Ammonia mercerization

Cellulose III. Cellulose III results from treatment of cellulose with Hquid ammonia (ammonia mercerization) or amines. Cellulose III can be made from either Cellulose I or II. When treated with water. Cellulose III can revert to its parent stmcture. Some cellulose III preparations are much more stable than other preparations. The intensities on diffraction patterns from Cellulose III differ slightly depending on whether the Cellulose III was made from Cellulose I or II, and thus these allomorphs are called IIIj or IHjj- Workers studying III concluded, based partiy on the results of I and II, that the packings of IIIj and IIIjj are parallel and antiparallel, respectively (67). IIIjj also is thought to have hydrogen bonds between the corner and center chains. 

Conversion to cellulose II and cellulose III via caustic mercerization and Hquid ammonia treatment are commercial textile processes that are discussed later. Figure 7 shows the characteristic diffractograms (CuKa radiation) of native cellulose, cellulose mercerized with sodium hydroxide, and cellulose treated with Hquid ammonia. 

Fig. 8. Internal volume (FQ that is accessible to sugars as functions of the cotton molecular diameters (33). (a) Batting A, greige , scoured—bleached , caustic mercerized H, Hquid ammonia treated, (b) Fabric 0> scoured—bleached V> cross-linked.

Scouting and bleaching slightly increase the accessible internal volume, Hquid ammonia treatment of the scoured—bleached cotton decreases it slightly, caustic mercerization substantially enhances accessibiHty, and cross-linking to impart durable press properties reduces this accessible internal pore volume substantially. 

Thus, further experiments were performed with two hydrolytically degraded linters powders subsequently disintegrated to different particle sizes (Filtrak, FNA and FND, VEB Spezialpapierfabrik Niederschlag, GDR), the lateral order of these samples being varied by liquid ammonia treatment or by mercerization with 18% aqueous NaOH. A posthydrolysis of these samples with aqueous acid (5% HC1, 2 hr, 100°C) resulted in changes in DP and in residue as indicated in Table IX and as to be expected from previous publications (11,16). 

Permanent press, 100% cotton fabrics are produced via a licensed process involving mercerization in a bath of liquid anhydrous ammonia. This Sanfor-Set process was commercialized in 197557. 

Variety Temperature Scouring and bleaching Caustic mercerization Liquid ammonia treatment Removal techniques... 

These techniques have been used to elucidate the effects of variety [289], temperature [287], scouring-bleaching [290], caustic mercerization [290-292], liquid ammonia treatment [290,292,293], cross-linking with different agents under varying conditions [294-298], dye-ability [296,299], and treatment with cellulases [300-302], on the cotton. The trends observed are summarized in Table 5.8. 

It has been suggested that the great depth of color or dye yield found with mercerized cotton is due to the caustic treatment inducing an abundance of large pores in the fiber. In contrast, the high level of resilience associated with liquid ammonia treatment has been ascribed to a low level of large pores in the fiber [292]. 

Strong alkali solutions acting on cellulose (at room temperatures) produce alkali cellulose. The studies on the structure of alkali cellulose [43] obtained with 20-40% NaOH solutions indicated that the substance is not a true alcoholate but an addition complex, RceiiOH NaOH. A true alcoholate can be obtained, for example, from dry cellulose and Na in liquid ammonia. Alkali cellulose has a large range of applications as an intermediate product in the preparation of cellulose ethers, and xanthate (dithiocarbonate), as well as in cellulose mercerization. 

The properties and swelling processes of cotton fibres after treatment with liquid ammonia are compared with conventional and hot mercerized cotton in Table 9.3. The nature of the improvement in properties resulting from the treatment of cotton with liquid ammonia depends on the conditions of its removal from the fibre. Dry removal of ammonia after treatment converts Cellulose I to Cellulose III,... 

In this test a mixture of red and green direct dyes is used to compare the maturity of cotton fibre samples. Immature fibres dye red, and mature fibres green. Mercerization increases the fibre s affinity for green compound and causticization number can be assessed related to the strength of the green hue. Fabric treated with liquid ammonia under industrial mill condition dyes red. 

The fibre is immersed in iodine solution (20 g iodine in 100 ml of standard KI solution) for 3 min and rinsed thoroughly. Mercerized cotton is stained bluish black and unmercerized cotton remains white. Cotton fibres in the yam bundle can be counted using a microscope and the ratio of dyed to undyed fibres can be used to determine the degree of mercerization. The iodine sorption value shows the largest increase for those samples treated in liquid ammonia with NH removal by evaporation, followed by caustic mercerized samples, and last by those samples NH treated and water quenched. Generally only minor differences in iodine sorption value are found between samples mercerized slack or under tension. 

Mercer, B. W. et al Ammonia removal from secondary effluents by selective ion exchange. J. Water Pollut. Control Fed., 42(2) R95—R107, 1970. 

Fig, 1.—Set of F our Diagrams from Ramie and Rayon Fibers, Corresponding to the Four Principal Polymorphs of Cellulose. ((A) Cellulose I (native) from purified ramie fibers, (B) Cellulose II (mercerized or regenerated) from Fortisan fibers, (C) Cellulose III (ammonia) from ramie fibers treated with ethylamine, and (D) Cellulose IV (high temperature) from fibers of ramie cellulose III treated with gIy< rol at 280 .]... 

Dilute alkali penetrates only accessible regions of the fiber causing intercrystalline or interfibrillar swelling. The latter is much more profound in that it brings about changes in crystal structure of the fibers, as evidenced by mercerization (in the case of alkali) and the formation of ammonia cellulose (in the case of liquid ammonia). 

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