Spun-bonding Process

     The spun-bonding process is specifically applied for spinning of synthetic filaments. Nonwoven formed by this process consists extrusion, drawing and laying of the filaments on a moving conveyor belt. 

Raw Materials 

Polypropylene, nylon, polyester, polyethylene and polyurethane are the best suitable raw material. 

• Polypropylene is the most widely used fiber, due to its low density. It is also available in various forms such as virgin fiber, dope dyed fiber, recycled fiber. Stability of the fiber to UV is low, creep resistance is low, and melting point is also low (160 °C).   
• Polyester is applicable where higher strength and UV resistance required. It has low resistance to alkali.
• Nylon 6 and 66 have higher moisture regain (4% at 65 RH and 70 deg.F) compare to other synthetic fibers, which makes nylon suitable for the spun-bonding. For nylon processing, cost of energy is high.
• Polyethylene is also used due to its low cost. It is limited due to its lower strength and low melting point (110 °C).
• Bicomponent fibers (Core/Sheath and side by side) can also be used for the process. These fibers can be produced by combining low melt polymer on the surface and high melt fiber in the core of the fiber. Eco-friendly fiber using polylactic acid (PLA) in core and polypropylene on the surface can be manufactured    

Batt manufacturing process

    Sequence for spun-bonding process is as follow:

        

All spinning technique can be applied for spun-bonding, like melt, dry or wet extrusion. But prominently melt spinning is applied. 

• Polymer chips are melted in extruder fed by the hopper.
• This molten polymer is filtered and extruded through the spinnerets. 
• Extruded fiber then quenched by the supply of cold air and oriented mechanically or pneumatically to increase the strength.

Polymer Melting: 

• Pellets, granules or chips of polymer are added in extruder hopper.
• By the means of gravity, polymer entered in heated barrel where rotating screw is also attached, from the hopper.
• Temperature of barrel melts the polymer, which generate the viscous form of polymer.
• The screw designed in three sections: feed, transition, and metering zones.
• In feed zone, polymer is preheated and transferred to the transition zone.
• In transition zone, polymer melts completely.
• This molten polymer is conveyed to the metering zone.

Metering of the melt:

• For proper filament extrusion, process parameters such as viscosity, pressure, and temperature are essential for a uniform flow of molten polymer.
• The same purpose is fulfilled by using a positive displacement volume metering device to deliver the polymer to the die assembly. 

Die assembly:

• The die assembly utilized for spun-bonding has two identical sections: the polymer feed distribution section and the spinneret section.
• Feed distribution section: 
• The polymer delivered by the metering device is supplied to all the spinneret through feed distribution section. 
• T-type and the coat hanger type system can be applied.
• Molten polymer directed into the spinneret from the same section.
• Spinneret:
• Spinnerets placed by side by side to produce a wide web (up to about 5 m) in commercial practice.
• The grouped spinnerets are also known as bank of block.   

Filament spinning, drawing and deposition:

• Filaments are drawn, entangled and deposited on to conveyer belt or collector.
• Proper filaments deposition based on aerodynamic principles for fanning and entangler.
• To increase cross-directional integrity of the web, fanning unit crosses or translates adjacent filaments.

Variants:

• In batt formation process, two variants are there, viz. Partial orientation and Full orientation.
• Partial orientation is suitable for most of the regular used products like cover stock for diapers and hygiene materials. It also provide high production rates and sufficient for required strength.
• Full orientation is applied for geotextiles, carpet backing, roofing and industrial products. 
• Full orientation can be achieved by drawing the filaments over heated godet rollers, with draw ratio of 1:3 or 4 with pneumatic acceleration.
• Then filaments are passed through a pneumatic air gun, where high velocity air is force with low pressure through a constricted area.
• During the drawing process, filament entanglements are avoided by applying electrostatic charges.
• Finally, filaments are deposited randomly or uniformly on moving conveyer belt.
• End use decides the lay down direction in both orientation variants.

