Reference Book for Man-Made Fibres | Cesare Andreoli and Fabrizio Freti

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Reference Book for Man-Made Fibres
By Cesare Andreoli and Fabrizio Freti
Reference Book for Man-Made Fibres

Introduction
I am pleased to present the fifth “Notebook” on textile machine technologies, which Fondazione ACIMIT decided to prepare for the Italian textile technical institutes.

The subjects of this Notebook are the machines and the technologies for the processing of “manmade fibres”, an industrial sector which sees Italian companies and their know-how holding an unquestionable leading position, also at international level. The Notebook offers a wide and thorough survey on the main types of man-made fibres, both artificial and synthetic. Its realization had been entrusted to a qualified textile organization, Centro Tessile Cotoniero e Abbigliamento at Busto Arsizio (Varese), which gladly took on this demanding task.

This Notebook, which is dedicated to “man-made fibres”, follows up the Notebooks reserved to “spinning”, “weaving”, “knitting” and “finishing” technologies, all of which found such a favour, as to justify the publication of a second and even of a third edition, for a total of 14.500 copies.

The success of this initiative convinced us also of the opportunity to translate the Notebooks into English, in order to ensure their circulation also beyond the Italian borders with the leading textile institutes and universities. Moreover, considering the very high vocation and the age-long tradition of China as a textile country, we decided to publish also a Chinese edition.

The exigency of realising the Notebooks came from a series of meetings which Fondazione ACIMIT started with the headmasters and with the teachers within the framework of the various undertakings aimed at developing relations with the school world.

In fact we had been informed that the text-books presently available were not updated to the steady and rapid technological development which characterized the textile sector in these years. We of course welcome any suggestion and correction which the teaching staff, the company technicians, etc. might address to us in order to enable improving further the service offered by these publications.

CONTENTS
Part I – Introduction – Generalities
A survey of man-made fibres history ....................................................................6
Production data .....................................................................................................9
Fibre classification...............................................................................................15
Part II – Production processes
Polymerization ....................................................................................................16
Spinning...............................................................................................................20
Drawing ...............................................................................................................25
Part III – Textile processes
Texturization........................................................................................................35
Twisting ...............................................................................................................52
Production of discontinuous fibres: tow-to-staple, tow-to-top ............................64

A survey of man-made fibres history
Man-made cellulose fibres

The first man-made fibres which were developed and produced used polymers of natural origin, more precisely of cellulose which is a raw material available in large quantities in the vegetable world. The beginning of industrial production of man-made fibres goes back to the year 1890, when the French Count Hilaire de Chardonnet started up his plant for the production of “Chardonnet silk” (initial output: 50 kg per day), using the cellulose nitrate process.

As it happens in general in the case of technical-scientific developments, this achievement was the result of previous studies and researches (since approximately the year 1840) focused mainly on the chemical properties of cellulose.

In particular the researchers found the way to treat cellulose (a material insoluble in usual solvents and inflammable) with nitric acid (nitrification), to dissolve the derivative with solutions of alcohol-ether, to prepare suitable extrusion devices (spinnerets) and finally to regenerate cellulose through saponification in alkaline baths (denitrification) in order to eliminate the danger inherent in the nitro compound (inflammable and explosive).

Actually the birth date of the “artificial silk” (such was the name given to this fibre at its introduction) is said to date back some years before (1884) when an Englishman, Mr Swan, produced small quantities of nitrocellulose which the researcher gad in mind to use for the development of incandescent bulbs.

More or less in the same period another way had been searched for to make cellulose capable of being spun, after being discovered that cellulose could be dissolved in a mixture of copper oxide and ammonia (Schweitzer’s reagent, 1857).

In fact this principle had been the basis in Germany for the production initially of incandescent bulbs (1891), then of cuprammonium fibres (1897) via the so-called “cupro” process, which was improved with the draw-spinning process (1891) and resulted in the production of Bemberg cupro yarn in 1909.

Meanwhile a patent had been registered in England by the researchers Cross, Bevan and Beadle (1892) for the production of sodium cellulose xanthate and for its dissolution in dilute caustic soda. In this way the bases were laid for the production of a man-made cellulose fibre, now called viscose, which remained for decades the main process in use for the production of manmade fibres.

The first industrial plants were built some years later in England and in Germany (early 1900), and contributed to the rapid decline and giving up of the Chardonnet process, which was left off in Germany in 1911).

One of the various chemical properties of cellulose which found particular interest was the possibility of esterificating with acetic acid the three hydroxylic groups contained in the glycosidic group of cellulose; the first product to be obtained was triacetate (1894) which, as it was later on discovered, could be partially hydrolized (1905) into a product which was easily soluble in acetone.

However only later on the most was made of the capacity of cellulose acetates to be transformed into fibres; the fibre which attained more relevance was cellulose diacetate (1919-1921), commonly named acetate, whereas triacetate (produced since 1914) found limited commercial interest owing to its difficult dissolution, restricted only to chloroform.

Cellulose fibres were produced with said processes in form of continuous filament yarns, as the primary objective of the researchers was the reproduction of the morphology and, at least partially, of the properties of raw silk (from which the term “artificial silk” originated). In 1920 the fibre was made available also in form of staple fibre (“Vistra”, Germany) and as such attained in time relevant market importance.

Recent years saw the development of a process for the production of cellulose fibres using a solvent specifically studied for cellulose (N-methylmorpholine-N-oxide), which on one hand safeguarded to a greater extent the inherent properties of the original cellulose structure and on the other permitted the use of processes less polluting than traditional ones. In this connection we cannot but emphasize the role played by the Italian industry within the sector of cellulose fibres.

The first factories sprang up at the beginning of last century thanks to the initiative of French chemical groups and in 1914 could supply 150 tons of rayon (this was the name given to the continuous filament fibre).

The first post-war period saw the successful coming on stage of the company SNIA which, through the concentration of various production units, became at the end of the 20’s one of the major world producers of viscose rayon and later on of viscose staple fibre.

In 1927 the production of cuprammonium yarn was started on behalf of the company “Seta Bemberg S.A.”. In short, the Italian production rose from 320 tons in 1919 to 32,500 tons in 1929, so that Italy became the leading producer in Europe with a 16% share on world production. At the outbreak of the 2nd World War the Italian production had reached 120,000 tons.

The post-war period recorded a recovery of this industry, which reached its peak with 226,000 tons in 1964; from that date on, at first slowly and later at a quick pace, artificial fibres made room for synthetic fibres. As regards artificial fibres, it needs to be reminded that this group of fibres includes also fibres which have as raw materials natural polymers other than cellulose, like fibres derived from proteins.

A considerable historical significance was attained in Italy by protein fibres derived from casein, which were produced initially by SNIA in 1936 (researcher: Ferretti) under the name Lanital, later on renamed into Merinova.

Protein fibres of animal origin (casein from milk) stopped to have commercial significance, whereas still to-day a certain interest is enjoyed, especially in USA, by protein fibres of vegetable origin (maize, peanuts).


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