Excluding those grinning factories which are either owned or controlled by the best practice spinning mills, majority of the remaining produce poor quality ginned cottons containing excessive trash and contaminations. High percentage of non-lint matter in Pakistani cottons is confirmed by the results of a quality survey conducted jointly by the Pakistan Central Cotton Committee (PCCC) and the Cotton Research Institute during 1998-99 [1]. These results are reported as under:

Samples containing higher than 5% NLC = 90%
Samples containing higher than 7% NLC = 56%.
Samples containing higher than 10% NLC = 11.50%

It is obvious from the above results that majority of cotton bales available to the spinning mills contain non-lint matter higher than 7%. It may be pointed out that non-lint content of American and CIS cottons is less than 4% and that of Indian cottons about 5%.

Inspite of very high NLC of Pakistani cottons, the spinning technologists working in the spinning sector are expected to produce at least seven bundles of yarn from one maund of cotton i.e. 70 lbs of yarn from 82.2857 LBS of cotton. The yield of yarn works out at 85%.

Thus, the spinning technologists face a challenging task! In order to reduce the end-breakages at the spindle point and yarn imperfections, the spinners must extract waste, micro-dust etc. at the blowing and carding stages effectively. For high spinning speeds, especially in open-end rotor spinning the trash content in card sliver must be in the range of 0.06% to 0.09% [2]. In order to produce card sliver conforming to such a high standard of cleanliness, the spinners monitor the waste extraction at the blowing and carding stages carefully. The break-up of waste extraction from blow-room to winding is reported as under:

1. Manufacturing wastes
Manufacturing wastes is an essential part of the process of conversion of cotton fibres into yarn. The percentage of manufacturing waste is proportional to the inherent trash content of cottons. As already pointed out NLC percentage of Pakistani cottons, in general is higher than 7%. It would be seen from the break-up of manufacturing wastes that the percentages are very high:

Useable waste = 4.20%
Unuseable waste = 15.25%
The yield of yarn works out at 80.55% much lower than the target of 85% expected from the spinners.

2. Improving yield
For improving yield of yarn a number of options are available to the spinners, some of which are discussed briefly as under:

2.1 Recirculation of useable waste
Recirculation of useable waste such as sliver and lap ends, sliver waste, roving waste after opening by roving waste opener and pneumafil waste is a normal practice in the spinning mills. These wastes are mixed in cotton at the opening and mixing stages in a sandwich manner before processing in the blow room. The object is to ensure homogeneous distribution of these wastes in the cotton mixing heap!

It is also important to keep the percentage of pneumafil waste as low as possible in the cotton mixing. It should not be allowed to exceed 3%. This is necessary because the cotton fibres in pneumafil waste after passing through all stages upto spindle point loose surface characteristics, i.e. convolutions, natural wax, pliability, etc. become brittle and are susceptible to breakage, nep formation at the carding stage and excessive end-breakage at the ring spinning frames.

Referring back to the percentage yield of 80.55% in case of processing 100% cotton, yield improvement by circulating useable (soft) waste is calculated as under:

Percentage of useable (soft) waste = 4.20%
Yield of yarn @ 90% = 3.78%
The yield of yarn will improve to 80.55 + 3.78 = 84.33%

2.2 Recirculation of unuseable waste
Recirculation of unuseable waste is normally avoided because it proves counter productive. However, during periods of scarcity of cotton due to one reason or another and abnormal escalation in cotton prices, the spinners are compelled to re-circulate unuseable waste. Blow room and lickerin droppings and card fly must be willowed. Loss in willowing can be upto 50%. Spinning mills equipped with combing sets produce noils (comber waste) which is a better option for re-circulation. Nevertheless, the yield of yarn from a mixing containing 75% cotton, 5% willowed blow room dropping, 5% willowed Lickerin dropping, 10% willowed card fly and 5% comber noils seldom exceeds 75%! Moreover, the yarns produced are generally in the coarse category i.e. 10 Ne or lower. The U%, number of imperfections are abnormally high and strength is low. The end-uses of such yarns are in the lower segments of the local market such as carpet weaving, bar mops etc.

3. Depressing factors
In order to improve yield of yarn in spinning mills, it is extremely important to control factors which depress yield. These factors are discussed briefly as under.

3.1 Moisture regain
It is a normal practice in the spinning mills to condition the cotton mixing for 24 hours before starting processing in the blow room. The object in to ensure that the moisture regain of cotton mixing is uniform throughout and is in equilibrium with the R.H.% of blow room atmosphere which is usually maintained at 40%. Cotton with moisture regain of 8.5% the internationally accepted figure dries upto 6.5%. The conditions in the card - section are also kept hot and dry similar to blow room so that extraction of waste is facilitated. The moisture regain in blow room laps is usually 6.0% which drops to 5.50% in the card sliver.