The Production rate of spunbonding machine per meter working width in kg/hr

The mass per unit area of the web created on the perforated belt

Filament bonding and Staple fiber bonding:

Filament bonding		Staple fiber bonding
1.	Strength is high.	1.	Strength is low.
2.	Elongation is low.	2.	Elongation is high.
3.	GSM and thickness uniformity is higher.	3.	GSM and thickness uniformity is lower.
4.	Feel and textile character are lacking	4.	Feel and textile character are good.
5.	Tear strength is high.	5.	Tear strength is low.
6.	Product range GSM is 20-250	6.	Product range GSM is 20-1500
7.	Flexibility is lower in choice of raw materials.	7.	All types of raw material can be processed in the same line.
8.	Production is high.	8.	Production is low to medium.
9.	Investment is high at initiation step.	9.	Investment is low to medium at initiation step.
10.	Manufacturing process consist two steps.	10.	Manufacturing process consist single step.

Applications: 

• Industrial products
• Filters
• Cover stock for diapers and hygiene products
• Carpet backing
• Surgical Materials
• Bedding and furniture
• Geotextiles 
• Roof materials and other construction materials

References:

• Hosul Lim (2010), A review of spunbond process, J Text Apparel Technol Manage 6(3): pp 1-13
• Fourne F (1992), New process for spunbond fabric production. In spunbond technology today 2: onstream in the 90's (pp. 169-174), San Francisco.
• Gilmor TF (1992), Spunbond web formation process: A critical review. In spunbond technology today 2: onstream in the 90's (pp. 139-145), San Francisco.
• Karthik T., Prabha Karan C., and R. Rathinamoorthy (2016), Non-woven - Process, Structure, Properties and Applications, Woodhead Publication India, pp. 75-80.

      

Percentage Purity of HCl (Hydrochloric acid)

 

Process:

ð  Weigh 2 gm of the sample accurately in weighing bottle.

ð  Transfer the same sample in a 500 ml. volumetric flask.

ð  Made the solution up to 500 ml. with distilled water.

ð  Pipette out 10 ml. from the same solution using volumetric pipette and transfer it into a conical flask.

ð  Add 2 – 3 drops of phenolphthalein indicator.

ð  Titrate it against 0.1(1/10)N NaOH (sodium hydroxide).

    

     Chemical Reaction:

HCl_(aq) + NaOH_(aq) à NaCl_(aq) + H₂O_(aq)

Calculation:

Answer: % Purity of HCl is (BR) X 9.12

FLUOROSURFACTANTS

ð  Surfactants which contain one or more fluorinated or partially fluorinated hydrophobic groups are called fluorosurfactants or fluorinated surfactants.

ðThey show different properties than those of hydrocarbon surfactants.

ðHowever, like conventional surfactants, fluorosurfactants generally contain a hydrophilic groups and hydrophobic group within the same molecule.

ðThe hydrophobic group of fluorinated or semiflourinated surfactants can be linear or branched and may contain an aromatic group or additional elements as O, N, Cl, S and Si.

ðSome examples are,

C_nF_(2n+1)

C_nF_(2n+1)OC₆H₄^-

C₈H₁₇CH₂CH₂Si(CH₃)₂^-

Classification

            They can be classified according to change type of the hydrophilic groups.

(1) Anionic:-They contain (-)VE charge and so they are sensitive to pH and electrolyte concentration and may precipitate in water containing di- or tri- valent metal ions.

Examples are

Carboxylate           :-          R_fCOO^-M⁺

Sulphonates           :-          R_fSO₃^-M⁺

Sulphates               :-          R_fSO₄^-M⁺

Phospahtes            :-          R_fOP(O)O₂^-M₂⁺  etc.

Where, R_f is fluorinated or semifluorinated hydrophobic parts and M⁺ is an organic or inorganic counterion.        

(2) Cationic:- Like anionic, they are sensitive to pH and electrolyte content. The fluorinated hydrophobic is attached directly to quaternary ammonium group, a protonated group or a heterocyclic base.

(3) Non-ionic:- They include polyoxyethylene and polyoxyalcohols.

Oxyethylated alcohol                    :-          R_fCH₂O(CH₂CH₂O)_mH

Oxyethylatedthiol                         :-          R_fCH₂CH₂S(CH₂CH₂O)_mH

Fluorinated polyhydric alcohol     :-          R_fCH₂CH₂O[CH₂CH(CH₂OH)O]_mH

(4) Zwitter ion:- Over a pH as and their isoelectric point, they have zero overall charge but highly polar. They may function as either anionic or cationic depending upon pH of solution. Examples are,

Carboxybetaines   :-RfCH₂CH(COOCH₃)CH₂N⁺(CH₃)₂^-CH2COO^-

Sulphobetaines, sulphatobetaines etc.

