Wool manufacturing

WOOL MANUFACTURING

After the manufacturer purchases wool, it must be passed through a number of processes before it takes the form of a fabric. Even though grading of wool has been done previously, the wool must be sorted individual fleece-wise to obtain greater uniformity. The wools are processed on woollen or worsted systems.

A. Oiling of the wool : The wool is first lubricated with oil to minimize the breakage of wool fibres in carding, reduce the fly waste and static electricity in carding and increase cohesion of the fibres in loose sliver, thus facilitating drafting and spinning. Mostly non-ionic mineral emulsified oils are used in the strength of 3-5 per cent of wool weight. Mahua oil emulsified with soap is extensively used in India. In worsted processing, usually 0.5 per cent or even less oil emulsion is applied.

B. Woollen carding and spinning : Carding is the next process after drying. This is done by passing the wool between the cylinders which have fine wire teeth and which revolve at different speeds. The wool comes from the cards in a fluffy rope-like roll in which fibres lie in all directions. Woollen carding is done to further open the wool, disentangle locks, straighten the individual fibres, remove natural impurities, further mix the stock and deliver it in a convenient form for transfer to the spinning frame. These objects are accomplished by 2-, 3- or 4-card systems. The woolen yarn is spun either on mule or ring spinning frame.

C. Worsted carding and spinning : Properly lubricated wool is subjected to worsted carding where wool fibres are placed parallel to each other and the impurities removed. These fibres are arranged into a continuous sliver of definite weight and thickness. The carded slivers are grilled on an auto-leveller to improve the parallelization of the fibres ready for combining to produce a homogenous mixture of fibres and to deliver the sliver of uniform weight distribution. Wool combing is done to remove the short fibres and vegetable matter, and ensure parallelization of the fibres. The combed material is usually termed as “top”. After combing, top finishing processes are employed to obtain sliver regularity, desired sliver weight, retain the parallel state of fibres, and wrap the sliver so that it forms a suitable package. Worsted yarns are known for their regularity, uniformity and strength, and are used for suitings, shirtings, knitwears and knitting yarns either in single or in twisted ply.

D. Weaving : Weaving of yarns involves a series of preliminary processes which include cone winding, warp preparation, warp sizing, pirn winding of welt yarns, tying in and drying in of warp. Various types of looms are used, all of which have 3 common basic motions viz. shedding, picking and beating, besides 2 secondary motions viz. let off and take up. All these motions play a vital and basic role in fabric weaving.

E. Dyeing : In earlier days, wool was dyed with dyes produced from plants and animals. Dyes used for wools presently are classified into acid dyes, metal-complex dyes, chrome dyes, vat dyes, reactive dyes, and direct dyes. Wool can be dyed in loose stock, top yarn and piece goods.

F. Finishing : The objective of finishing is to improve the cloth as received from the loom, thereby rendering it more acceptable to the buyer and more suitable for the intended purpose. The factors involved in finishing vary depending upon the type and quality of raw wool used, the type of yarn used in the fabric, the design and structure of the fabric, and the specified surface character and handle to which the fabric must adhere. The preliminary processes which have to be taken up before the actual finishing process are : numbering, weighing, perching, picking, knotting and mending. The steps involved in finishing are :

a) Milling : It is the process of shrinking the fabric to the required degree, thickening it, and giving it the desired appearance and handle. The milling machines are of two types : stock and rotary. The rotary types are widely used.

b) Raising : This consists of lifting out from the body of the fabric. This action is simply to entangle the fibres with sharp points of wire rollers and bring them to the surface of the fabric.

c) Shearing : It is performed to remove the protruding fibred from the cloth surface or to even out or level the fibre pile which has been previously raised by brushing or steam brushing. Dry decanting generally follows shearing. For a high lustre finish, it follows pressing and subsequent cooling. This produces a permanent setting of the fabric.

Other specialized finishing processes include permanent press, lustring, stretch fabrics, water-repellant and stain-resistant treatments, moth proofing and shrink proofing.