usually below 100 /m2.38



Process

• Wet-laid process comprises the following

steps:

- Wetting and dispersing fibers in water

- Transport of fiber dispersion towards web-

forming device

- Forming fiber web on the moving endless wire

screen or perforated drum

- Removing water by suction, pressure and

drying39



Process ( Bonding)

• Hydrogen bonds when using self-bonding

cellulosic fibers or wood-pulp.

• Bonding dispersions applied before drying

process by spraying, printing,etc.

• Thermoplastic bonding fibers are admixed to

fiber material

40



Fiber

• The wood pulp, short cellulosic fiber, is a

typical raw material used in papermaking.

• Rayon, polyester, polyolefin and polyamid,

glass fibre

• Good wettability of fibers is necessary to

easily form water dispersion

• The tendency of fibers in the water dispersion

to cluster, entangle or flocculate is main

problem with the wet-laid process41



Fiber

42

• Length of staple 2-30 mm

• Concentration of fiber dispersion

• 0,005-0,05 mass percent of fibers are common

• Increasing the dispersion viscosity prevents

flocculation



Wet forming device

43

5

3

1) Dispersion inlet 2) Inclined wire screen 3) Dewatering pipes

4) Suction box 5) Formed sheet



Wet forming device

44

8

4

7

1) Dispersion inlet 2) Stirrer 3) Forming perforated cylinder

4) Formed sheet 5) Adjustable over- flow dam 6)Dewatering pipes7) Free dewatering 8) Suction dewatering



Polymer- laid method

• Spun bond

• Melt blown

• Electrostatic spinning

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Spunbonding process

• Operations:

- Polymer melting, transport and filtration of

polymer melt

- Filament extrusion

- Filament drawing

- Filament deposion- Bonding

46



Spunbond

• Any fiber-forming polymer such as

polypropylene, polyester, polyamide, can be

processed by spunbonding.

• The polymer pellets or granules are fed into

the extruder hopper. As the polymer moves

through the extruder, it melts due to the heat

and friction. Polymer melt is filtred .

47



Spunbond

• Filament extrusion- Spinneret is one of he

components of the die assembly. It is a single

block of metal having several thousands

drilled orifices or holes. Polymer melt is forcedtrough the holes and formed into filaments.

The fillaments are cooled by a stream of air

under the spineret.

48



Spunbond

• Drawing of the filaments follows spinning.

• The route e employes two blow ducts

49

C

Babcde



Spunbond

• The primary blow duct, located below the

spinneret, cools filaments. In the secondary

blow duct, located over the entire working

width of the producton line, a ventilatorgenerated under-pressure sucks filament and

air down from the spinnerets and cooling

duct.

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Spunbond

• The filaments are sucked trough a venturi

( high-velocity low pressure) zone to

distributing chamber, which serves to more

randomly move the filament around and to

some extent case then entangle.

- He filament deposition follows the drawing.

The filaments are deposited on the wirescreen conveyor belt usually in layers of

overlapping circular loops of filaments.

51



52

ab

c

d

h

a) Polymer meltb) Screen packc) Hole of spinneretd) Drawing jete) Drawing conduit



Spunbond

• Bonding:

- Autoadhesion

- Thermal bonding-calander

- Chemical bonding

- Needle punching

53



Spunbond

• Properties:

- Area weights between 5-800 g/m2

- Filaments diameters 15-50 micrometers

End-uses

- Geotextiles, portective medical, agriculturalapparel, top sheet for diapers, sanitary

napkins

54



Melt-blowing process

The melt blowing process consists of the

following integrated operations:

• Polymer melting, transport and filtration of

polymer melt

• Polymer extrusion and filament forming using

hot air

• Forming web on the surface of wire screen

collector belt-bonding

55



56

a

e

f

a) Extruder b) Gear pump c) Die d) Air manifolde) Collector drum f) Winder

Schematic of melt-blowing process



Polymers for melt-blowing procces

• Polypropylene

• Polyethylene

• Polyester

• Polyamide

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Schematic of melt blown die

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a) Inlet of hot air b) Inlet of polymer melt c) Cooling aird) Collector drum e) Fiber stream f) air knife g) Air angleh) Air gap



Bonding

• Self-bonding due to fiber entanglement and

cohesive sticking ensures sufficient cohesion

of the melt-blown web in many applications.

• Additional calander bonding is required in

some cases

59



Process variables

• The most important on-line variables of the

melt-blowing process and examples of their

typical values are as follows:

Temperature of polymer melt: 200-400 C

Temperature of air: 250-400 C

Air throughput rate: 100-500 m/s

Mass ratio air:polymer 100

Die-to-collector distance: 0,2-0,5 m

60



End-uses of melt-blown webs

The main applications of melt-blown webs are

- Filtration - thermal insulation

- Oil absorption - sanitary napkins

- Industrial wipes - respirators

- Adhesives - protective apparel

- Batery separtors - diapers cover stock- Surgical face masks, and many others

61



Web bonding methods

• Mechanical bonding methods

• Chemical bonding

• Thermal bonding

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Mechanical bonding methods

• Needle-punching

• Stich-bonding

• Spunlaced

63



Chemical bonding

• In chemical bonding, bonding adhesives are

used in the form of polymer dispersion ( latex)

or polymer solution

• Steps:

Forming fiber layer Apllication of binder,

Coagulation of binder Drying Curing

64



Methods of binder application

• The following methods of binder application

are used:

Saturation

Spraying

Printing

Froth bonding

65



Saturation

66

3

1) Fiber layer 2) Tank with circulation binder 3) squeeze rolls

Saturation applicator for pre-strengthened layers



Saturation

67

Saturation applicator for non-solidified fiber layers



Spraying

• The spraying process is employed mainly to

produce voluminous fabrics.

• It consists of spraying the binder on one or

both surfaces of the fiber layer

• A vacuum systém is usually employed to help

the binder particles to penetrate through the

thickness of the layer.

68



Spraying

• The binders are atomized in spray guns using

high pressure air or in spray jets using

hydraulic pressure.

• In the spray guns , latex and air are fed underthe pressure of 0,2-0,5 Mpa.

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Pneumatic spraying gun

70

2

1

2

2

2

1) Input of binder 2) Input of air

Spraying device with a spraying



Spraying device with a spraying

brush

1)Spraying brush 2) feeding roller 3) Bristel of spraying brush 4) Cover5) Adjustable part of cover 12) Fiber layer

nonwoven textiles basic course

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