Regenerated cellulose fibres

B. V. Hettich, "Regenerated Cellulose Fibres—Technology foi the Future," 30th Annual TPIMeeting 1980. 

This material has been known for many years, being used originally in the making of electric lamp filaments. In principle vulcanised fibre is produced by the action of zinc chloride on absorbent paper. The zinc chloride causes the cellulosic fibres to swell and be covered with a gelatinous layer. Separate layers of paper may be plied together and the zinc chloride subsequently removed to leave a regenerated cellulose laminate. 

Cellulose may be solubilised by treatment with sodium hydroxide and carbon disulfide. It can be regenerated by acidification of the solution. This is the basis of the production of regenerated cellulose fibre, so-called viscose rayon , which is a major textile fibre. The technique is also used for the production of continuous cellulose-derived film, so-called cellophane (from cellulose and diaphane , the latter being French for transparent). 

Table 12.12 Metal content of regenerated cellulosic fibres [146]...

Fixation in 6-12 hours with a mixture of sodium hydroxide and trisodium orthophosphate, a metering device being necessary. This method is recommended for regenerated cellulosic fibres. This formulation contains the same total amount of alkali as method (1) with the same bath stability, but may be preferred where some buffering capacity is required and sodium silicate is undesirable. 

Higher substantivity for cellulose. Dye at 45-50 °C with more caustic soda and less salt (none for mercerised cotton or regenerated cellulosic fibres). 

As the chain modulus of a polymer cannot be altered in a spinning process, a larger fibre modulus can only be obtained by improving the orientation of the chains and by an increase of the shear modulus g. However, there is one exception. After dissolving native cellulose fibres with the cellulose I conformation and a chain modulus of 138 GPa into a solution, the regenerated fibres obtained by spinning of this solution and subsequent coagulation always have the cellulose II chain conformation with a chain modulus of 88 GPa [26]. 

Cotton and Other Cellulosic Fibres. The dominant natural cellulosic fibre is cotton, the other natural cellulosic fibres, or bast fibres, include flax, linen, jute and ramie. The so-called regenerated fibres, which include viscose, modal fibres and lyoceU (Tencel), are made by various chemical treatments of cellulosic substrates. The dyeing and printing of cellulosic fibres and materials is carried out using, in decreasing order of scale and importance, reactive, direct and vat dyes. ... 

FIG. 13.93 Birefringence An as a function of the dynamic compliance E 1 = 5 for various regenerated cellulose fibres. 

The KAURIT types are either free or etherified N-methylol compounds of urea or of melamine. They are used mainly for the resin finishing of regenerated cellulose fibres, alone and in blends with synthetics. The term "self-crosslinking agents" characterizes their mode of reaction. 

In the crystalline part, the cellobiose units are closely packed to form Cellulose I in native cellulose fibres and Cellulose II in regenerated cellulose fibres. In Cellulose I the chain molecules are parallel to one another [16]. The folded chain occurs at Cellulose II, in the crystalline regions the chain molecules are antiparallel. Thus, the basis for helical structure for Cellulose I is preferably extended to the structure of Cellulose II [17]. 

Viscose rayon is inherently a weak fibre, particularly when wet, therefore it is highly susceptible to damage if enzymatic hydrolysis is not controlled. The enzymatic hydrolysis of viscose fibres causes a decrease of the intrinsic viscosity from 250 to 140 ml/g and an increase in crystallinity from 29 to 39% after 44 h [34]. Strong changes of the structure, however, are not typical for the enzymatic hydrolysis of cellulosic materials. Neither cotton nor wood pulp show an essential decrease of the DP during enzymatic hydrolysis [35-37]. The kinetics of the enzymatic hydrolysis of regenerated cellulose fibres before and after acid prehydrolysis changes the kinetics from a monophasic to a biphasic first order reaction [38]. 

Swelling of regenerated cellulosic fibres in caustic soda... 

Further tests for damage on regenerated cellulosic fibres, such as iodine absorption, core/sheath differentiation, peeling methods, detection of traces of sulphur or copper as well as some hints for investigations on bast fibres are given in the literature. ... 

As a result of these investigations it is generally agreed that naturally-occurring cellulosic fibres contain of the order of 60 to 70 per cent of molecules orientated in crystalline structure. The regenerated celluloses contain 30 to 40 per cent, Terylene 50 per cent, and nylon between 50 and 60 per cent. 

The success of the regenerated cellulosic fibres stimulated the imagination of chemists. The obvious sequel was to produce a regenerated protein with properties resembling wool or silk. Much research and capital expenditure has been devoted to the production of lanital from milk casein, ardil from ground-nut protein, saran from soya bean, and vicara from maize. None of them proved really commercially successful and their manufacture has now virtually ceased. 

The great demand for strong regenerated cellulosic fibres in the manufacture of motor car tyres created an outlet where high elasticity was not of such importance as in the manufacture of textile materials. Very great quantities of highly orientated viscose yarns are now manufactured for this end use. 

The advent of regenerated and synthetic man-made fibres has greatly increased the scope for making blends of two or more components. The oldest mixture of all is wool and cotton, which is used to ma e cloths known as unions. For this reason dyeing of mixtures of these two fibres is often referred to as union dyeing. There are three possible ways of dyeing mixtures of protein and cellulosic fibres ... 

In the first part of this chapter, a survey of the most relevant works regarding the use of different natural lignocellulosic products as a biosorbent for various organic pollutants is presented. The adsorption capacity, the pollutant model used, and their regeneration aptitude are reported. Then a detailed investigation of the different strategies of chemical modification carried in view of the enhancement of the adsorption capacity of cellulosic fibres, with the possible regeneration and reuse of the sorbent is fully described. 

The regeneration of saturated modified cellulose fibres has been carried out using water/ethanol solution. The new adsorbent can be regenerated easily and reused for multiple cycles of treatment without any reduction of its adsorption capacity. 

SOY 09] Soykeabkaew N., Nishino T., Peijs T., All-cellulose composites of regenerated cellulose fibres by surface selective dissolution . Composites A, vol. 40, pp. 321-328, 2009. 

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