Cellulose yarns

Geometric effects coupled with diffusion and nucleation usually control the rates of all solids deposition phenomena. Such effects can be put to good use in the production of special products such as cellulose yarn (rayon), by the precipitation of cellulose in filament form as it emerges as sodium cellulose xanthate liquid from the spinnerets into a bath containing sulphuric acid, which extracts the sodium as sodium sulphate, and the carbon disulphide. In a similar manner, the fabrication of aromatic polyimide fibres is performed by dissolving the polymer in concentrated sulphuric acid and forcing the solution through spinnerets into water. 

To dye the wool in a union without staining the cellulose, which may be either regenerated or natural, is comparatively simple. It is not very common for the wool to be dyed and the cellulose to be left white, but it is quite a general practice to incorporate a pattern constructed out of cellulosic yarns dyed in fast colours with an undyed wool background. The problem of dyeing such materials wool way is the same as leaving the other component white, because a non-staining method must be used. 

FI G U RE 10.44 Clearing temperature (Tc) as a function of polymer concentration for cellulose (DP = 800) in anhydrous phosphoric acid (74.4% w/w P2O5, solid circles). (From Boerstoel, H., Liquid Cystalline Solutions of Cellulose in Phosphoric Acid for Preparing. Cellulose Yarns, Ph.D. dissertation, University of Groningen, 1998.). Open circles represent the clearing temperature for poly(p-phenylene terephthalamide) (M, = 31,000 g/mol) in sulfuric acid (From Picken, S.J., Macromolecules, 22, 1766, 1989.). The square represents the clearing temperature for chitin (Af = 400,000 g/mol) solution at the polymer concentration of 15.5% w/w. 

FIGURE 10.45 Dry-jet wet-spinning process for cellulose solutions in anhydrous phosphoric acid (Akzo process). (From Boerstoel, H., Liquid Crystalline Solutions of Cellulose in Phosphoric Acid for Preparing. Cellulose Yarns, Ph.D. dissertation, University of Groningen, 1998.)... 

Boerstoel, H., Liquid Crystalline Solutions of Cellulose in Phosphoric Acid for Preparing Cellulose Yarns, Ph.D. dissertation, University of Groningen, 1998. 

Glycidyl trimethyl ammonium chloride cellulosic yarn treatment Benzoyl chloride cellulosics... 

Nitrolack cellulose silk Zellstoffseide cellulose yarn Zellstoffgam cellulosic fiber Cellulosechemiefaser cement (adhesive)... 

Increase of Water Affinity. The water imbibition of cellulosic fabrics is reported to be greatly increased v dthout increasing its resistance to creasing by an acid formaldehyde treatment in which the iinreacted formaldehyde and acid catalyst is removed before drying the fabric- . Results of this type are claimed for a process in v -hicL a cellulosic yarn is immersed in 30 times its volume of 40 per cent formaldehyde acidified with enough sulfuric acid to produce a normal acid solution and maintained at a temperature of 80°C for ten minutes. After this the fabric is washed in cold... 

Fig. 8 Tensile curves of cellulose II fibres measured at an RH of 65% (1) Fibre B, (2) Cor-denka EHM yarn, (3) Cordenka 700 tyre yarn, (4) Cordenka 660 tyre yarn and (5) Enka viscose textile yarn [26]. The solid circles represent the strength corrected for the reduced cross section at fracture. The dotted curve is the hyperbola fitted to the end points of the tensile curves 1,3 and 5. The dashed curve is the fracture envelope calculated with Eqs. 9,23 and 24 using a critical shear stress rb=0.22 GPa... 

In cellulose II with a chain modulus of 88 GPa the likely shear planes are the 110 and 020 lattice planes, both with a spacing of dc=0.41 nm [26]. The periodic spacing of the force centres in the shear direction along the chain axis is the distance between the interchain hydrogen bonds p=c/2=0.51 nm (c chain axis). There are four monomers in the unit cell with a volume Vcen=68-10-30 m3. The activation energy for creep of rayon yarns has been determined by Halsey et al. [37]. They found at a relative humidity (RH) of 57% that Wa=86.6 kj mole-1, at an RH of 4% Wa =97.5 kj mole 1 and at an RH of <0.5% Wa= 102.5 kj mole-1. Extrapolation to an RH of 65% gives Wa=86 kj mole-1 (the molar volume of cellulose taken by Halsey in his model for creep is equal to the volume of the unit cell instead of one fourth thereof). 

