Steps of Wet Processing Technology

Description and Working Principle of Scouring Process: Kier boiler is a long mild steel or cast iron cylindrical vessel provided with two perforated tube sheets disc with a number of hol

Steps of Wet Processing Technology

Prepared By : Mazadul Hasan sheshir ID: 2010000400008

13 th Batch (session 2009-2013) Department : Wet Processing Technology Email: mazadulhasan@yahoo.com

Blog : www Textilelab.blogspot.com (visit)

Southeast University

Department Of Textile Engineering I/A 251,252 Tejgaon ,Dhaka Banglade sh

Prepared By :

Total Textile Process at a Glance

Wet processing

  Desizing

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Scouring Process

There are two types of textile scouring processes –

1 Conventional scouring process:

• Kier boiling (discontinuous) scouring

• Scouring in J or L box (continuous)

• Exhaust method

2 Special scouring process :

• Solvent scouring process

• Vapor lock scouring proces

General recipe for scouring for Kier boiler process:

•Alkali (NaOH) - 2 to 5 gm per Litre. 

•Soda ash - x gm per Litre to adjust PH (PH required for  scouring is 10.5). 

Description and Working Principle of Scouring Process: 

Kier boiler is a long mild steel or cast iron cylindrical vessel provided with two perforated tube sheets (disc with a number of holes) One is placed at the bottom and another is top These discs are connected by a number of tunes which carry the liquor from the bottom compartment to the upper one In the middle compartment steam is passed Thus the tubes carrying the liquor are surrounded by steam which heats them

The hot liquor from the multitublar heater is sprayed over the cloth, packed in the kier, through a hollow perforated ring The liquid passes slowly over the packed cloth, collects below the false bottom, from where it is pumped into the auxiliary heater by a centrifugal pump and the cycle repeats

 Figure scouring process

Bleaching

• Bleaching improves whiteness by removing natural coloration and

remaining trace impurities from the cotton; the degree of bleaching

necessary is determined by the required whiteness and absorbency

Cotton being a vegetable fiber will be bleached using an oxidizing agent , such as dilute sodium hypochlorite or dilute hydrogen peroxide If the fabric is to be dyed a deep shade, then lower levels of bleaching are

acceptable However, for white bed sheets and medical applications, the highest levels of whiteness and absorbency are essential.

• Reductive bleaching is also carried out, using sodium hydrosulphite

Fibers like polyamide , polyacrylics and polyacetates can be bleached

using reductive bleaching technology.

• After scouring and bleaching, optical brightening agents (OBA), are

applied to make the textile material appear more white These OBAs are available in different tints such as blue, violet and red.

  Mercerizing process

Mercerizing is the process to improve the luster, hand and other properties of cotton by using strong caustic alkaline solution In this process, it can be divided into three uses that are dyeing printing, finishing and it also has been used in final appearance in

general.

Figure of Mercerizing process

Note: Fabric Mercerization

is Cheaper than double Mercerization which

provides a softer hand

  DYEING PROCESS

Dyeing is the process of give color to fibers, yarn, or fabrics by using

natural or synthetic dye [1] In this process it have involving three

principle process, that are retardation, migration and diffusion which all this are chemical process There are many type of dyeing that using

in textile wet processing such as cross dyeing, union dyeing and gel dyeing All of then has there own process to make the dyeing process smoothly and produce a good quality of dyeing.

Figure 6 : Type of a few color that use in dyeing process

Figure of dyeing process

Textile printing is referred as localized dyeing It is the application of color in the form of a paste or ink to the surface of a fabric, in a predetermined pattern Printing designs onto already dyed fabric

is also possible In properly printed fabrics the color is bonded with the fiber, so as to resist washing and friction Textile printing

is related to dyeing but, whereas in dyeing proper the whole fabric is uniformly covered with one color, in printing one or more colors are applied to it in certain parts only, and in sharply defined patterns In printing, wooden blocks, stencils , engraved plates, rollers, or silk screens can be used to place colors on the fabric Colorants used in printing contain dyes thickened to prevent the color from spreading by capillary attraction beyond the limits of the pattern or design.

Figure of printing machine

Finishing

• Textile finishing is the term used for a series of

processes to which all bleached, dyed, printed and

certain grey fabrics are subjected before they put on the market The object of textile finishing is to render textile goods fit for their purpose or end-use and/or improve serviceability of the fabric.

• Finishing on fabric is carried out for both aesthetic and

functional purposes to improve the quality and look of

a fabric Fabric may receive considerable added value

by applying one or more finishing processes.

or hydraulic pressure may be used as an alternative The pressure and heat applied in calendering depend on the type of the finish required.

The purposes of calendering are to upgrade the fabric hand and to impart a smooth, silky touch to the fabric, to compress the fabric and reduce its

thickness, to improve the opacity of the fabric, to reduce the air

permeability of the fabric by changing its porosity, to impart different degree

of luster of the fabric, and to reduce the yarn slippage.

An important and oldest textile finishing is brushing or raising

Using this process a wide variety of fabrics including blankets,

flannelettes and industrial fabrics can be produced The process of raising consists of lifting from the body of the fabric a layer of

fibers which stands out from the surface which is termed as "pile" The formation of pile on a fabric results in a "lofty" handle and

may also subdue the weave or pattern and color of the cloth.

There are to types of raising machine; Teasel machine and wire machine The speed of the card-wire raising machine varies from 12-15 yards per minute, which is 20-30% higher than that of teasel-raising That is why the card-wire raising machine is widely used.

Wet processing of textiles constitutes innumerable steps

leading to finished product, each having a number of complex variables and every lot is like a new lot and much depends on the well-trained manpower rather than modern machines and technology However, developments are taking place at a rapid pace to satisfy the user with quality product and competitive

price Though underlying principle for developments is

satisfying user needs This in turn will impart cost

competitiveness Then, more functional finishes are also being developed However trend is to use more mechanical finishes than chemical finishes The key to success in textile wet

processing technology will be the indication of highly trained manpower at lucrative wages in structured manner