Airlaid Web Formation Technique

PRINCIPLE OF WEB FORMATION IN A SIMPLE AIR LAYING PROCESS:

RAW MATERIAL: 

• Natural or man-made textile fibre (cut length >25 mm)
• Short cut fibres (generally <25 mm)
• Wood pulp (1.5–6 mm)

Air laid fabric compared with carding technology has these features: 

• The fibers are oriented randomly on the fabric surface – isotropic structure.
• Voluminious webs can be produced
• The range of the area weight is wider (15 – 250 g/m2) but the mass uniformity of light air laid (up to 30 g/m2) is bad.
• Wide variety of processable fibers

AIR LAID – PRODUCTION PROBLEMS: 

• Low level of opening fiber material by lickerin roller Thus is suitable to use pre-opened fibers or combine air laid with card machine – Random card machine.

• Variable structures of web in width of layer due to irregular air flow close to walls of duct . This problem requires high quality design of duct. 

• Possible entangling of fibers in air stream. This problem can be reduced by increasing the ratio air/fibers which nevertheless means decrease in performance and increase of energy consumption due to high volume of flowing air.

The relation between air flow and performance of device shows the importance of fiber length and fiber diameter. QA is air flow, K is device constant, P is performance of device (kg/hour), L is lenght of fiber staple (m) and D is fiber fineness (dtex).

QA = K.P.L2/D

Thus is suitable to use short fibers for this technology.

Random cards – combination of air laid and carding technology:

A major objective of this combination is isotropic textile fabric (random orientation of fibers) with good mass uniformity of light fabrics and with high production speed. 

• The first part – card machine opens perfectly fibrous material so single fibers are as a output.
• The second part – air laid system uses the centrifugal force to strip the fibers off a roller and. put them down on an air controlled scrim belt.

Main variations of random cards I. Airlaid function of random card:

1) Random roller between main cylinder and doffer, which rotate in the opposite direction of the main cylinder.

MAIN VARIATIONS OF RANDOM CARDS:

Main variations of random cards II:

2) Centrifugal force of mean cylinder strips the fibers off.

AIR LAID AND RANDOM CARDS: USED FIBERS: 
Synthetic fibres, viscose, cotton and blends thereof; natural fibres such as flax, hemp, sisal etc.; Reclaimed textile waste and shoddy, cellulose pulp 1.7 - 2000dtex. Max. 120 mm staple length

FEEDING SYSTEM OF RANDO WEBBER:

RANDO-WEBBER SYSTEMS WITH PERFORATED SCREEN:

RANDO-WEBBER SYSTEMS WITH CYLINDRICAL CONDENSERS:

Rando-webber:

• Relatively narrow widths up to about two metres
• Webs of 10– 3000 g/m 2
• Virgin or recycled fibres
• Filtration, home furnishings, automotive fabrics, insulation and some medical specialities

RANDOM CARD K12 OF DR. E. FEHRER:

HIGH-PRODUCTION RANDOM CARD K21 OF DR. E. FEHRER:

• K12 is more particularly suited to coarse fibres (10–110 dtex), Basic weight range 20– 2000 g/m 2
• K21 is more particularly suited to synthetic and viscose rayon fibers of (1.7–3.3 dtex), Basic weight range 10–100 g/m 2

SCHEMATIC VIEW OF THE DOA AIRLAYING SYSTEM:

SCHEMATIC VIEW OF THE AIR LAYING SYSTEM:

CHICOPEE AIRLAYING SYSTEM:

• Air velocity ( 140 m/s)
• Surface speed of the cylinder ( 20–60 m/s)
• Staple fibres ranging from 13–75 mm

SPINNBAU AIRLAYING SYSTEM:

THIBEAU HYBRID CARD AIRLAYING MACHINE:

Thibeau hybrid system: 

• Typical MD/CD ratio of 1.2–1.5:1
• Production rate of 200–260 kg/h/m
• Web weights of 35–200 g/m 2
• Fibre types cotton, viscose rayon, PET, PP, PA
• Fibre length of 10–40 mm.

“TURBO-UNIT”

TURBO-CARD RC 2-6 TR:

Turbo-Unit and Turbo-Card: 

• The turbo-unit TU is either fed by pre-carded webs via a feed plate intake or may be combined with a random card.
• The turbo-roll is equipped with carding segments.
• Aerodynamical web-forming by centrifugal force, doffer fan and suction conveyor
• Lower to medium fibre fineness range
• Staple length: approx. 10 - 80 mm
• Web weight: approx. 25 - 450 g/m 2
• Throughput depending on fibre fineness and fibre type: up to approx. 400 kg/h/m of working width
• Working widths: up to 4.000 mm
• Web speed: approx. 20 - 120 m/min

WEB FORMING MACHINE 008-0445 OF LAROCHE S.A.:

Laroche System: 

• Web weight ranges from 300 to 3000 g/m 2
• Production speed of up to 10–15 m/min
• Fibre length should be in the range 20–75 mm
• Cotton, man-made, glass fibres
• Hemp, flax, sisal, coconut
• Bed covers, mats, upholstery and insulation material, carrier material for carpets, industrial and geotextiles as well as furniture textiles

GENERAL PROPERTIES OF AIRLAID FABRICS: 

• HIGH ISOTROPICITY
• HIGH LOFT (IF REQUIRED)
• HIGH POROSITY (95–>99%)
• HIGH ABSORBENCY AND WICKING RATE
• SOFT HANDLE
• ADEQUATE TENSILE STRENGTH
• GOOD RESILIENCY (COMPRESSION RECOVERY)
• HIGH THERMAL RESISTANCE.

Air laid and random cards: end products:

• Chemical bonding: napkins, table cloths and wipes
• Thermal bonding: nappies (different components, i.e., acquisition layer, distribution layer and absorption core), feminine hygiene/incontinence products and insulation
• Spunlacing: wet and dry wipes for domestic and industrial applications medical textiles (including disposable gowns, curtains, wound-care dressings, bed sheets), filtration media
• Needle punching: interlinings and shoe linings, wadding, medical and hygiene products, geotextiles and roofing felts, insulation felts, automotive components, filters, wipes

Combination of unidirectional and cross directional web:

CROSSLAPPER WITH HORIZONTAL LAYING DEVICE:

Tasks of the web-laying machine:

• Increasing the web mass
• Increasing the web width
• Determining the web strength in the length and cross directions
• Improving the end product quality

LAP DRAFTER VSTG:

WORKING WIDTH UP TO 7.000 MM. INDIVIDUAL SERVO-DRIVES FOR 4 DRAFTING ZONES WITH INFINITELY VARIABLE DRAFTS. ONLY LITTLE CHANGES OF BATT WEIGHT REGULARITY BY FIBRE RE-ORIENTATION INCREASE STRENGTH IN MD.

MERITS AND LIMITATIONS OF CARD – CROSS LAPPING AND AIR LAYING:

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