Fig. 29 The observed strength as a function of the initial modulus of filaments taken from a single yarn of cellulose II spun from a liquid crystalline solution compared with the calculated curves [26]...

Accessible Cellulose in Wood Pulp, Linters and Regenerated Cellulose. Crystalline Reactivity and Yarn Properties2S... 

P.R.170 is not always heat stable enough to allow application in polyolefins. In HDPE systems formulated at 1/3 SD, the pigment tolerates exposure to 220 to 240°C for one minute. Its tinctorial strength, on the other hand, is excellent. P.R.170 is also occasionally used in polypropylene and polyacrylonitrile spin dyeing in the latter medium, it satisfies the specifications of the clothing and home textiles industries. Besides, P.R.170 lends color to viscose rayon and viscose cellulose it is used for the mass coloration of semisynthetic fibers made of cellulose last but not least, it colors yarns, fibers, and films made of secondary acetate. 

McKelvey etal. (1959) investigated the reaction of epoxides with cellulose in alkaline conditions, reporting that alkaline cellulose reacted readily once the concentration of sodium hydroxide was sufficiently high. However, no evidence was found of reaction between cotton yarn and cellulose with a range of epoxides under a variety of reaction conditions. It was concluded that the apparent reactivity of cellulose with epoxides was primarily due to alkaline swelling of the cellulose, self-polymerization of the epoxide monomers then occurring within the interior structure of the fibres. It was also noted that the reactivity with phenol OH groups was very low (e.g. only 1 % conversion of ethylene oxide with various phenols). 

Acetic acid, CH3COOH, can be made by the oxidation of acetaldehyde, CH3CHO by catalytic addition of CO to methanol or by butane oxidation. Most acetic acid is used to make vinyl acetate or cellulose acetate, which are the intermediates for plastics, paints, adhesives, yarn, and cigarette filters. 

Before weaving, the warp is covered with a layer of polymer to withstand the mechanical stress (abrasion, tension) during weaving. These polymer coatings are so-called sizes. Normally native starch, modified starch like carboxymethyl-starch (CMS), carboxymethyl-cellulose (CMC), polyvinylalcohols (PVA), polyacrylates, and proteins can be used. The amount of added polymer for staple yarns like Co is between 8 and 20% of the weight of the warp. As a result, in many cases the final amount of polymer to be removed in the desizing step is approximately 5-10% of the weight of the fabric. 

Spinning of cellulose triacetate yarns follows the procedures used for the secondary acetate except that a different solvent is used. This is generally a 90 10 mixture of methylene chloride and methanol. 

The natural fibers obtained from cotton, wood, flax, hemp, and jute all are cellulose fibers and serve as raw materials for the textile and paper industries. In addition to its use as a natural fiber and in those industries that depend on wood as a construction material, cellulose is used to make cellulose acetate (for making rayon acetate yarn, photographic film, and cellulose acetate butyrate plastics), nitric acid esters (gun cotton and celluloid7), and cellulose xanthate (for making viscose rayon fibers). The process by which viscose rayon is manufactured involves converting wood pulp or cotton Iinters into cellulose xanthate by reaction with carbon disulfide and sodium hydroxide ... 

Rayon was first made by denitration of cellulose fibers (Chardonnet process). The cellulose was first reacted with a mixt of nitric and sulfuric acids to form NC, The prod was then dissolved in a mixt of eth and ethanol and spun into yarn by a "dry spinning process. In some instances the yarn was denitrated by alkaline hydrosulfites, neutralized and then w washed and dried (Ref 9). See also under "Cellulose Nitration, Denitration in Vol 2, C118-R to C119-R... 

Table VI. Properties of Cotton Cellulose—Polyvinyl Copolymera Yarns...

Table VIII. Rot Resistance of Cotton Cellulose-Polyvinyl Copolymer Yarns...

Table IX. Weather Resistance of Cotton Cellulose—Polyvinyl Copolymer Yarns...

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