Cotton hydrolysis

The ease of hydrolysis of a DMEU-treated fabric has been used to produce bicolored cotton fabrics. This was accompHshed by applying a thickened DMEU solution in a print configuration to the pile of fabric, curing the resin, and dyeing the fabric. The DMEU-treated areas resisted dyeing because of the cross-links. Subsequendy, the DMEU-crosslinks were removed via an acid hydrolysis and the entire fabric was overdyed to achieve the desired bicolored effect (69). 

Other Cellulosics. Rayon is bleached similarly to cotton but under milder conditions since the fibers are more easily damaged and since there is less colored material to bleach. Cellulose acetate and triacetate are not usually bleached. They can be bleached like rayon, except a slightly lower pH is used to prevent hydrolysis. The above fibers are most commonly bleached with hydrogen peroxide. Linen, dax, and jute requite more bleaching and mil der conditions than cotton, so multiple steps are usually used. Commonly an acidic or neutral hypochlorite solution is followed by alkaline hypochlorite, peroxide, chlorite, or permanganate, or a chlorite step is done between two peroxide steps. A one-step process with sodium chlorite and hydrogen peroxide is also used. 

Cellulose acetate [9004-35-7] is the most important organic ester because of its broad appHcation in fibers and plastics it is prepared in multi-ton quantities with degrees of substitution (DS) ranging from that of hydrolyzed, water-soluble monoacetates to those of fully substituted triacetate (Table 1). Soluble cellulose acetate was first prepared in 1865 by heating cotton and acetic anhydride at 180°C (1). Using sulfuric acid as a catalyst permitted preparation at lower temperatures (2), and later, partial hydrolysis of the triacetate gave an acetone-soluble cellulose acetate (3). The solubiUty of partially hydrolyzed (secondary) cellulose acetate in less expensive and less toxic solvents such as acetone aided substantially in its subsequent commercial development. 

Figure 12.30 Potential uses of polyphosphazenes (a) A thin film of a poly(aminophosphazene) sueh materials are of interest for biomedical applications, (b) Fibres of poly[bis(trifluoroethoxy)phosphazene] these fibres are water-repellant, resistant to hydrolysis or strong sunlight, and do not burn, (c) Cotton cloth treated with a poly(fluoroalkoxyphosphazene) showing the water repellaney eonferred by the phosphazene. (d) Polyphosphazene elastomers are now being manufaetured for use in fuel lines, gaskets, O-rings, shock absorbers, and carburettor eomponents they are impervious to oils and fuels, do not bum, and remain flexible at very low temperatures. Photographs by eourtesy of H. R. Allcock (Pennsylvania State University) and the Firestone Tire and Rubber Company.

The absolute configuration of C-3 of the chromophore 4 of an isopyoverdin was determined as S from the CD spectrum (Cotton effect -1-242 nm, —290nm, - -358nm) of 420 obtained from isopyoverdin by acidic hydrolysis (01T1019). 

Octamethyl pyrophosphoramide is a colorless oil, completely soluble in water, benzene, acetone, and many other common organic solvents except the paraffinic hydrocarbons. Its hydrolysis rate has not been measured, but it appears stable in the absence of alkali. In England, this systemic insecticide has been used to control aphids on hops. There it has been calculated that only a negligible quantity of the poison ultimately may find its way into the beer made from the hops. Despite calculations of this sort, the use of octamethyl pyrophosphoramide on food or fodder crops in this country is definitely not to be recommended. However, it may prove useful if properly applied to control certain insects, especially those attacking ornamental plants, such as rosebushes, and possibly on the cotton aphid and grape phylloxera. The compound has only recently been made available experimentally. 

