STOCKINGS

GENERAL PRINCIPLES FOR THE MANUFACTURE OF RAYON

The basic raw material of rayon is cellulose. Cellulose is the solid part or cell wall of plant life. Wood is composed almost entirely of cellulose. A special form in which it also occurs is the down or soft fibre around the seeds of certain plants. The latter form of cellulose is the purest known, and the processes that use this form obtain it from cotton seeds. As cotton fibre, is, in itself, an important textile, it is too valuable to be used for rayon, so its place is taken by what is known as cotton linters. The linters consist of short hairs which, after the removal of the longer cotton filaments, still remain on the seeds. Actually the linters are of the same substances as the cotton filaments; but they are too short for spinning into cotton yarn. At one time, these linters were left on the cotton seeds, as they could not be used for any other purpose; and a few of the Rayon Companies who produce the higher grade yarn have taken advantage of this form of cellulose, which, although cheap because it was a waste product, is the purest form of cellulose known.

The linters are removed from the cotton seed by a process called “ginning”. The Cotton filaments are pressed into bales and shipped in that form from their country of origin—usually from the U.S.A. Pine wood from Canada and Scandinavia is used to obtain the other form of cellulose used by the rayon industry. The logs are cut into six foot lengths and the bark removed. They are then cut into one inch wheels and broken up into small chips. Forty of those chips are then put into a “digester”—cylindrical boiler—chemicals are added and the chips boiled. They remain in the “Digester” for 24 hours. Then the chips are emptied into draining chests. From those they pass into sand traps—long narrow troughs in which they are cleansed of impurities. They are then bleached in large vessels called “Hollanders” and put on the drying machine—an endless belt of wire gauze. After being dried, they are compressed and cut into sheets. The mixture is then known as wood pulp and shipped, in cake form, to the rayon mills.

When the pulp sheets reach the mill, they are soaked in diluted caustic soda for several hours, and broken up into little

STOCKINGS

Two in particular stand out—Stern and Topham. It was Topham who invented the centrifugal spinning box—an invention which has been invaluable to the artificial silk producers.

After Swan came Cross and Bevan, who in 1892 took out patents for production by the Viscose process. In the same year Fremery and Urban manufactured artificial silk by the cuprammonium process in Oberbruch, near Aachen.

Over the next few years, artificial silk was commercialised. In 1901 the cuprammonium process was taken up by J. P. Bemberg, A.G., of Wuppertal-Oberbarmen. In the hands of one of their brilliant chemists, Thiele, this process was improved to such an extent that that Company’s particular cuprammonium yarn became known as “Bemberg”, after the name of the Company who patented those improvements.

In the meantime Courtaulds commenced to operate the viscose process in England; and during the year 1904, that firm started a new industry in England, just as J. P. Bemberg A.G., had started a new industry in Germany in 1901.

As usual, nothing did more for the development of artificial silk as a whole, than the competition which arose between manufacturers of the three different types. Competition became severe just after the 1914-18 War, when the Dreyfus brothers—two eminent Swiss chemists—entered the field. They began manufacturing in 1920 by a process called the acetate process, and in 1927 took over the British Celanese Company from the Government.

The word “rayon” is generally accepted to describe synthetic fibres of the cellulose type. It was introduced in 1924 in place of the older term “artificial silk” because rayon should be judged on its own merits, and not by comparison with other fibres. In rayon is seen a synthetic textile yarn made by man, and it therefore, is not a natural fibre.

The word “rayon” is now the generic term, for manufactured textile fibre, or yarn produced chemically from cellulose, or with a cellulose base, and for thread, strands, or fabric made therefrom, regardless of whether such fibre or yarn be made under the viscose, acetate, cuprammonium, nitrocellulose, or other processes.