Synthesis

            Most modern method of manufacture, involve reacting tetrafluorinatedethylene with a fluoride ion (Ca, K or tetraalkylammonium fluoride) in polar solvents (eg. DMF).

Polymerisation takes place and pentamer is used for further synthesis. This pentamer is coupled with phenol.

This phenol group can be sulphonated to give an anionic detergent.

    ðIt may be chlorosulphonated to give sulphonyl chloride, then treated with N,N’-dimethyl propane diamine, to give a tertiary amine and then quaternised with methyl iodide to give a cationic detergent 

 ðThe tertiary amine can also be reacted with propiolactone to produce an amphoteric surfactants.

Properties:- The unique properties are

ð  They have the surface tension of aqueous system to 2.0 N/m²

ð  They are effective even in the concentration of the order of 0.01 %.

ð  They show surface activity in organic system.

ð   They are chemically stable.

Applications

ð  They have excellent wetting properties.

ð  A fluorosurfactant treatment can make the textile resistant to wetting and penetration by both water and oil.

ð  They are used in emulsion polymerisation of fluoropolymer.

Reactive Dye (Fundamental)

ð  Reactive dyes are developed in the 1950s.

ð  Reactive dyes are mainly applied on cellulosic fibres such as cotton, viscose rayon, cuprammonium rayon, Wool, Nylon etc.

ð  Generally, these dyes are easily applied on cellulosic fibres and can be directly dyed from simple solution in water with alkali.

ð  These dyes chemically react with fibre forming covalent bond; hence they are sometimes called “Fibre Reactive Dye”.

Properties

ð  Reactive dyes are highly soluble in water. Solubility increases with the addition of urea.

ð  Reactive dyes are anionic in nature.

ð  Cold brand has higher affinity for cotton, so suitable for exhaust dyeing.

ð  Hot brand and Remazol are suitable for padding and printing due to their poor affinity for cotton.

ð  Reactive dyes show Excellent washing fastness (Except cold brands) & light fastness.

ð  Reactive dyes show poor bleaching fastness. (Bleaching Powder)

Structure of Reactive Dye

ð  Characteristic structural features of a reactive dye is shown below:- 

S = Solubilising Group like SO₃Na, or COONa, or combination of both

C = Chromophoric Group, responsible for affinity and diffusion of dye

B = Bridging Group, attach the reactive system to chromogen C

X = Reactive system, reacts with the functional group of fibre forming homo-polar bond 

Classification

Reaction Mechanism

ð  Cold brand reactive dye, being highly reactive due to presence of two chlorine atoms, it is more susceptible to hydrolysis and also possessing high fixation rate,

ð  One chlorine atom of dye attach to the functional group of fibre, while another one reacts with water.

ð  Reaction with water results into hydrolysis of dye, and so the wash fastness is poor as partially hydrolysed dye can not be removed from the dyed cotton.

ð  In hot brand reactive dye, only single chlorine atom is present, so it can either react with cellulose or with water. But do not stain adjacent ground.

Reaction with Cotton and Water

ð  Hydroxyl group present in cotton reacts with reactive dye with the liberation of acid, even at neutral pH.

ð  To increase the fixation, liberated acid must be neutralize with the addition of alkali.

ð  Hydrolysis process also produces acid, while reacting with dye.

ð  Rate of hydrolysis is very less to the rate of dyeing, with strictly controlling parameters of efficient dyeing.

 ð  Remazol dyes also react with cotton and water in same manner.

ð  Hot brand and Remazol react with cotton at primary hydroxyl group at C₆ position, while cold brand reacts with two different hydroxyl groups at a time.

  References

1) Fundamentals and practices in colouration of textiles by J N Chakraborty, Woodhead Publishing India, 2010, pp. 57-60

2)  Chemical technology in the coloration of textiles by S R Karmarkar, Colour publication Pvt ltd, 2007, pp. 181-187