From the card sliver stage, the R.H. % at the drawing, roving, ring and cone winding is gradually increased to about 65% and temperature reduced to 95°F to accelerate moisture uptake by the material. The moisture regain in wound cones passed for conditioning in RG-1 is about 7.0%. The wound cones must be stacked in the conditioning room carefully to ensure all round exposure to humidified air. The best practice mills creel wound cones on pegs to increase exposure of wound yarn and improvement in moisture uptake. The duration of storage in the conditioning room should be from 24 to 36 hours so that moisture regain reaches the level of 8.5% originally present in cotton before packing of cones into yarn bags or cartons. By following this procedure any weight loss due to moisture regain being lower than 8.5% and consequent yield loss will be prevented!

It is extremely important that arrangement for humidification in the conditioning room is adequate. The best practice mills usually install mini-humidification plants called Saturation Ducts to ensure that moisture regain of yarn on wound cones is not less than 8.50% and no loss in yield of yarn occurs on this account.

3.2 Net yarn weight per bag / carton
As per market requirement, the net weight of yarn, per bag or carton after packing of 24 cones of yarn each with net yarn weight of 4.1666 lbs must not be less than 100 lbs. In practice it is almost impossible to pack cones in bags and cartons so that net weight of yarn is exactly 100 lbs. The reasons are:

· Variations in the actual count of yarn in the range of ±0.5 count which are unavoidable.
· Constant length of yarn wound per cone can be ensured within an accuracy of ±1.5% by means of settings of the length measuring monitors with which the modern winding machines are invariably equipped.
· Variations in the weight of paper cones are generally about ± 4.5% and cannot be avoided.
The spinning mills therefore carefully calculate minimum and maximum gross weight of wound cones and enforce tolerance limits for passing cones from winding department to conditioning rooms. These limits are usually - 35 gms to +20 gms and represent range of variations in the gross weight of cones calculated count-wise. The object obviously is that after conditioning and packing the net weight of yarn in bags or cartons neither exceeds nor falls below 100 lbs.

owever, in practice to ensure delivery of bags/cartons with net yarn weight not lower than 100 lbs, the average run of the spinning mills usually sustain a loss in yield of about 0.25 to 0.50%. Spinning mills therefore, do not purchase cotton lots with moisture regain higher than 8.5% and NLC higher than 7.0% as a matter of policy. In exceptional situations when such cotton lots have to be purchased, the price offered is proportionally discounted.

In conclusion, it may be pointed out that by re-circulation of useable waste, ensuring 8.50% moisture regain of wound cones and preventing weight loss in meeting the requirement of bags/cartons with 100 lbs of net yarn each, it is possible for the spinners to obtain a yield of 85% from poor quality ginned Pakistani cottons.

Acknowledgement
Useful technical information from M/s. Abid Umer, Bilal Akhtar, Tahir Hafeez and Muhammad Mobin (3rd year students) during the preparation of this paper is gratefully acknowledged.

References
1. Pakistan can earn more from quality cottons", report published in the Financial Post dated 15/5/2001.
2. Hermann Selker, "Top Technology in Blow Room and Carding to achieve High Standard in Export Quality", paper read at the International Conference on Textile Manufacturing - Technology for the 1990's, Lahore, 1991.

The case against King Cotton

The most potent test of American commitment to principles of fair competition, and to international trade law is the question that “Will the United States scrap its costly array of cotton-growing subsidies”

The question is of immense importance to impoverished farmers in places like West Africa, whose livelihoods are hurt by America's unfair, taxpayer - financed version of global trade. Brazil has mounted a strong legal challenge to America's cotton subsidies. There is nothing that creates more anger and disillusionment in poor and developing countries than the refusal of rich nations to play by fair rules when it comes to agriculture. The United States, Europe and Japan use government subsidies to make their farmer's products more competitive. In many cases, they wind up selling their produce for less than it costs to grow, elbowing other countries' goods out of the global market place.

Until now, the losers got no help from the WTO. At that body's inception in 1995, the wealthy nations rammed through a so-called peace clause that gave them the right to bend the rules as much as they wanted as long as their subsidies did not rise beyond the level of 1992. They argued that it would provide some time to address the issue through negotiations. But as the failed WTO talks in September in Cancun, Mexico, showed Europe, Japan and the United States are unwilling or unable to terminate the farm subsidies on their own. Fortunately, the peace clause will lapse next year, despite the attempts by Europe and America to have it extended. And Brazil's cotton challenge can proceed regardless because Washington's payments to cotton growers have exceeded the already astronomic 1992 levels.

American cotton costs a great deal to produce by international standards. Yet even though global cotton prices were crashing from 1999 to 2002, the U.S. share of global exports grew to 40%, from 25%. That was because Washington propped up King Cotton with $ 12.9 billion in subsidies. The United States was, in effect, paying the rest of the world to buy American product rather than the cheaper cotton grown in Africa and South America.

In recent arguments in its WTO case, Brazil offered credible expert testimony that in the absence of Washington's subsidies, America would have exported 40% less cotton. The cotton case shows that what the developing world needs is not a weaker trade referee, but a stronger one capable of standing up to rich nations.

Poor African farmers and American taxpayers stand to gain if the WTO does what Congress should have done long ago, and kills U.S. cotton subsidies and with the peace clause's retirement, more such cases should be brought against indefensible agricultural protectionism.

Courtesy: International Herald Tribune