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NYLON


ORIGINS & COMPOSITION OF NYLON


Ever since the beginning of the industrial revolution well over a century ago, the textile industry has been looked upon as an outlet for the ingenuity of the engineer, while the chemist occupied a position in the background, gradually coming to the fore with Artificial Silk during the years 1892-1905. In this, the youngest branch of the textile industry, however, the chemist has erected for himself a lasting monument in producing nylon, released to the world on October 27th, 1938, which is a new organic textile fibre derived basically from coal, water, and air, the process being as follows:-

When a dibasic acid and an organic diamine are heated together, the product produced by the reaction is called an “amide”. This reaction results in the formation of relatively small molecules which, when heated, bring about the union of many of these molecules, which form a chain, the molecule of a dibasic acid molecule linking up with a diamine molecule. When the chain is made up of many links, the resulting product is called a polyamide (“poly” meaning many). Such a product formed this way is called a “polymer”, and a long chain of polyamides is spoken of as “superpolymers”. The polyamide superpolymers are known as nylon.

Since there are dozens of different dibasic acids and diamines, it follows that many different types of nylon are possible. For example, if there were only ten different dibasic acids, and ten different diamines, it would be possible to make 10 x 10 (or 100) different nylons. The proportion of one to the other is important. For instance, one dibasic acid with two different diamines, would give another composition. An unlimited number of nylons is, therefore, possible. Some would be quite flexible, others would have a different melting point, and others would be stiff or rigid.

Since we are interested in nylon to be used in the manufacture of stockings, a particular type of polyamide—having the desired

STOCKINGS

assisted and speeded up by the flowing spinning bath. By this increase of speed, the filaments are drawn out very fine and leave the funnel with a diameter of about 0.01 mm. The whole process is known as the stretch spinning process; and makes “Bemberg” yarn the finest rayon yarn of the present day.

In order to obtain threads which are always the same thickness it is necessary that the same quantity of solution should be fed each time. This is ensured by a specially constructed precision pump, or spinning pump.

As already indicated, the fine separate filaments, which have been spun, are gathered together on leaving the funnel into the form of actual thread. The thread is drawn away from the funnel sideways and is thus separated from the spinning bath. It is then passed through diluted acid, which extracts further ammonia and copper, and thus completes the solidification of the thread, which is now taken up on a rotating reel.

Winding on to the reel is done in the usual way, with the use of a traverse which arranges the thread in a symmetrical criss-cross. To prevent the hanks becoming entangled, they are interlaced with tiebands.

The freshly spun thread is still by no means ready for use; it requires further treatment, which is given in the washing room. It is treated with different liquids in the washing machines, to free it from the last traces of copper sulphate, and is then washed in soap solution, which still further enhances its beautiful silky character. The hanks can then be dried. That is done in hot air dryers, into which the hanks are brought, hanging on rods. They are then placed in a conditioning room, which is a chamber kept at a constant humidity, from which they acquire a certain moisture content—about 11%.

The manufacture of “Bemberg” is then finished; and it is dealt with in the sorting department. The work is done by hand, each hank being hung over a horizontal rail and subjected to a careful inspection and grading by the girl sorters.