The absolute configuration of C-3 of the chromophore 459 of isopyoverdins was determined to be S from the circular dichroism (CD) spectrum (Cotton effect +242 nm, —290 nm, +358 nm) of 460 obtained from isopyoverdin by acidic hydrolysis <2001T1019>. Diorganotin(iv) complexes with 4//-pyrido[l,2-/z pyrimidin-4-ones 461 <1996AOM47>, complexes of 2-methyl- and 2-methyl-8-nitro-9-hydroxy-4//-pyrido[l,2-tf]pyrimidin-4-ones with Ag(i), Cu(ll), Ni(n), Co(n), and Mn(n) ions <2000RJD587>, 2,4-dimethyl-9-hydroxypyrido[l,2-tf]pyrimidinium perchlorate and its complexes with prasedynium, neodymium, samarium, and europium <2000RJD310> were characterized by UV spectroscopy. 

Barsha and Hibbert16 also demonstrated by meins of methylation, acetylation, acetolysis and hydrolysis experiments that the membranes synthesized by the action of A. xylinum on D-fructose and on glycerol were chemically identical with cotton cellulose. 

Further work with the same dye (7.43) and carbodiimides (7.44 and 7.45) concentrated on this problem of limited efficiency. Cotton fabric padded with the dye phosphonate solution was aftertreated with the carbodiimide dissolved in various alcoholic solutions to avoid hydrolytic decomposition. Under these conditions cyanamide was much more effective than dicyandiamide. With conventional reactive dyes the efficiency of the dye-fibre reaction is limited by competing hydrolysis of the active dye. Although phosphonated or carboxylated reactive dyes do not hydrolyse, their level of fixation is limited by competing hydrolysis of the carbodiimide activator [46]. 

In a later development [136,137], cyanuric chloride was proposed as an aftertreatment for cotton already dyed with direct dyes containing amino groups. This approach appears even less likely to succeed than in situ addition to the dyebath. Serious hazards are associated with the handling of cyanuric chloride under these conditions. This highly reactive compound is a primary skin irritant and is known to cause severe allergic reactions in certain individuals. Dye-agent reaction will be inefficient because of hydrolytic deactivation. Uptake of cyanuric chloride (or its hydrolysis products) by the dyed cotton will be poor. 

The final product was subjected to ferric chloride-hydrochloric acid treatment in the same manner as commercial glucose and starch. A linear carbon dioxide-time relationship was observed which was practically identical with that for starch. In other words purified cotton cellulose, on relatively complete hydrolysis, appeared to give glucose in a... 

A recent modification of the hydrolysis-oxidation technique19 has produced strong support for the acid hydrolysis results already mentioned. In this instance samples of purified cotton linters were treated for varying times with boiling 2.5 N hydrochloric acid or with 2.5 N hydrochloric acid- 0.6 M ferric chloride. The latter was necessary where the hydrolysis extended over periods longer than 12 minutes and acted to hinder the formation of humic materials. By filtration and washing, a series of hydrocelluloses was obtained which corresponded to times of hydrolysis varying from 0 to 7 hours. 

Effect of Hydrolysis on Moisture-Regain (at 70°F., 65% rel. humidity) of Cotton Lintersl>... 

Fig. 3.—Effects of varying amounts of hydrolytic pretreatment on hydrolysis of cotton linters.

Nelson and Conrad29 have recently confirmed the viscosity behavior observed by Davidson26 and Nickerson and Habrle27 and have drawn a similar conclusion, namely, that after the rapid destruction of about 2 % of the intercrystalline network, hydrolysis occurs mainly on lateral crystallite surfaces. They also show that the apparent degree of crystallinity is reduced by fine grinding of cotton fibers. 

J. Koh, Alkali hydrolysis kinetics of alkali-clearable azo disperse dyes containing a fluorosulpho-nyl group and their fastness properties on PET/cotton blends. Dyes Pigm., 64 (2005) 17-23. 

Recommendation (Blue Grass) EH-2. Steps should be included in the processing of M1 propellant and M8 sheet propellant to prevent the persistent rayon bags or cotton threads from clogging or jamming the hydrolysis equipment. 

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